Development of an in-situ calibration device of firn properties for Askaryan neutrino detectors - Anker, Astrid; Baldi, Pierre; Barwick, Steven W.; Beise, Jakob; Bernhoff, Hans; Besson, Dave Z.; Bingefors, Nils; Cataldo, Maddalena; Chen, Pisin; Fernández, Daniel García; Gaswint, Geoffrey; Glaser, Christian; et al. (Proceedings of Science, 2022)
High energy neutrinos (E >1017 eV) are detected cost-efficiently via the Askaryan effect in ice, where a particle cascade induced by the neutrino interaction produces coherent radio emission that can be picked up by antennas installed below the surface. A good knowledge of the near surface ice (aka firn) properties is required to reconstruct the neutrino properties. In particular, a continuous monitoring of the snow accumulation (which changes the depth of the antennas) and the index-of-refraction profile are crucial for an accurate determination of the neutrino’s direction and energy. We present an in-situ calibration system that extends the radio detector station with a radio emitter to continuously monitor the firn properties by measuring time differences of direct and reflected (off the surface) signals (D’n’R). We optimized the station layout in a simulation study and quantified the achievable precision. We present 14 months of data of the ARIANNA detector on the Ross Ice Shelf, Antarctica, where a prototype of this calibration system was successfully used to monitor the snow accumulation with unprecedented precision of 1 mm. We explore and test several algorithms to extract the D’n’R time difference from noisy data (including deep learning). This constitutes an in-situ test of the neutrino vertex distance reconstruction using the D’n’R technique which is needed to determine the neutrino energy.
CRIS-Team Scopus Importer:2023-08-15

DEVELOPMENT of the MODEL of GALACTIC INTERSTELLAR EMISSION for STANDARD POINT-SOURCE ANALYSIS of FERMI LARGE AREA TELESCOPE DATA - Acero, F.; Ackermann, M.; Ajello, Marco; Albert, A.; Baldini, Luca; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, Elisabetta; Bloom, E. D.; Bonino, R.; et al. (Astrophysical Journal Supplement Series, 2016)
Most of the celestial γ rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20°and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within ∼4°of the Galactic Center.
Keywords: gamma rays: diffuse background; gamma rays: general; gamma rays: ISM

Diamond formation kinetics in shock-compressed C─H─O samples recorded by small-angle x-ray scattering and x-ray diffraction - He, Zhiyu; Rödel, Melanie; Lütgert, Julian; Bergermann, Armin; Bethkenhagen, Mandy; Chekrygina, Deniza; Cowan, Thomas E.; Descamps, Adrien; French, Martin; Galtier, Eric; Gleason, Arianna E.; Glenn, Griffin D.; et al. (Science Advances, 2022)
Extreme conditions inside ice giants such as Uranus and Neptune can result in peculiar chemistry and structural transitions, e.g., the precipitation of diamonds or superionic water, as so far experimentally observed only for pure C─H and H2O systems, respectively. Here, we investigate a stoichiometric mixture of C and H2O by shock-compressing polyethylene terephthalate (PET) plastics and performing in situ x-ray probing. We observe diamond formation at pressures between 72 ± 7 and 125 ± 13 GPa at temperatures ranging from 3500 to 6000 K. Combining x-ray diffraction and small-angle x-ray scattering, we access the kinetics of this exotic reaction. The observed demixing of C and H2O suggests that diamond precipitation inside the ice giants is enhanced by oxygen, which can lead to isolated water and thus the formation of superionic structures relevant to the planets' magnetic fields. Moreover, our measurements indicate a way of producing nanodiamonds by simple laser-driven shock compression of cheap PET plastics.
CRIS-Team Scopus Importer:2022-09-16

Dichte im Physikunterricht: Pilotierung einer deutschen Version des Density Survey - Zenger, Tim; Bitzenbauer, Philipp (Unsicherheit als Element von naturwissenschaftsbezogenen Bildungsprozessen Gesellschaft für Didaktik der Chemie und Physik Jahrestagung 2021, 2022)

Die Universität als Keimzelle und Betreiber des ESFZ - Fösel, Angela; Anton, Gisela (Best Practices und Tipps von Expert:innen für Schülerforschungszentren. Rahmenbedingungen. Kooperationen. Qualitätskriterien., 2020)
Keywords: Erlanger SchülerforschungsZentrum; ESFZ

Differential cross sections for neutron-proton scattering in the region of the d* (2380) dibaryon resonance - Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F. S.; Berlowski, M.; Bhatt, H.; Buescher, M.; Calen, H.; Ciepal,; Clement, H.; Coderre, D.; et al. (Physical Review C - Nuclear Physics, 2020)
Differential cross sections have been extracted from exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over barp scattering performed in the energy region of the d* (2380) dibaryon resonance covering the range of beam energies T-n = 0.98-1.29 GeV (root s = 2.32-2.44 GeV). The experiment was carried out with the WASA-at-COSY setup having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process dp -> np + p(spectator). In this way the np differential cross section sigma (Theta) was measured over a large angular range. The obtained angular distributions complement the corresponding analyzing power A(y)(Theta) measurements published previously. A SAID partial-wave analysis incorporating the new data strengthens the finding of a resonance pole in the coupled D-3(3) - (3)G(3) waves.
CRIS-Team WoS Importer:2020-07-31

Diffuse Galactic gamma-ray emission with H.E.S.S. - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E. O.; Backes, Michael; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; et al. (Physical Review D - Particles, Fields, Gravitation and Cosmology, 2014)
Diffuse γ-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse γ-ray emission at TeV energies remain sparse. After completion of the systematic survey of the inner Galaxy, the H.E.S.S. experiment is in a prime position to observe large-scale diffuse emission at TeV energies. Data of the H.E.S.S. Galactic Plane Survey are investigated in regions off known γ-ray sources. Corresponding γ-ray flux measurements were made over an extensive grid of celestial locations. Longitudinal and latitudinal profiles of the observed γ-ray fluxes show characteristic excess emission not attributable to known γ-ray sources. For the first time large-scale γ-ray emission along the Galactic plane using imaging atmospheric Cherenkov telescopes has been observed. While the background subtraction technique limits the ability to recover modest variation on the scale of the H.E.S.S. field of view or larger, which is characteristic of the inverse Compton scatter-induced Galactic diffuse emission, contributions of neutral pion decay as well as emission from unresolved γ-ray sources can be recovered in the observed signal to a large fraction. Calculations show that the minimum γ-ray emission from π0 decay represents a significant contribution to the total signal. This detection is interpreted as a mix of diffuse Galactic γ-ray emission and unresolved sources.

Discovery and follow-up studies of the extended, off-plane, VHE gamma-ray source HESS J1507-622 - Acero, Fabio; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Bernloehr, K.; Bochow, A.; Boisson, C.; Bolmont, Julien; et al. (Astronomy & Astrophysics, 2010)
Context. The detection of gamma-rays in the very-high-energy (VHE) range (100 GeV-100 TeV) offers the possibility of studying the parent population of ultrarelativistic particles found in astrophysical sources, so it is useful for understanding the underlying astrophysical processes in nonthermal sources. Aims. The discovery of the VHE gamma-ray source HESS J1507-622 is reported and possibilities regarding its nature are investigated. Methods. The H.E.S.S. array of imaging atmospheric Cherenkov telescopes (IACTs) has a high sensitivity compared with previous instruments (∼1% of the Crab flux in 25 h observation time for a 5σ point-source detection) and has a large field of view (∼5° in diameter). HESS J1507-622 was discovered within the ongoing H.E.S.S. survey of the inner Galaxy, and the source was also studied by means of dedicated multiwavelength observations. Results. A Galactic gamma-ray source, HESS J1507-622, located ∼3.5° from the Galactic plane was detected with a statistical significance >9σ. Its energy spectrum is well fitted by a power law with spectral index Γ = 2.24 ± 0.16 ± 0.20 and a flux above 1 TeV of (1.5 ± 0.4 ± 0.3) × 10 cm s. Possible interpretations (considering both hadronic and leptonic models) of the VHE gamma-ray emission are discussed in the absence of an obvious counterpart. © ESO 2010.
Keywords: gamma rays: general; X-rays: general

Discovery of an X-ray nebula around PSR J1718-3825 and implications for the nature of the gamma-ray source HESS J1718-385 - Funk, Stefan; et al. (Astronomy & Astrophysics, 2007)
Combined X-ray synchrotron and inverse-Compton gamma-ray observations of pulsar wind nebulae (PWN) may help to elucidate the processes of acceleration and energy loss in these systems. In particular, such observations provide constraints on the particle injection history and the magnetic field strength in these objects. The newly discovered TeV gamma-ray source HESS J1718-385 has been proposed as the likely PWN of the high spin-down luminosity pulsar PSR J1718-3825. The absence of previous, sensitive X-ray measurements of this pulsar, and the unusual energy spectrum of the TeV source, motivated observations of this region with XMM-Newton. The data obtained reveal a hard-spectrum X-ray source at the position of PSR 1718-3825 and evidence of diffuse emission in the vicinity of the pulsar. We derive limits on the keV emission from the centroid of HESS J1718-385 and discuss the implications of these findings for the PWN nature of this object.
CRIS-Team WoS Importer:2020-01-15

Discovery of a point-like very-high-energy γ-ray source in Monoceros - Funk, Stefan; van Eldik, Christopher; et al. (Astronomy & Astrophysics, 2007)
Aims. The complex Monoceros Loop SNR/Rosette Nebula region contains several potential sources of very-high-energy (VHE) y-ray emission and two as yet unidentified high-energy EGRET sources. Sensitive VHE observations are required to probe acceleration processes in this region. Methods. The HESS telescope array has been used to search for very high-energy y-ray sources in this region. CO data from the NANTEN telescope were used to map the molecular clouds in the region, which could act as target material for γ-ray production via hadronic interactions. Results. We announce the discovery of a new y-ray source, HESS J0632+057, located close to the rim of the Monoceros SNR. This source is unresolved by HESS and has no clear counterpart at other wavelengths but is possibly associated with the weak X-ray source 1RXS J063258.3+054857, the Be-star MWC 148 and/or the lower energy γ-ray source 3EGJ0634+0521. No evidence for an associated molecular cloud was found in the CO data. © ESO 2007.
Keywords: Gamma rays: observations

Discovery of a VHE gamma-ray source coincident with the supernova remnant CTB 37A - van Eldik, Christopher; Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, W.; Bernloehr, K.; Boisson, C.; Borrel, V.; Braun, Isabel; et al. (Astronomy & Astrophysics, 2008)
Aims. The supernova remnant (SNR) complex CTB 37 is an interesting candidate for observations with very high energy (VHE) γ-ray telescopes such as HESS. In this region, three SNRs are seen. One of them is potentially associated with several molecular clouds, a circumstance that can be used to probe the acceleration of hadronic cosmic rays. Methods. This region was observed with the HESS Cherenkov telescopes and the data were analyzed with standard HESS procedures. Recent X-ray observations with Chandra and XMM-Newton were used to search for X-ray counterparts. Results. The discovery of a new VHE γ-ray source HESS J1714-385 coincident with the remnant CTB 37A is reported. The energy spectrum is well described by a power-law with a photon index of Γ = 2.30 ± 0.13 and a differential flux at 1 TeV of Φ = (8.7 ± 1.0 ± 1.8) × 10 cm s TeV. The integrated flux above 1 TeV is equivalent to 3% of the flux of the Crab nebula above the same energy. This VHE γ-ray source is a counterpart candidate for the unidentified EGRET source 3EG J1714-3857. The observed VHE emission is consistent with the molecular gas distribution around CTB 37A; a close match is expected in a hadronic scenario for γ-ray production. The X-ray observations reveal the presence of thermal X-rays from the NE part of the SNR. In the NW part of the remnant, an extended non-thermal X-ray source, CXOU J171419.8-383023, is discovered as well. Possible connections of the X-ray emission to the newly found VHE source are discussed. © ESO 2008.
Keywords: Gamma rays: observations; ISM: supernova remnants; X-rays: individuals: G348.5+0.1

Discovery of extended VHE gamma-ray emission from the asymmetric pulsar wind nebula in MSH 15-52 with HESS - Funk, Stefan; et al. (Astronomy & Astrophysics, 2005)
The Supernova Remnant MSH 15-52 has been observed in very high energy (VHE) gamma-rays using the HESS 4-telescope array located in Namibia. A gamma-ray signal is detected at the 25 sigma level during an exposure of 22.1 h live time. The image reveals an elliptically shaped emission region around the pulsar PSRB1509 - 58, with semi-major axis similar to 6' in the NW-SE direction and semi-minor axis similar to 2'. This morphology coincides with the diffuse pulsar wind nebula as observed at X-ray energies by ROSAT. The overall energy spectrum from 280 GeV up to 40 TeV can be fitted by a power law with photon index Gamma = 2.27 +/- 0.03(stat) +/- 0.20(syst). The detected emission can be plausibly explained by inverse Compton scattering of accelerated relativistic electrons with soft photons.
CRIS-Team WoS Importer:2020-01-15

Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N 157B with H.E.S.S. - Abramowski, A.; Acero, Fabio; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balenderan, S.; Balzer, Arnim; Barnacka, A.; Becherini, Y.; Becker, J.; Bernloehr, K.; Birsin, E.; et al. (Astronomy & Astrophysics, 2012)
We present the significant detection of the first extragalactic pulsar wind nebula (PWN) detected in gamma rays, N- 157B, located in the large Magellanic Cloud (LMC). Pulsars with high spin-down luminosity are found to power energised nebulae that emit gamma rays up to energies of several tens of TeV. N- 157B is associated with PSR- J0537-6910, which is the pulsar with the highest known spin-down luminosity. The High Energy Stereoscopic System telescope array observed this nebula on a yearly basis from 2004 to 2009 with a dead-time corrected exposure of 46- h. The gamma-ray spectrum between 600- GeV and 12- TeV is well-described by a pure power-law with a photon index of 2.8 ± 0.2 ± 0.3 and a normalisation at 1- TeV of (8.2 ± 0.8 ± 2.5 ) × 10 cm - s - TeV . A leptonic multi-wavelength model shows that an energy of about 4 × 10 erg is stored in electrons and positrons. The apparent efficiency, which is the ratio of the TeV gamma-ray luminosity to the pulsar's spin-down luminosity, 0.08% ± 0.01%, is comparable to those of PWNe found in the Milky Way. The detection of a PWN at such a large distance is possible due to the pulsar's favourable spin-down luminosity and a bright infrared photon-field serving as an inverse-Compton-scattering target for accelerated leptons. By applying a calorimetric technique to these observations, the pulsar's birth period is estimated to be shorter than 10 ms. © ESO, 201
Keywords: Gamma rays: general; ISM: supernova remnants; Magellanic Clouds; Pulsars: individual: PSR J0537-6910

Discovery of gamma-ray emission from the shell-type supernova remnant RCW 86 with Hess - Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, W.; Bernloehr, K.; Boisson, C.; Bochow, A.; Borrel, V.; Braun, Isabel V; et al. (Astrophysical Journal, 2009)
The shell-type supernova remnant (SNR) RCW 86, possibly associated with the historical supernova SN 185, with its relatively large size (about 40′ in diameter) and the presence of nonthermal X-rays is a promising target for γ-ray observations. The high sensitivity, good angular resolution of a few arcminutes and the large field of view of the High Energy Stereoscopic System (HESS) make it ideally suited for the study of γ-ray morphology of such extended sources. HESS observations have indeed led to the discovery of the SNR RCW 86 in very high energy (VHE; E > 100 GeV) γ-rays. With 31 hr of observation time, the source is detected with a statistical significance of 8.5σ and is significantly more extended than the HESS point-spread function. Morphological studies have been performed and show that the γ-ray flux does not correlate perfectly with the X-ray emission. The flux from the remnant is ∼10% of the flux from the Crab nebula, with a similar photon index of about 2.5. Possible origins of the VHE γ-ray emission, via either Inverse Compton scattering by electrons or the decay of neutral pions produced by proton interactions, are discussed on the basis of spectral features obtained both in the X-ray and γ-ray regimes. © 2009. The American Astronomical Society. All rights reserved.
Keywords: gamma rays: observations; ISM: individual (RCW 86; G315.4-2.3); supernova remnants

Discovery of Gamma Rays from the Quiescent Sun with HAWC - Albert, A.; Alfaro, R.; Alvarez, C.; Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.; Babu, R.; Belmont-Moreno, E.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; Carramiñana, A.; et al. (Physical Review Letters, 2023)
We report the first detection of a TeV γ-ray flux from the solar disk (6.3σ), based on 6.1 years of data from the High Altitude Water Cherenkov (HAWC) observatory. The 0.5-2.6 TeV spectrum is well fit by a power law, dN/dE=A(E/1 TeV)-γ, with A=(1.6±0.3)×10-12 TeV-1 cm-2 s-1 and γ=3.62±0.14. The flux shows a strong indication of anticorrelation with solar activity. These results extend the bright, hard GeV emission from the disk observed with Fermi-LAT, seemingly due to hadronic Galactic cosmic rays showering on nuclei in the solar atmosphere. However, current theoretical models are unable to explain the details of how solar magnetic fields shape these interactions. HAWC's TeV detection thus deepens the mysteries of the solar-disk emission.
CRIS-Team Scopus Importer:2023-08-25

Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406 - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Astronomy and Astrophysics, 2013)
Keywords: BL Lacertae objects: individual: SHBL J001355.9-185406; gamma rays: general

Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift - Abramowski, A.; Acero, F.; Akhperjanian, A. G.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Behera, B.; Bernloehr, K.; Birsin, E.; et al. (Astronomy & Astrophysics, 2013)
Very high-energy γ-ray emission from PKS 0447-439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has a hard spectrum in the MeV to GeV range. In the TeV range, a photon index of 3.89 ± 0.37 (stat) ±0.22 (sys) and a flux normalisation at 1 TeV, Φ = (3.5 ± 1.1(stat) ± 0.9(sys)) × 10 cm s TeV were found. The detection with H.E.S.S. triggered observations in the X-ray band with the Swift and RXTE telescopes. Simultaneous UV and optical data from Swift UVOT and data from the optical telescopes ATOM and ROTSE are also available. The spectrum and light curve measured with H.E.S.S. are presented and compared to the multi-wavelength data at lower energies. A rapid flare is seen in the Swift XRT and RXTE data, together with a flux variation in the UV band, at a time scale of the order of one day. A firm upper limit of z < 0.59 on the redshift of PKS 0447-439 is derived from the combined Fermi-LAT and H.E.S.S. data, given the assumptions that there is no upturn in the intrinsic spectrum above the Fermi-LAT energy range and that absorption on the extragalactic background light (EBL) is not weaker than the lower limit provided by current models. The spectral energy distribution is well described by a simple one-zone synchrotron self-Compton scenario, if the redshift of the source is less than z â‰ 0.4. © 2013 ESO.
Keywords: BL Lacertae objects: individual: PKS 0447-439; Galaxies: active; Gamma rays: galaxies; Radiation mechanisms: non-thermal

Discovery of the binary pulsar PSRB1259-63 in very-high-energy gamma rays around periastron with HESS - Funk, Stefan; et al. (Astronomy & Astrophysics, 2005)
We report the discovery of very-high-energy (VHE) gamma-ray emission of the binary system PSRB1259-63/SS2883 of a radio pulsar orbiting a massive, luminous Be star in a highly eccentric orbit. The observations around the 2004 periastron passage of the pulsar were performed with the four 13 m Cherenkov telescopes of the HESS experiment, recently installed in Namibia and in full operation since December 2003. Between February and June 2004, a gamma-ray signal from the binary system was detected with a total significance above 13 sigma. The flux was found to vary significantly on timescales of days which makes PSRB1259- 63 the first variable galactic source of VHE gamma-rays observed so far. Strong emission signals were observed in pre- and post-periastron phases with a flux minimum around periastron, followed by a gradual flux decrease in the months after. The measured time-averaged energy spectrum above a mean threshold energy of 380 GeV can be fitted by a simple power law F-0(E/1TeV)(-Gamma) with a photon index Gamma = 2.7 +/- 0.2(stat) +/- 0.2(sys) and flux normalisation F-0 = ( 1.3 +/- 0.1stat +/- 0.3(sys)) x 10(-12) TeV-1 cm(-2) s(-1). This detection of VHE gamma-rays provides unambiguous evidence for particle acceleration to multi-TeV energies in the binary system. In combination with coeval observations of the X-ray synchrotron emission by the RXTE and INTEGRAL instruments, and assuming the VHE gamma-ray emission to be produced by the inverse Compton mechanism, the magnetic field strength can be directly estimated to be of the order of 1G.
CRIS-Team WoS Importer:2020-01-15

Discovery of the Hard Spectrum VHE γ-Ray Source HESS J1641-463 - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Uner, E. O. Ang; Backes, Michael; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; et al. (Astrophysical Journal Letters, 2014)
Keywords: cosmic rays; gamma rays: general; ISM: individual objects (SNR G338.30.0; SNR G338.5+0.1)

Discovery of the source HESS J1356-645 associated with the young and energetic PSR J1357-6429 - van Eldik, Christopher; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; De Almeida, U. Barres; Becherini, Y.; Becker, J.; Behera, B.; et al. (Astronomy & Astrophysics, 2011)
Context. Several newly discovered very-high-energy (VHE; E > 100 GeV) γ-ray sources in the Galaxy are thought to be associated with energetic pulsars. Among them, middle-aged (10 yr) systems exhibit large centre-filled VHE nebulae, offset from the pulsar position, which result from the complex relationship between the pulsar wind and the surrounding medium, and reflect the past evolution of the pulsar. Aims. Imaging Atmospheric Cherenkov Telescopes (IACTs) have been successful in revealing extended emission from these sources in the VHE regime. Together with radio and X-ray observations, this observational window allows one to probe the energetics and magnetic field inside these large-scale nebulae. Methods. H.E.S.S., with its large field of view, angular resolution of 0.1° and unprecedented sensitivity, has been used to discover a large population of such VHE sources. In this paper, the H.E.S.S. data from the continuation of the Galactic Plane Survey (-80° < < 60°, |b| < 3°), together with the existing multi-wavelength observations, are used. Results. A new VHE γ-ray source was discovered at RA (J2000) = 135600, Dec (J2000) =-64°30′00′′ with a 2′ statistical error in each coordinate, namely HESS J1356-645. The source is extended, with an intrinsic Gaussian width of (0.20 ± 0.02)°. Its integrated energy flux between 1 and 10 TeV of 8 × 10 erg cm s represents ∼11% of the Crab Nebula flux in the same energy band. The energy spectrum between 1 and 20 TeV is well described by a power law dN/dE E with photon index Γ = 2.2 ± 0.2 ± 0.2. The inspection of archival radio images at three frequencies and the analysis of X-ray data from ROSAT/PSPC and XMM-Newton/MOS reveal the presence of faint non-thermal diffuse emission coincident with HESS J1356-645. Conclusions. HESS J1356-645 is most likely associated with the young and energetic pulsar PSR J1357-6429 (d = 2.4 kpc, τ = 7.3 kyr and Å-= 3.1 × 10 erg s), located at a projected distance of ∼5 pc from the centroid of the VHE emission. HESS J1356-645 and its radio and X-ray counterparts would thus represent the nebula resulting from the past history of the PSR J1357-6429 wind. In a simple one-zone model, © 2011 ESO.
Keywords: gamma rays: general; ISM: individual objects: HESS J1356-645; ISM: individual objects: PSR J1357-6429; surveys

Discovery of the two "wings" of the Kookaburra complex in VHE γ-rays with HESS - Funk, Stefan; van Eldik, Christopher; et al. (Astronomy & Astrophysics, 2006)
Aims. Search for Very High Energy γ-ray emission in the Kookaburra complex through observations with the HESS array. Methods. Stereoscopic imaging of Cherenkov light emission of the γ-ray showers in the atmosphere is used for the reconstruction and selection of the events to search for γ-ray signals. Their spectrum is derived by a forward-folding maximum likelihood fit. Results. Two extended γ-ray sources with an angular (68%) radius of 3.3-3.4′ are discovered at high (>13σ) statistical significance: HESS J1420-607 and HESS J1418-609. They exhibit a flux above 1 TeV of (2.97 ±0.188 ±0.60) × 10 and (2.17 ±0.17 ±0.43) × 10 cm s, respectively, and similar hard photon indices ∼2.2. Multi-wavelength comparisons show spatial coincidence with the wings of the Kookaburra. Two pulsar wind nebulae candidates, K3/PSR J1420-6048 and the Rabbit, lie on the edge of the HESS sources. Conclusions. The two new sources confirm the non-thermal nature of at least parts of the two radio wings which overlap with the γ-ray emission and establish their connection with the two X-ray pulsar wind nebulae candidates. Given the large point spread function of EGRET, the unidentified source(s) 3EG J1420-6038/GeV J1417-6100 could possibly be related to either or both HESS sources. The most likely explanation for the Very High Energy γ-rays discovered by HESS is inverse Compton emission of accelerated electrons on the Cosmic Microwave Background near the two candidate pulsar wind nebulæ, K3/PSR J1420-6048 and the Rabbit. Two scenarios which could lead to the observed large (∼10 pc) offset-nebula type morphologies are briefly discussed. © ESO 2006.
Keywords: Gamma rays: observations; ISM: general; Radiation mechanisms: non-thermal

Discovery of the VHE gamma-ray source HESS J1832-093 in the vicinity of SNR G22.7-0.2 - Abramowski, A.; Acero, F.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguner, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; et al. (Monthly Notices of the Royal Astronomical Society, 2015)
Keywords: astroparticle physics; ISM: individual objects: HESS J1832-093; ISM: individual objects: SNR G22.7-0.2; gamma-rays: general

Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856 - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E. O.; Backes, Michael; Balzer, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; Bernhard, S.; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2015)
Re-observations with the HESS telescope array of the very high-energy (VHE) source HESS J1018-589A that is coincident with the Fermi-LAT gamma-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9 sigma and the detection of variability (chi(2)/nu of 238.3/155) in the emitted gamma-ray flux. This variability confirms the association of HESS J1018-589A with the high-energy gamma-ray binary detected Fermi-LAT and also confirms the point-like source as a new VHE binary system. The spectrum of HESS J1018-589A is best fit with a power-law function with photon index Gamma = 2.20 +/- 0.14(stat) +/- 0.2(sys). Emission is detected up to similar to 20 TeV. The mean differential flux level is (2.9 +/- 0.4) x 10(-13) TeV-1 cm(-2) s(-1) at 1 TeV, equivalent to similar to 1% of the flux from the Crab Nebula at the same energy. Variability is clearly detected the night-by-night light curve. When folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed X-ray high-energy phaseograms. The fit of the HESS phaseogram to a constant flux provides evidence of periodicity at the level of N-sigma > 3 sigma. The of the VHE phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with a modest impact from VHE gamma-ray due to pair production (tau less than or similar to 1 at 300 GeV).
Keywords: Acceleration of particles; Gamma rays: stars; Radiation mechanisms: non-thermal; Stars: individual: 1FGL J1018.6-5856; X-rays: binaries

Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W 28 (G6.4-0.1) field - Aharonian, F.; Akhperjanian, A. G.; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, Wystan; Berge, David; Bernloehr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, Isabel V; et al. (Astronomy & Astrophysics, 2008)
Aims. Observations of shell-type supernova remnants (SNRs) in the GeV to multi-TeV -ray band, coupled with those at millimetre radio wavelengths, are motivated by the search for cosmic-ray accelerators in our Galaxy. The old-age mixed-morphology SNR W 28 (distance ∼2 kpc) is a prime target due to its interaction with molecular clouds along its northeastern boundary and other clouds situated nearby.Methods. We observed the W 28 field (for ∼40 h) at very high energy (VHE) -ray energies ( 0.1]]> TeV) with the HESS. Cherenkov telescopes. A reanalysis of EGRET 100]]> MeV data was also undertaken. Results from the NANTEN 4 m telescope Galactic plane survey and other CO observations were used to study molecular clouds. Results. We have discovered VHE -ray emission (HESS J1801-233) coincident with the northeastern boundary of W 28 and a complex of sources (HESS J1800-240A, B and C) ∼0.5° south of W 28 in the Galactic disc. The EGRET source (GRO J1801-2320) is centred on HESS J1801-233 but may also be related to HESS J1800-240 given the large EGRET point spread function. The VHE differential photon spectra are well fit by pure power laws with indices ∼2.3 to 2.7. The spectral indices of HESS J1800-240A, B, and C are consistent within statistical errors. All VHE sources are ∼10 in intrinsic radius except for HESS J1800-240C, which appears pointlike. The NANTEN CO() data reveal molecular clouds positionally associating with the VHE emission, spanning a ∼15 km s range in local standard of rest velocity. Conclusions. The VHE/molecular cloud association could indicate a hadronic origin for HESS J1801-233 and HESS J1800-240, and several cloud components in projection may contribute to the VHE emission. The clouds have components covering a broad velocity range encompassing the distance estimates for W 28 (∼2 kpc) and extending up to ∼4 kpc. Assuming hadronic origin and distances of 2 and 4 kpc for cloud components, the required cosmic-ray density enhancement factors (with respect to the solar value) are in the range ∼10 to ∼30. If situated at 2 kpc distance, such cosmic-ray densities may be supplied by SNRs like W 28. Additionally and/or alternatively, particle acceleration may come from several catalogued SNRs and SNR candidates, the energetic ultra compact HII region W 28A2, and the HII regions M 8 and M 20, along with their associated open clusters. Further sub-mm observations would be recommended to probe in detail the dynamics of the molecular clouds at velocites ]]> 10 km s and their possible connection to W 28. © 2008 ESO.
Keywords: Gamma rays: observations

Discovery of very high energy gamma rays associated with an X-ray binary - Funk, Stefan; et al. (Science, 2005)
X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and x-ray observations have led to the presumption that some x-ray binaries called microquasars behave as scaled-down active galactic nuclei. Microquasars have resolved radio emission that is thought to arise from a relativistic outflow akin to active galactic nuclei jets, in which particles can be accelerated to large energies. Very high energy gamma-rays produced by the interactions of these particles have been observed from several active galactic nuclei. Using the High Energy Stereoscopic System, we find evidence for gamma-ray emission of >100 gigaelectron volts from a candidate microquasar, LS 5039, showing that particles are also accelerated to very high energies in these systems.
CRIS-Team WoS Importer:2020-01-15

Discovery of very high energy γ-ray emission from centaurus a with H.E.S.S. - Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Benbow, W.; Bernloehr, K.; Boisson, C.; Bochow, A.; Borrel, V.; et al. (Astrophysical Journal, 2009)
We report the discovery of faint very high energy (VHE; E > 100GeV) γ-ray emission from the radio galaxy Centaurus A in observations performed with the High Energy Stereoscopic System (H.E.S.S.) experiment, an imaging atmospheric Cherenkov telescope array consisting of four telescopes located in Namibia. Centaurus A has been observed for more than 120hr. A signal with a statistical significance of 5.0σ is detected from the region including the radio core and the inner kpc jets. The integral flux above an energy threshold of 250 GeV is measured to be 0.8% of the flux of the Crab Nebula (apparent luminosity: L(>250GeV) 2.6 × 10ergs, adopting a distance of 3.8Mpc). The spectrum can be described by a power law with a photon index of 2.7 0.5 0.2. No significant flux variability is detected in the data set. However, the low flux only allows detection of variability on the timescale of days to flux increments above a factor of 15-20 (3σ and 4σ, respectively). The discovery of VHE γ-ray emission from Centaurus A reveals particle acceleration in the source to >TeV energies and, together with M87, establishes radio galaxies as a class of VHE emitters. © 2009. The American Astronomical Society. All rights reserved..
Keywords: Galaxies: active; Galaxies: individual (Cen A); Gamma rays: observations

(untitled) - van Eldik, Christopher; et al.
The extreme synchrotron BL Lac object H 2356-309, located at a redshift of z = 0.165, was observed from June to December 2004 with a total exposure of ≈40 h live-time with the HESS (High Energy Stereoscopic System) array of atmospheric-Cherenkov telescopes (ACTs). Analysis of this data set yields, for the first time, a strong excess of 453 γ-rays (10 standard deviations above background) from H 2356-309, corresponding to an observed integral flux above 200 GeV of I(>200 GeV) = (4.1 ±0.5) × 10 cm s (statistical error only). The differential energy spectrum of the source between 200 GeV and 1.3TeV is well-described by a power law with a normalisation (at 1 TeV) of N = (3.00 ±0.80 ± 0.31 )× 10 cm s TeV and a photon index of γ = 3.09 ± 0.24 ± 0.10 . H 2356-309 is one of the most distant BL Lac objects detected at very-high-energy γ-rays so far. Results from simultaneous observations from ROTSE-III (optical), RXTE (X-rays) and NRT (radio) are also included and used together with the HESS data to constrain a single-zone homogeneous synchrotron self-Compton (SSC) model. This model provides an adequate fit to the HESS data when using a reasonable set of model parameters. © ESO 200

Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301-243 with H.E.S.S. - Abramowski, A.; Acero, F.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; et al. (Astronomy & Astrophysics, 2013)
The active galactic nucleus PKS 0301-243 (z = 0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV <e 0301-243="" 100="" at="" by="" discovery="" e="" energies="" fermi="" high="" lat.="" of="" on="" paper="" pks="" reports="" the="" this="" very=""> 100 GeV) by the High Energy Stereoscopic System (H.E.S.S.) from observations between September 2009 and December 2011 for a total live time of 34.9 h. Gamma rays above 200 GeV are detected at a significance of 9.4σ. A hint of variability at the 2.5σ level is found. An integral flux I(E > 200 GeV) = (3.3 ± 1.1 ± 0.7) × 10 ph cm s and a photon index Γ = 4.6 ± 0.7 ± 0.2 are measured. Multi-wavelength light curves in HE, X-ray and optical bands show strong variability, and a minimal variability timescale of eight days is estimated from the optical light curve. A single-zone leptonic synchrotron self-Compton scenario satisfactorily reproduces the multi-wavelength data. In this model, the emitting region is out of equipartition and the jet is particle dominated. Because of its high redshift compared to other sources observed at TeV energies, the very high energy emission from PKS 0301-243 is attenuated by the extragalactic background light (EBL) and the measured spectrum is used to derive an upper limit on the opacity of the EBL. © 2013 ESO.</e>
Keywords: BL Lacertae objects: general; BL Lacertae objects: individual: PKS 0301-243; Galaxies: active; Gamma rays: galaxies; Radiation mechanisms: non-thermal

Discovery of very-high-energy γ-rays from the Galactic Centre ridge - van Eldik, Christopher; et al. (Nature, 2006)
The source of Galactic cosmic rays (with energies up to 10 eV) remains unclear, although it is widely believed that they originate in the shock waves of expanding supernova remnants. At present the best way to investigate their acceleration and propagation is by observing the γ-rays produced when cosmic rays interact with interstellar gas . Here we report observations of an extended region of very-high-energy (>10 eV) γ-ray emission correlated spatially with a complex of giant molecular clouds in the central 200 parsecs of the Milky Way. The hardness of the γ-ray spectrum and the conditions in those molecular clouds indicate that the cosmic rays giving rise to the γ-rays are likely to be protons and nuclei rather than electrons. The energy associated with the cosmic rays could have come from a single supernova explosion around 10 years ago. © 2006 Nature Publishing Group.

Discovery of VHE γ-ray emission and multi-wavelength observations of the BL Lacertae object 1RXS J101015.9-311909 - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; Becherini, Y.; Becker, J.; Bernloehr, K.; Birsin, E.; Biteau, J.; et al. (Astronomy & Astrophysics, 2012)
Keywords: gamma rays: galaxies; galaxies: active; BL Lacertae objects: individual: 1RXS J101015.9-311909

Discovery of VHE γ-rays from the high-frequency-peaked BL Lacertae object RGB J0152+017 - Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, W.; Bernloehr, K.; Boisson, C.; Borrel, V.; Braun, Isabel V; Brion, E.; et al. (Astronomy & Astrophysics, 2008)
Keywords: galaxies: BL Lacertae objects: individual: RGB J0152+017; gamma rays: observations; galaxies: BL Lacertae objects: general; galaxies: active

Discovery of VHE emission towards the Carina arm region with the H.E.S.S. telescope array: HESS? J1018-589 - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; Becherini, Y.; Becker, J.; Bernloehr, K.; Birsin, E.; Biteau, J.; et al. (Astronomy & Astrophysics, 2012)
The Carina arm region, containing the supernova remnant SNR? G284.3-1.8, the high-energy (HE; E > 100 MeV) binary 1FGL? J1018.6-5856 and the energetic pulsar PSR? J1016-5857 and its nebula, has been observed with the H.E.S.S. telescope array. The observational coverage of the region in very-high-energy (VHE; E > 0.1? TeV) γ-rays benefits from deep exposure (40? h) of the neighboring open cluster Westerlund 2. The observations have revealed a new extended region of VHE γ-ray emission. The new VHE source HESS? J1018-589 shows a bright, point-like emission region positionally coincident with SNR? G284.3-1.8 and 1FGL? J1018.6-5856 and a diffuse extension towards the direction of PSR? J1016-5857. A soft (Γ = 2.7 ± 0.5) photon? index, with a differential flux at 1? TeV of N = (4.2 ± 1.1) × 10? TeV? cm? s is found for the point-like source, whereas the total emission region including the diffuse emission region is well fit by a power-law function with spectral index Γ = 2.9 ± 0.4 and differential flux at 1? TeV of N = (6.8 ± 1.6) × 10? TeV? cm? s. This H.E.S.S. detection motivated follow-up X-ray observations with the XMM-Newton satellite to investigate the origin of the VHE emission. The analysis of the XMM-Newton data resulted in the discovery of a bright, non-thermal point-like source (XMMU J101855.4-58564) with a photon index of Γ = 1.65 ± 0.08 in the center of SNR? G284.3-1.8, and a thermal, extended emission region coincident with its bright northern filament. The characteristics of this thermal emission are used to estimate the plasma density in the region as n 0.5 cm (2.9? kpc/d). The position of XMMU? J101855.4-58564 is compatible with the position reported by the Fermi-LAT collaboration for the binary system 1FGL? J1018.6-5856 and the variable Swift XRT source identified with it. The new X-ray data are used alongside archival multi-wavelength data to investigate the relationship between the VHE γ-ray emission from HESS? J1018-589 and the various potential counterparts in the Carina arm region. © ESO, 2012.
Keywords: Gamma rays: stars; ISM: individual objects: 1FGL J1018.6-5856; ISM: individual objects: PSRJ1016-5857; ISM: individual objects: SNRG284.3-1.8

Discovery of VHE gamma rays from PKS 2005-489 - Funk, Stefan; et al. (Astronomy & Astrophysics, 2005)
The high-frequency peaked BL Lac PKS 2005 2005-489 (z = 0.071) was observed in 2003 and 2004 with the HESS stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. A signal was detected at the 6.7 sigma level in the 2004 observations (24.2 h live time), but not in the 2003 data set (27.3 h live time). PKS 2005 2005-489 is the first blazar independently discovered by HESS to be an emitter of VHE photons, a independently and only the second such blazar in and the Southern Hemisphere. The integral flux above 200GeV observed in 2004 is (6.9 +/- 1.0(stat) +/- 1.4(syst)) x 10(-12) cm(-2) s(-1), corresponding to similar to 2.5% of the flux observed from the Crab Nebula. The 99% upper limit on the flux in 2003, I(> 200 GeV) < 5.2 x 10(-12) cm cm(-2) s(-1), is smaller than, the flux measured in 2004, suggesting an increased level of activity in 2004. However, the data show no evidence for significant variability on any time scale less than a year. An energy spectrum is measured and is characterized by a very soft power law (photon index of G = 4.0 +/- 0.4).
CRIS-Team WoS Importer:2020-01-15

Discovery of VHE γ -rays from the BL Lacertae object PKS 0548-322 - Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Benbow, W.; Bernloehr, K.; Bochow, A.; Boisson, C.; Bolmont, J.; et al. (Astronomy & Astrophysics, 2010)
Aims. PKS 0548-322 (z = 0.069) is a "high-frequency-peaked" BL Lac object and a candidate very high energy (VHE, E > 100 GeV) γ-ray emitter, due to its high X-ray and radio flux. Observations at the VHE band provide insights into the origin of very energetic particles present in this source and the radiation processes at work. Methods. We report observations made between October 2004 and January 2008 with the HESS array, a four imaging atmospheric-Cherenkov telescopes. Contemporaneous UV and X-ray observations with the Swift satellite in November 2006 are also reported. Results. PKS 0548-322 is detected for the first time in the VHE band with HESS We measure an excess of 216 γ-rays corresponding to a significance of 5.6 standard deviations. The photon spectrum of the source is described by a power-law, with a photon index of Γ = 2.86 ± 0.34 ± 0.10 . The integral flux above 200 GeV is ∼1.3% of the flux of the Crab Nebula, and is consistent with being constant in time. Contemporaneous Swift/XRT observations reveal an X-ray flux between 2 and 10 keV of F = (2.3±0.2)×10 erg cm s, an intermediate intensity state with respect to previous observations. The spectral energy distribution can be reproduced using a simple one-zone synchrotron self Compton model, with parameters similar those observed for other sources of this type. © 2010 ESO.
Keywords: BL Lacertae objects: individual: PKS 0548-322; galaxies: active; gamma rays: observations

Discrimination analysis of breast calcifications using x-ray dark-field radiography - Rauch, Thomas; Rieger, Jens; Pelzer, Georg; Horn, Florian; Erber, Ramona; Wunderle, Marius; Emons, Julius; Nabieva, Naiba; Fuhrich, Nicole; Michel, Thilo; Hartmann, Arndt; Fasching, Peter; et al. (Medical Physics, 2020)
Background X-ray dark-field radiography could enhance mammography by providing more information on imaged tissue and microcalcifications. The dark field signal is a measure of small angle scattering and can thus provide additional information on the imaged materials. This information can be useful for material distinction of calcifications and the diagnosis of breast cancer by classifying benign and malign association of these calcifications.
CRIS-Team WoS Importer:2020-03-06

Disordered spherical bead packs are anisotropic - Schröder-Turk, Gerd; Mickel, Walter; Schröter, Matthias; Delaney, Gary; Saadatfar, Mohammad; Senden, T.J.; Mecke, Klaus; Aste, T. (EPL - Europhysics Letters, 2010)
Investigating how tightly objects pack space is a long-standing problem, with relevance for many disciplines from discrete mathematics to the theory of glasses. Here we report on the fundamental yet so far overlooked geometric property that disordered mono-disperse spherical bead packs have significant local structural anisotropy manifest in the shape of the free space associated with each bead. Jammed disordered packings from several types of experiments and simulations reveal very similar values of the cell anisotropy, showing a linear decrease with packing fraction. Strong deviations from this trend are observed for unjammed configurations and for partially crystalline packings above 64%. These findings suggest an inherent geometrical reason why, in disordered packings, anisotropic shapes can fill space more efficiently than spheres, and have implications for packing effects in non-spherical liquid crystals, foams and structural glasses.

Distinguishing features of high altitude negative leaders as observed with LOFAR - Scholten, O.; Hare, B. M.; Dwyer, J.; Liu, N.; Sterpka, C.; Buitink, S.; Corstanje, A.; Falcke, H.; Huege, T.; Hörandel, J. R.; Krampah, G. K.; Mitra, P.; et al. (Atmospheric Research, 2021)
We present high resolution observations of negative leaders at high altitude using the LOFAR radio telescope. We show that the structure of negative leaders at high altitude (altitudes larger than 7 km) differs in several respects from that of negative leaders at lower altitudes. In particular, the High Altitude Negative Leaders (HANLs) show very distinct steps of a few hundred meters, stepping times of the order of a few milliseconds and a filamentary structure that extends outward over several hundreds of meters; as opposed to lower altitude (≲ 5 km) leaders, which have stepping times and distances around 0.01 ms and 10 m. Similar to lower altitude leaders, high altitude leaders emit copious VHF radiation from their propagating tip and have propagation velocities of the order of 105 m/s. Corona-flash like bursts can be distinguished when zooming in to meter and nanosecond scales.
CRIS-Team Scopus Importer:2021-07-02
Keywords: Corona flash; Lightning; LOFAR lightning imaging; Negative leaders; Radio emission; Thunderstorms

Drift chamber calibration and particle identification in the P-349 experiment - Alfs, D.; Asaturyan, A.; Carmignotto, M.; Diermaier, M.; Eyrich, Wolfgang; Glowacz, B.; Grzonka, D.; Hauenstein, F.; Horn, T.; Kilian, K.; Lersch, D.; Malbrunot-Ettenauer, S.; et al. (MESON 2018 – 15th International Workshop on Meson Physics, 2019)
CRIS-Team WoS Importer:2019-06-28

Dual-frequency VLBI study of Centaurus A on sub-parsec scales The highest-resolution view of an extragalactic jet - Müller, Cornelia; Kadler, Matthias; Roopesh, Ojha; Wilms, Jörn; Böck, Moritz; Edwards, P. G.; Fromm, C. M.; Hase, H.; Horiuchi, S.; Katz, Uli; Lovell, J. E. J.; Ploetz, C.; et al. (Astronomy & Astrophysics, 2011)
Context. Centaurus A is the closest active galactic nucleus. High resolution imaging using Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on sub-parsec scales, providing essential information for jet emission and formation models.Aims. Our aim is to study the structure and spectral shape of the emission from the central-parsec region of Cen A.Methods. As a target of the Southern Hemisphere VLBI monitoring program TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, and South Africa.Results. The first dual-frequency images of this source are presented along with the resulting spectral index map. An angular resolution of 0.4 mas x 0.7 mas is achieved at 8.4 GHz, corresponding to a linear scale of less than 0.013 pc. Hence, we obtain the highest resolution VLBI image of CenA, comparable to previous space-VLBI observations. By combining with the 22.3 GHz image, which has been taken without contributing transoceanic baselines at somewhat lower resolution, we present the corresponding dual-frequency spectral index distribution along the sub-parsec scale jet revealing the putative emission regions for recently detected gamma-rays from the core region by Fermi/LAT.Conclusions. We resolve the innermost structure of the milliarcsecond scale jet and counterjet system of CenA into discrete components. The simultaneous observations at two frequencies provide the highest resolved spectral index map of an AGN jet allowing us to identify multiple possible sites as the origin of the high energy emission.
Keywords: techniques: high angular resolution; galaxies: individual: Centaurus A; black hole physics; galaxies: active; galaxies: individual: NGC 5128; galaxies: jets

Dynamics of Development of Laser-Induced Structures on the Surface of a Titanium Alloy - Fomicheva, Iana; Druzhinin, Petr; Amler, Hans; Schuesslbauer, Wolfgang; Christiansen, Silke; Leuchs, Gerd (Proceedings of SPIE - The International Society for Optical Engineering, 2023)
We investigated the dynamics of LSFL (Low Spatial Frequency LIPSS) evolution on the titanium alloy surface. To create them, 12 W picosecond 1.064 μm laser with a pulse repetition rate from 50 kHz to 500 kHz was used. For different laser repetition rate (500, 150, 100 and 50 kHz), the ranges of LSFL periods and peak Fluence of pulse (Fp) for which the maximum period is reached were determined. We also determined the laser parameters at which the resulting LSFL have good quality and uniformity, regardless of the initial surface roughness.
CRIS-Team Scopus Importer:2023-06-02
Keywords: HSFL; LIPSS; LSFL; surface patterning; Ti6Al4V; titanium alloy

Dynamikerweiterung durch Weißabgleich im Bildsensor - Schöberl, Michael; Schnurrer, Wolfgang; Foessel, S.; Kaup, André (16. Farbworkshop der German Color Group, Ilmenau, 2010)
Heutige Kameras besitzen eine feste spektrale Empfindlichkeit und können bei Beleuchtung ungünstiger Farbtemperatur nur einen reduzierten Dynamikbereich aufnehmen. Diese Einschränkung kann über ein neues Verfahren deutlich reduziert werden: Über ein digitales Neutraldichtefilte(ND-Filter) wird eine selektive Reduktion der Sensorempfindlichkeit für manche Farbkanäle erreicht. Dies führt zu einer Angleichung der Farbkanäle und damit einer Erweiterung des nutzbaren Dynamikumfangs. Die Anpassungen können digital schaltbar realisiert werden bei gleichzeitigem Erhalt der Blende, Bewegungsunschärfe und Sensorempfindlichkei

Echoortung in Natur und Technik - Fösel, Angela (Naturwissenschaften im Unterricht. Physik, 2023)

Editorial. Focus on Physics Competitions 2016 - Fösel, Angela; Mathelitsch, Leopold (European Journal of Physics, 2017)

Effective LQC model for k=+1 isotropic cosmologies from spatial discretizations - Liegener, Klaus; Weigl, Stefan (Physical Review D, 2020)
The closed, spatially isotropic Friedmann-Lemaître-Robertson-Walker universe (k=+1) is endowed with modifications due to a discrete underlying space-structure. Motivated from loop quantum gravity techniques, a full Thiemann regularization is performed. The impact of these modifications of the single-graph-sector appearing in the scalar constraint are interpreted as physical quantum gravity effects. We investigate the form of the modified scalar constraint and its analytical approximations for k=+1 spacetimes and assume this effective constraint as the generator of dynamics on the reduced isotropic phase space. It transpires that the system still features a classical recollapse with only marginal discreteness corrections. Moreover, the initial and final singularities are resolved and we present an effective model mirroring the qualitative features of system.
CRIS-Team Scopus Importer:2020-12-11

Efficient Polymer Solar Cells Based on Non-fullerene Acceptors with Potential Device Lifetime Approaching 10 Years - Du, Xiaoyan; Heumüller, Thomas; Gruber, Wolfgang; Classen, Andrej; Unruh, Tobias; Li, Ning; Brabec, Christoph (Joule, 2019)
Organic solar cells (OSCs) based on non-fullerene acceptors (NFAs) have developed very fast in recent years. A proper balance among power conversion efficiency (PCE), stability, and production cost needs further elaboration. Here we investigate the industrial viability of highly efficient OSCs based on several representative NFAs. The most stable OSCs exhibit PCE of ∼8% along with extrapolated T 80 lifetime (80% of the initial PCE) of over 11,000 hr under equivalent 1 sun illumination, which would lead to a very impressive operational lifetime approaching 10 years. Photo-stability is strongly dependent on the end-group and side-chain engineering of the NFAs. Breaking of conjugation during photo-aging leads to increased energetic traps. Fluorination of the end-group stabilizes molecules against light soaking, while adding methyl groups shows an opposite trend. Side-chain modification can significantly influence the morphological stability. Reducing synthetic complexity of this class of NFAs will ultimately push the organic photovoltaics technology into real-life applications. © 2018 Elsevier Inc. We investigate the industrial viability of highly efficient organic solar cells (OSCs) based on several representative non-fullerene acceptors (NFAs) by taking into consideration the three essential parameters: power conversion efficiency, photo-stability, and materials cost. End-group and side-chain modifications of NFAs strongly influence long-term photo-stability. Promising extrapolated operational lifetime approaching 10 years has been demonstrated with the most stable system. Industrial figure of merit (i-FoM) analysis highlights the importance of lowering the synthetic complexity of the NFAs for commercialization of this technology. © 2018 Elsevier Inc. Organic solar cells with non-fullerene acceptors (NFAs) have developed rapidly in recent years. Breakthroughs in power conversion efficiency (PCE) have significantly raised the confidence in the community for commercialization of this technology. In the phase of developing new materials via molecular engineering, more attention should be paid on industrial figure of merit (i-FoM), which considers the balance of PCE, stability, and production cost. Here we investigate industrial viability of highly efficient organic solar cells based on several representative NFAs. Molecular engineering on both end-groups and side chains significantly influences the long-term stability of organic solar cells by altering the intrinsic chemical stability of the molecules under light soaking as well as morphological stability. Promising lifetime approaching 10 years is demonstrated in stable candidates. Reducing synthetic complexity is highlighted in order to push this technology into real-life appli
Keywords: non-fullerene acceptors; organic photovoltaics; device operational stability; industrial figure of merit; bulk-heterojunction morphology

Efficient propagation of systematic uncertainties from calibration to analysis with the SnowStorm method in IceCube - Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Alispach, C.; Atoum, B. Al; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, Gisela; Argüelles, C.; et al. (Journal of Cosmology and Astroparticle Physics, 2019)
Efficient treatment of systematic uncertainties that depend on a large number of nuisance parameters is a persistent difficulty in particle physics and astrophysics experiments. Where low-level effects are not amenable to simple parameterization or re-weighting, analyses often rely on discrete simulation sets to quantify the effects of nuisance parameters on key analysis observables. Such methods may become computationally untenable for analyses requiring high statistics Monte Carlo with a large number of nuisance degrees of freedom, especially in cases where these degrees of freedom parameterize the shape of a continuous distribution. In this paper we present a method for treating systematic uncertainties in a computationally efficient and comprehensive manner using a single simulation set with multiple and continuously varied nuisance parameters. This method is demonstrated for the case of the depth-dependent effective dust distribution within the IceCube Neutrino Telescope.
CRIS-Team Scopus Importer:2019-12-13
Keywords: neutrino detectors; neutrino experiments; ultra high energy photons and neutrinos

Eine kleine Geschichte der Elektroautos - Fösel, Angela (Praxis der Naturwissenschaften - Physik in der Schule, 2015)

Einführung in die Hydromechanik im fachübergreifenden Kontext - Meyn, Jan-Peter (PhyDid A, Physik und Didaktik in Schule und Hochschule [Elektronische Ressource], 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dphy.PI.PDP.einfhr

Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar - Clark, Colin J.; Pletsch, Holger J.; Wu, Jason; Guillemot, Lucas; Kerr, Matthew; Johnson, Tyrel J.; Camilo, Fernando; Salvetti, David; Allen, Bruce; Anderson, David; Aulbert, Carsten; Beer, Christian; et al. (Science Advances, 2018)
Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.
CRIS-Team WoS Importer:2020-01-15

Electromagnetic pulse protective shielding for digital x-ray detectors - Schreiner, Stephan; Rauch, Constantin; Akstaller, Bernhard; Bleuel, Paulina; Fröjdh, Eric; Martynenko, Artem S.; Mozzanica, Aldo; Neumayer, Paul; Wegert, Leonard; Zielbauer, Bernhard; Zink, Adrian; Anton, Gisela; et al. (Review of Scientific Instruments, 2023)
Laser-driven x-ray backlighting can be used to image fast dynamic processes like the propagation of laser-driven shock waves in matter. We demonstrate and evaluate the feasibility of operating the JUNGFRAU detector designed by PSI, a direct detecting x-ray detector, in environments with extreme electromagnetic pulses. The electromagnetic pulse-protective housing is specifically designed for this detector and optimized for pump-probe experiments at the Petawatt High-Energy Laser for Heavy Ion EXperiments (PHELIX) facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH. The beryllium x-ray entrance window of the protective housing has a high x-ray transmission of 94% at 8 keV. Measurements have shown that the housing simultaneously provides a relative damping of the electromagnetic field on average higher than 1000 in the frequency range of 100 MHz to 5 GHz. The results demonstrate the feasibility of operating digital detectors in experiments where strong electromagnetic pulses are present.
CRIS-Team Scopus Importer:2023-08-11

Electron acceleration in laboratory-produced turbulent collisionless shocks - Fiuza, F.; Swadling, G. F.; Grassi, A.; Rinderknecht, H. G.; Higginson, D. P.; Ryutov, D. D.; Bruulsema, C.; Drake, R. P.; Funk, Stefan; Glenzer, S.; Gregori, G.; Li, C. K.; et al. (Nature Physics, 2020)
Astrophysical collisionless shocks are among the most powerful particle accelerators in the Universe. Generated by violent interactions of supersonic plasma flows with the interstellar medium, supernova remnant shocks are observed to amplify magnetic fields(1) and accelerate electrons and protons to highly relativistic speeds(2-4). In the well-established model of diffusive shock acceleration(5), relativistic particles are accelerated by repeated shock crossings. However, this requires a separate mechanism that pre-accelerates particles to enable shock crossing. This is known as the 'injection problem', which is particularly relevant for electrons, and remains one of the most important puzzles in shock acceleration(6). In most astrophysical shocks, the details of the shock structure cannot be directly resolved, making it challenging to identify the injection mechanism. Here we report results from laser-driven plasma flow experiments, and related simulations, that probe the formation of turbulent collisionless shocks in conditions relevant to young supernova remnants. We show that electrons can be effectively accelerated in a first-order Fermi process by small-scale turbulence produced within the shock transition to relativistic non-thermal energies, helping overcome the injection problem. Our observations provide new insight into electron injection at shocks and open the way for controlled laboratory studies of the physics underlying cosmic accelerators.
CRIS-Team WoS Importer:2020-06-26

Electron spectrum of the dragonfly pulsar wind nebula from X-ray to TeV - Brisbois, Chad; Joshi, Vikas (Proceedings of Science, 2019)
The Dragonfly nebula is a Vela-like Pulsar Wind Nebula (PWN) in the Cygnus region powered by the spin down of PSR J2021+3651. In X-rays, the inner nebula is a few arcseconds across, whereas at TeV energies VERITAS and HAWC has observed extended emission much larger than the extension in X-rays. The TeV gamma-ray source HAWC J2019+368 was originally discovered in 2007 by the Milagro Observatory and has been associated with this pulsar. Recent work has shown hints of energy dependent morphology for the source at TeV energies, supporting the interpretation of the gamma-ray emission being due to Inverse Compton scattering of electrons and positrons from interstellar radiation fields and cosmic microwave background photons. The hard spectral index and spectral softening above 30 TeV of the source are consistent with Klein-Nishina suppression of the electron-photon cross-section at high energies. We will present our most recent studies in modeling and analysis of HAWC J2019+368, explaining the X-ray and TeV emission up to the highest energies using the latest data from the HAWC Observatory.
CRIS-Team Scopus Importer:2021-04-20

Empirische Forschung im Erlanger SchülerForschungsZentrum - Fösel, Angela (Naturwissenschaftlicher Unterricht und Lehrerbildung im Umbruch? Gesellschaft für Didaktik der Chemie und Physik Jahrestagung 2020, 2021)
Keywords: empirische Forschung; Erlanger SchülerForschungsZentrum; ESFZ

Empirische Forschung im Erlanger SchülerForschungsZentrum ESFZ - Erste Ergebnisse einer explorativen Fragebogenstudie - Fösel, Angela; Bitzenbauer, Philipp (PhyDid B - Didaktik der Physik - Beiträge zur DPG-Frühjahrstagung - virtuell 2021, 2021)
Seit etwas mehr als 10 Jahren gibt es das Erlanger SchülerForschungsZentrum ESFZ (https://esfz.nat.uni-erlangen.de/), verortet am Department Physik der Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg. Schülerinnen und Schüler, die Lust und Spaß am Forschen und Tüfteln an eigenen Projektideen aus dem Bereich Naturwissenschaft und Technik haben, finden hier Unterstützung in einem wissenschaftlich-professionellen Rahmen: In einwöchigen Forschungscamps nutzen bis zu 25 Jugendliche die zur Verfügung gestellte Infrastruktur, um über den Unterricht hinaus unter Betreuung von studentischen Tutor*innen und Wissenschaftler*innen an eigenen Projektideen aus Naturwissenschaft und Technik zu forschen. Im Rahmen einer explorativen Fragebogenstudie soll erhoben werden, wie Schülerinnen und Schüler, die bereits an ESFZ-Forschungscamps teilgenommen haben, die Betreuung in den Camps erlebt haben, wie sehr sie sich in das Forschungsleben eingebunden fühlten, und welche Fähigkeiten und Fertigkeiten ihrer Meinung nach in den Camps erlernt und gefördert wurden. Im Beitrag werden der für die Erhebung konzipierte Online-Fragebogen und auch die Modalitäten der Durchführung vorgestellt. Die Ergebnisse einer ersten Pilotstudie werden präsentiert, und es werden auch mögliche Forschungsfragen für daran anknüpfende Untersuchungen im Rahmen der empirischen Begleitforschung zum Erlanger SchülerForschungsZentrum diskutier
Keywords: Schülerforschungszentrum; empirische Forschung; außerschulische Lernorte

Energie - Umwelt - Gesellschaft - Hosemann, Gerhard; Finckh, Eberhard; Wirth, Eugen (Universitätsbund Erlangen, 1980)
UnivIS-Import:2017-12-18:Pub.1980.tech.IE.leen.energi

Energy dependent morphology of the pulsar wind nebula HESSJ1825-137 with Fermi-LAT - Principe, G.; Mitchell, Alison M. W.; Caroff, S.; Hinton, J. A.; Parsons, R. D.; Funk, Stefan (Astronomy & Astrophysics, 2020)
Aims. Taking advantage of more than 11 years of Fermi-LAT data, we perform a new and deep analysis of the pulsar wind nebula (PWN) HESS J1825-137. Combining this analysis with recent H.E.S.S. results we investigate and constrain the particle transport mechanisms at work inside the source as well as the system evolution. Methods. The PWN is studied using 11.6 years of Fermi-LAT data between 1 GeV and 1 TeV. In particular, we present the results of the spectral analysis and the first energy-resolved morphological study of the PWN HESS J1825-137 at GeV energies, which provide new insights into the-ray characteristics of the nebula. Results. An optimised analysis of the source returns an extended emission region larger than 2, corresponding to an intrinsic size of about 150 pc, making HESS J1825-137 the most extended-ray PWN currently known. The nebula presents a strong energy dependent morphology within the GeV range, moving from a radius of 1:4 below 10 GeV to a radius of 0.8 above 100 GeV, with a shift in the centroid location. Conclusions. Thanks to the large extension and peculiar energy-dependent morphology, it is possible to constrain the particle transport mechanisms inside the PWN HESS J1825-137. Using the variation of the source extension and position, as well as the constraints on the particle transport mechanisms, we present a scheme for the possible evolution of the system. Finally, we provide an estimate of the electron energy density and we discuss its nature in the PWN and TeV halo-like scenario.
CRIS-Team Scopus Importer:2021-04-19
Keywords: Acceleration of particles; Astroparticle physics; Gamma rays: stars; Pulsars: individual: HESS J1825-137; Pulsars: individual: PSR B1823-13

Energy dependent γ-ray morphology in the pulsar wind nebula HESS J1825-137 - Funk, Stefan; van Eldik, Christopher; et al. (Astronomy & Astrophysics, 2006)
Aims. We present results from deep γ-ray observations of the Galactic pulsar wind nebula HESS J1825-137 performed with the HESS array. Methods. Detailed morphological and spatially resolved spectral studies reveal the very high-energy (VHE) γ-ray aspects of this object with unprecedented precision. Results. We confirm previous results obtained in a survey of the Galactic Plane in 2004. The γ-ray emission extends asymmetrically to the south and south-west of the energetic pulsar PSR J1826-1334, that is thought to power the pulsar wind nebula. The differential γ-ray spectrum of the whole emission region is measured over more than two orders of magnitude, from 270 GeV to 35 TeV, and shows indications for a deviation from a pure power law. Spectra have also been determined for spatially separated regions of HESS J1825-137. The photon indices from a power-law fit in the different regions show a softening of the spectrum with increasing distance from the pulsar and therefore an energy dependent morphology. Conclusions. This is the first time that an energy dependent morphology has been detected in the VHE γ-ray regime. The VHE γ-ray emission of HESS J1825-137 is phenomenologically discussed in the scenario where the γ-rays are produced by VHE electrons via Inverse Compton scattering. The high γ-ray luminosity of the source cannot be explained on the basis of constant spin-down power of the pulsar and requires higher injection power in past. © ESO 2006.
Keywords: Gamma rays: observations; ISM: individual objects: G 18.0-0.7; ISM: individual objects: HESS J1825; ISM: individual objects: PSR B1823-13; ISM: supernova remnants; Pulsars: general

Energy spectrum of cosmic-ray electrons at TeV energies - Aharonian, F.; Akhperjanian, A. G.; Barres De Almeida, Ulisses; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Benbow, W.; Bernloehr, K.; Boisson, C.; Bochow, A.; Borrel, V.; Braun, Isabel V; et al. (Physical Review Letters, 2008)
The very large collection area of ground-based γ-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies. © 2008 The American Physical Society.

Erneuerbare Energien im Experiment - Wolfrum, Tobias; Fösel, Angela (PhyDid B - Didaktik der Physik - Beiträge zur DPG-Frühjahrstagung, 2016)
Erneuerbare Energien rücken immer mehr in den Fokus einer modernen Energiepolitik. Solar- und Windenergie beispielsweise bieten Möglichkeiten für eine regenerative, „saubere“ Energieversorgung, und deren Nutzung ist mittlerweile durch Photovoltaik- und Windenergieanlagen vielerorts präsent. Noch recht selten anzutreffen sind Häuser bzw. Einrichtungen, die schon jetzt vollends energieautark sind, vielmehr wird meist eine Einspeisung in das öffentliche Stromnetz betrieben. Auch im Physikunterricht wird eine Intensivierung der Auseinandersetzung mit der Thematik „regenerative“ Energien angestrebt. Geeignete Modellexperimente, die Technologie, Funktionsweise und Wirkungsgrad von Solarzellen und Windrädern für Schülerinnen und Schüler erfahrbar und verständlich machen, gibt es bislang nur wenige. An der Friedrich-Alexander-Universität wurde im Rahmen eines physikdidaktischen Studierendenseminars ein energieautarkes Modellhaus konzipiert und gebaut, das mit Solar- und Windenergie versorgt wird. Im Anschluss an das Seminar wurden im Rahmen einer Zulassungsarbeit Schülerexperimente für die Sekundarstufe 1 entwickelt: Sie bieten Schülerinnen und Schülern die Möglichkeit, sich an diesem Haus und mithilfe der Experimente realitätsnah mit regenerativen Energien auseinanderzusetzen und zu erleben, dass eine sinnvolle Nutzung ein (Modell-)Haus energieautark machen kann.<br

Erratum: First fermi-LAT solar flare catalog (Astrophysical Journal, Supplement Series (2021) 252 (13) DOI: 10.3847/1538-4365/abd32e) - Ajello, Marco; Baldini, Luca; Bastieri, Denis; Bellazzini, R.; Berretta, A.; Bissaldi, Elisabetta; Blandford, R. D.; Bonino, Raffaella; Bruel, P.; Buson, S.; Cameron, R. A.; Caputo, R.; et al. (Astrophysical Journal Supplement Series, 2021)
In the published article, several references were accidentally left out of the text. The papers that we would like to cite are the following: 1. In the Introduction section, on page 2 the first sentence of the seventh paragraph should be: In this Fermi-LAT Solar Flare (FLSF) catalog we present the observations of 45 flares with >30?MeV emission in the period 2010–2018 January (covering most of the 24th solar cycle), extending on the work done by Share et al. (2018). 2. In the Results section, page 20 at the end of the first paragraph: All CME information was obtained from the CME online catalog of Gopalswamy et al. (2009, 2010). 3. In the Results section, page 23 at the end of the first paragraph: Winter et al. (2018) also reported that nearly all fast CMEs are associated with long-duration gamma-ray solar flares. 4. In subsection 4.2, Flare Series, on page 23 at the end of the paragraph: Similar results on the connection of long-lasting gamma-ray emission with SEPs were also reported by Gopalswamy et al. (2019). 5. In the Summary and Discussion section, end of list item 7: as first suggested by Gopalswamy et al. (2019). 6. In the Summary and Discussion section, after the second sentence on page 30: Fermi-LAT gamma-ray duration has been found to be correlated with the type II burst duration indicating the shock origin of the underlying electrons and ions (Gopalswamy et al. 2018). 7. In the Summary and Discussion section, at the end of the first paragraph on page 30: Further support for the CME-shock scenario has been reported by Gopalswamy et al. (2018, 2019, 2020, 2021), Kouloumvakos et al. (2020), Plotnikov et al. (2017), and Share et al. (2018). 8. In the Summary and Discussion section, at the end of the second sentence of the second paragraph on page 30, Ryan (2000) should be cited. 9. In the Summary and Discussion section, at the end of the second paragraph on page 30: Intriguing support for this scenario has been reported by Gary et al. (2018) and Grechnev et al. (2018).
CRIS-Team Scopus Importer:2021-10-29

Erratum: H.E.S.S. detection of TeV emission from the interaction region between the supernova remnant G349.7+0.2 and a molecular cloud (Astronomy and Astrophysics (2015)) - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E. O.; Backes, Michael; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; et al. (Astronomy & Astrophysics, 2015)
Keywords: Errata; addenda; Gamma rays: general; ISM: clouds; ISM: supernova remnants

Erratum: Primary particle acceleration above 100 TeV in the shell-type supernova remnant RX J1713.7-3946 with deep H.E.S.S. observations (Astronomy and Astrophysics (2007) 464 (235-243)) - Aharonian, F.; Akhperjanian, A. G.; Bazer-Bachi, A. R.; Beilicke, M.; Benbow, W.; Berge, David; Bernloehr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, Isabel V; Brion, E.; et al. (Astronomy & Astrophysics, 2011)
Keywords: acceleration of particles; cosmic rays; errata addenda; gamma rays: observations; ISM: supernova remnants

Erratum: Publisher's Note: "Electromagnetic pulse protective shielding for digital x-ray detectors" [Rev. Sci. Instrum. 94, 075106 (2023) (The Review of scientific instruments (2023) 94 7 PII: 089902) - Schreiner, Stephan; Rauch, Constantin; Akstaller, Bernhard; Bleuel, Paulina; Frojdh, Eric; Martynenko, Artem S.; Mozzanica, Aldo; Neumayer, Paul; Wegert, Leonard; Zielbauer, Bernhard; Zink, Adrian; Anton, Gisela; et al. (Review of Scientific Instruments, 2023)
CRIS-Team Scopus Importer:2023-12-22

Erratum: Publisher's Note: HESS observations of the galactic center region and their possible dark matter interpretation (Physical Review Letters (2006) 97 (221102)) - van Eldik, Christopher; et al. (Physical Review Letters, 2006)

Erratum: "Search for Dark Matter Annihilation Signals from the Fornax Galaxy Cluster with H.E.S.S.'' (2012, ApJ, 750, 123) - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; Barres De Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Bernlöhr, K.; et al. (Astrophysical Journal, 2014)

Erratum to HESS J1640-465 - an exceptionally luminous TeV γ -ray supernova remnant - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Monthly Notices of the Royal Astronomical Society, 2014)
Keywords: Addenda; Errata; ISM: individual objects: G338.3-0.0; ISM: supernova remnants; Radiation mechanisms: non-thermal

Erratum to “Results from the search for dark matter in the Milky Way with 9 years of data of the ANTARES neutrino telescope” [Phys. Lett. B 769 (2017)249–254](S037026931730254X)(10.1016/j.physletb.2017.03.063) - Albert, A.; André, M.; Anghinolfi, M.; Anton, Gisela; Ardid, M.; Aubert, J. J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; et al. (Physics Letters B, 2019)
Limits on the neutrino flux for a given mass [Formula presented] and annihilation channel are calculated as in Eq. (7)(page 252), with the integrated acceptances defined in Eq. (8)(page 252)as the effective area averaged over the neutrino energy. A numerical approximation of WIMP annihilation spectra, adapted from [1]with a too coarse binning, led to an overestimation of the integrated acceptances for dark-matter induced neutrino events. The spectra were replaced with a fine-binned version both in the likelihood and in the acceptances. The main change is a weaker limit for WIMP masses larger than 1 TeV/ [Formula presented]. Updated versions of Figs. 3–6 are provided.
CRIS-Team Scopus Importer:2019-06-04

Erratum to: Search for annihilating dark matter in the Sun with 3 years of IceCube data: IceCube Collaboration (The European Physical Journal C, (2017), 77, 3, (146), 10.1140/epjc/s10052-017-4689-9) - Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, Gisela; Archinger, M.; et al. (European Physical Journal C: Particles and Fields, 2019)
In the analysis published in 1, constraints on the number of signal events can be interpreted as constraints on the volumetric neutrino to muon conversion rate.
CRIS-Team Scopus Importer:2019-05-02

Erratum to: Search for non-relativistic magnetic monopoles with IceCube (The European Physical Journal C, (2014), 74, 7, (2938), 10.1140/epjc/s10052-014-2938-8) - Aartsen, M. G.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, Markus; Altmann, D.; Arguelles, C.; Arlen, T. C.; Auffenberg, J.; Bai, X.; Baker, M.; et al. (European Physical Journal C: Particles and Fields, 2019)
In the analyses, published in Ref. [1], the exclusion limits are calculated in dependence of the mean free path of the magnetic monopole - nucleon catalysis interaction.
CRIS-Team Scopus Importer:2019-05-02

Erratum: Using interstellar clouds to search for Galactic PeVatrons: gamma-ray signatures from supernova remnants (Monthly Notices of the Royal Astronomical Society (2021) 503 (3522–3539) DOI: 10.1093/mnras/stab667) - Mitchell, Alison; Rowell, G. P.; Celli, S.; Einecke, S. (Monthly Notices of the Royal Astronomical Society, 2023)
The paper ‘Using interstellar clouds to search for Galactic PeVatrons: gamma-ray signatures from supernova remnants’ was published in MNRAS 503 3522–3539 (2021). Following publication, a few issues were found in the numerical implementation of the described method, which influenced the predicted fluxes and the sorting of SNR–cloud pairs. Also, the catalogue values for SNR sizes are diameters, yet were interpreted as radii. These issues have now been corrected and a brief summary of revised results are presented in this erratum. Additionally, the following equations require revision: (i) A typographical error in the units for f(E, r, t) which should read cm−3GeV−1; (ii) Equation (9) contained a typographical error yet was correct in the implementation, it should read: √πRd3 f0 = (√πRd2 + 2√πRSNR2 ) Rd + 4RSNRRd2; (iii) Equation (11) should be replaced by the following equation from Reynolds (2008): RSNR(t) = 0.31 ( (n/(E1cmSN/−103)(51μerg)1/1.4) )1/5 (t/yr)2/5 pc; (iv) Equation (14) should read F(Eγ , t) = γ (Eγ , t)Vc/(4πD2 ). The combined effect of the corrections affects the shape of the curves in figs 3–5 and the predicted fluxes in subsequent figures and tables, in particular a reduction in flux at energies above 100 TeV, although the absolute flux normalization is at a comparable level for energies above 10 TeV. We provide here replacements for figs 3–5 (here Figs 1–3) and tables 2–4 (here Tables 1–3), for an integral γ -ray flux above 100 TeV. The coordinates of the cloud and SNR pairs and new predictions for the integral γ -ray flux are shown in Tables 2 and 3 and A1, with cloud properties and flux upper limits from H.E.S.S. Collaboration (2018). Replacements are also provided for figs 6 and 7 (here Figs 4 and 5). After these changes, the slow diffusion case is more favourable in generating a detectable gamma-ray flux. Indeed, in the fast diffusion case, there are no clouds predicted to have a gamma-ray flux detectable by CTA-S above 100 TeV. Consequently, we now show Figs 6 and 7 (replacements for figs 8 and 9 respectively) and Table 1 (replacement for table 2) for the slow diffusion case. Additionally, we note that after correcting the issues described above, none of the clouds have a predicted flux that violates an upper limit obtained from the HGPS in either fast or slow diffusion cases. An additional issue affecting the matching of SNRs to nearby clouds, leading to pairs listed in the original work with large angular distances or SNRs overlapping with clouds along the line-of-sight, has also been corrected in the revised tables. The discussion of section 5.1 is focused on the clouds with the brightest predicted gamma-ray flux as compared to the HGPS and in section 5.2 to HAWC observations. As the predicted fluxes are revised (see figs B1–B4), so the comparison should be interpreted in the context of these new results. From Tables 2 and 3, we see that the four clouds located at (333.46, −0.31), (16.97, 0.53), (110.43, 1.89), and (336.73, −0.98) are now the most favourable candidates for detecting a significant gamma-ray flux above 100 TeV. Further replacement figures and tables for the remaining results affected can be found in the online supplementary material.
CRIS-Team Scopus Importer:2023-06-30

Erratum: V0 production in p+A collisions at √ s=41.6 GeV (European Physical Journal C (2009) 61 (207-221) DOI: 10.1140/epjc/s10052-009-1005-3) - Abt, I.; Adams, M.; Agari, M.; Albrecht, H.; Aleksandrov, A.; Amaral, Vasco; Amorim, Antonio; Aplin, S. J.; Aushev, Volodymyr; Bagaturia, Y.; Balagura, V.; Bargiotti, M.; et al. (European Physical Journal C, 2009)

Estimating the sensitivity of the expanded OVRO-LWA array to cosmic-ray primary composition - Carvalho, W. R.; Romero-Wolf, A.; Belov, K.; D'Addario, L.; Anderson, M.; Eastwood, M.; Hallinan, G.; Kocz, J.; Lamb, J.; Monroe, R.; Nelles, Anna; Plant, K. (Proceedings of Science, 2021)
In this study we investigate the capability of the planned expansion of the Owens Valley Long Wavelength Array (OVRO-LWA) to perform radio based composition studies of the cosmic-ray flux between 50 PeV and 1 EeV. We use ZHAIRES simulations in conjunction with a method similar to the one developed by the LOFAR experiment, but that only uses radio data between 30 and 80 MHz, to reconstruct the depth of shower maximum Xmax. We found that the lower antenna densities away from the central core of the array lead to a decrease in the effective area for quality Xmax reconstructions of low zenith angle events, and that the asymmetry of the array layout creates the need for quality cuts that depend on arrival direction. We also investigate the dependence of Xmax uncertainties on shower energy and arrival direction and show that at 500 PeV it is possible to obtain Xmax uncertainties lower than 20 g/cm2 for the majority of arrival directions by using a set of simple cuts. For energies below 1017 eV, alternative reconstruction methods, such as the use of hierarchical beamforming to increase SNR or the use of arrival time measurements on the ground may be needed to maintain Xmax resolution at a desirable level.
CRIS-Team Scopus Importer:2023-08-15

Evaluation eines Unterrichtskonzepts zur Quantenoptik mit Einzelphotonenexperimenten – Ergebnisse einer Pilotstudie - Bitzenbauer, Philipp; Meyn, Jan-Peter (Naturwissenschaftliche Kompetenzen in der Gesellschaft von morgen, 2020)

Evaluation of the Weighted Mean X-ray Energy for an Imaging System Via Propagation-Based Phase-Contrast Imaging - Seifert, Maria; Weule, Mareike; Cipiccia, Silvia; Flenner, Silja; Hagemann, Johannes; Ludwig, Veronika; Michel, Thilo; Neumayer, Paul; Schuster, Max; Wolf, Andreas; Anton, Gisela; Funk, Stefan; et al. (Journal of Imaging, 2020)
For imaging events of extremely short duration, like shock waves or explosions, it is necessary to be able to image the object with a single-shot exposure. A suitable setup is given by a laser-induced X-ray source such as the one that can be found at GSI (Helmholtzzentrum fur Schwerionenforschung GmbH) in Darmstadt (Society for Heavy Ion Research), Germany. There, it is possible to direct a pulse from the high-energy laser Petawatt High Energy Laser for Heavy Ion eXperiments (PHELIX) on a tungsten wire to generate a picosecond polychromatic X-ray pulse, called backlighter. For grating-based single-shot phase-contrast imaging of shock waves or exploding wires, it is important to know the weighted mean energy of the X-ray spectrum for choosing a suitable setup. In propagation-based phase-contrast imaging the knowledge of the weighted mean energy is necessary to be able to reconstruct quantitative phase images of unknown objects. Hence, we developed a method to evaluate the weighted mean energy of the X-ray backlighter spectrum using propagation-based phase-contrast images. In a first step wave-field simulations are performed to verify the results. Furthermore, our evaluation is cross-checked with monochromatic synchrotron measurements with known energy at Diamond Light Source (DLS, Didcot, UK) for proof of concepts.
CRIS-Team WoS Importer:2020-08-28

Evaluation of X-ray phase-contrast imaging with the Medipix - Bartl, Peter; Michel, Thilo; Nachtrab, F.; Uhlmann, N.; Anton, Gisela (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011)
In the recent decade phase-contrast imaging in the X-ray regime has been developed as a competitive alternative to conventional absorption radiography and computed tomography Wilkins et al. (1996) [1]. As phase-contrast is an energy dependent phenomenon, the use of a spectroscopic detector like the Medipix is a key tool to characterize and optimize imaging methods such as in-line or interferometric phase-contrast imaging. In the following the energy dependency of interference patterns caused by phase shifts in a coherent wavefront will be shown. Moreover, the spatial coherence of X-rays, considered as wavefronts, is crucial for the formation of detectable interference effects. The newest generations of X-ray sources produce small but finite focal spot sizes, so that partial spatial coherence of the wave-field has to be taken into account. The contribution of partial coherence to the image recorded in the detector plane has been investigated and the outcome will be presented. For a fuller understanding of a complete phase-contrast imaging setup the incoherent scattering effects were additionally simulated with Monte-Carlo methods. Furthermore, to develop a realistic simulation-tool for X-ray phase-contrast imaging, a good comprehension of the detection system is needed. This was also achieved by Monte-Carlo simulations. The comparison with measurements of the simulations of a complete setup shows a very good agreement.
EAM Import::2019-03-14

Event reconstruction for KM3NeT/ORCA using convolutional neural networks - Aiello, S.; Albert, A.; Garre, S. Alves; Aly, Z.; Ameli, F.; Andre, M.; Androulakis, G.; Anghinolfi, M.; Anguita, M.; Anton, Gisela; Ardid, M.; Aublin, J.; et al. (Journal of Instrumentation, 2020)
The KM3NeT research infrastructure is currently under construction at two locations in the Mediterranean Sea. The KM3NeT/ORCA water-Cherenkov neutrino detector off the French coast will instrument several megatons of seawater with photosensors. Its main objective is the determination of the neutrino mass ordering. This work aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided. It is shown that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches.
CRIS-Team WoS Importer:2020-10-30

Event reconstruction in a liquid xenon Time Projection Chamber with an optically-open field cage - Stiegler, T.; Sangiorgio, S.; Brodsky, J. P.; Heffner, M.; Kharusi, S. Al; Anton, Gisela; Arnquist, I. J.; Badhrees, I.; Barbeau, P. S.; Beck, D.; Belov, V.; Bhatta, T.; et al. (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2021)
nEXO is a proposed tonne-scale neutrinoless double beta decay (0νββ) experiment using liquid 136Xe (LXe) in a Time Projection Chamber (TPC) to read out ionization and scintillation signals. Between the field cage and the LXe vessel, a layer of LXe (“skin” LXe) is present, where no ionization signal is collected. Only scintillation photons are detected, owing to the lack of optical barrier around the field cage. In this work, we show that the light originating in the skin LXe region can be used to improve background discrimination by 5% over previous published estimates. This improvement comes from two elements. First, a fraction of the γ-ray background is removed by identifying light from interactions with an energy deposition in the skin LXe. Second, background from 222Rn dissolved in the skin LXe can be efficiently rejected by tagging the α decay in the 214Bi-214Po chain in the skin LXe.
CRIS-Team Scopus Importer:2021-04-02
Keywords: Liquid xenon detectors; Monte Carlo methods; Neutrinoless double beta decay; Time-projection chambers

Evidence for a parity doublet Delta(1920)Rho33 and Delta(1940)Delta33 from gamma-rho -> rho-pi0eta - Horn, I.; Anisovich, A. V.; Anton, Gisela; Bantes, R.; Bartholomy, O.; Beck, R.; Beloglazov, Yu.; Bogendörfer, Regina; Castelijns, R.; Crede, V.; Ehmanns, A.; Ernst, J.; et al. (Physical Review Letters, 2008)

Evidence for neutrino emission from the nearby active galaxy NGC 1068 - Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alameddine, J. M.; Alispach, C.; Alves, A. A.; Amin, N. M.; Andeen, K.; Anderson, T.; et al. (Science, 2022)
A supermassive black hole, obscured by cosmic dust, powers the nearby active galaxy NGC 1068. Neutrinos, which rarely interact with matter, could provide information on the galaxy's active core. We searched for neutrino emission from astrophysical objects using data recorded with the IceCube neutrino detector between 2011 and 2020. The positions of 110 known gamma-ray sources were individually searched for neutrino detections above atmospheric and cosmic backgrounds. We found that NGC 1068 has an excess of 79(-20)(+22) neutrinos at tera-electron volt energies, with a global significance of 4.2 sigma, which we interpret as associated with the active galaxy. The flux of high-energy neutrinos that we measured from NGC 1068 is more than an order of magnitude higher than the upper limit on emissions of tera-electron volt gamma rays from this source.
CRIS-Team WoS Importer:2023-01-27

Evidence for VHE γ-ray emission from the distant BL Lac PG 1553+113 - van Eldik, Christopher; et al. (Astronomy & Astrophysics, 2006)
The high-frequency peaked BL Lac PG 1553+113 was observed in 2005 with the HESS stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. Using the HESS standard analysis, an excess was measured at the 4.0σ level in these observations (7.6 hours live time). Three alternative, lower-threshold analyses yield >5σ excesses. The observed integral flux above 200 GeV is (4.8 ± 1.3 ± 1.0) × 10 cm s, and shows no evidence for variability. The measured energy spectrum is characterized by a very soft power law (photon index of Γ = 4.0 ± 0.6). Although the redshift of PG 1553+113 is unknown, there are strong indications that it is greater than z = 0.25 and possibly larger than z = 0.78. The observed spectrum is interpreted in the context of VHE γ-ray absorption by the Extragalactic Background Light, and is used to place an upper limit on the redshift of z < 0.74. © ESO 2006.
Keywords: BL Lacertae objects: individual: PG 1553+113; Galaxies: active; Gamma rays: observations

Evidence for γ-ray emission from the remnant of Kepleras supernova based on deep H.E.S.S. observations - Aharonian, F.; Benkhali, F. Ait; Angüner, E. O.; Ashkar, H.; Backes, M.; Martins, V. Barbosa; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Böttcher, M.; Boisson, C.; et al. (Astronomy & Astrophysics, 2022)
Observations with imaging atmospheric Cherenkov telescopes (IACTs) have enhanced our knowledge of nearby supernova (SN) remnants with ages younger than 500 yr by establishing Cassiopeia A and the remnant of Tychoas SN as very-high-energy (VHE) ?-ray sources. The remnant of Kepleras SN, which is the product of the most recent naked-eye SN in our Galaxy, is comparable in age to the other two, but is significantly more distant. If the ?-ray luminosities of the remnants of Tychoas and Kepleras SNe are similar, then the latter is expected to be one of the faintest ?-ray sources within reach of the current generation IACT arrays. Here we report evidence at a statistical level of 4.6? for a VHE signal from the remnant of Kepleras SN based on deep observations by the High Energy Stereoscopic System (H.E.S.S.) with an exposure of 152 h. The measured integral flux above an energy of 226 GeV is ?0.3% of the flux of the Crab Nebula. The spectral energy distribution (SED) reveals a ?-ray emitting component connecting the VHE emission observed with H.E.S.S.To the emission observed at GeV energies with Fermi-LAT. The overall SED is similar to that of the remnant of Tychoas SN, possibly indicating the same nonthermal emission processes acting in both these young remnants of thermonuclear SNe.
CRIS-Team Scopus Importer:2022-07-15
Keywords: Gamma rays: General; Ism: Supernova remnants; Radiation mechanisms: Non-Thermal; Supernovae: Individual: Kepler

Evidence of 200 TeV photons from HAWC J1825-134 - Albert, A.; Alfaro, R.; Alvarez, C.; Camacho, J. R. Angeles; Arteaga-Velazquez, J. C.; Arunbabu, K. P.; Rojas, D. Avila; Ayala Solares, H. A.; Baghmanyan, V.; Belmont-Moreno, E.; Benzvi, S. Y.; Brisbois, C.; et al. (Astrophysical Journal Letters, 2021)
The Earth is bombarded by ultrarelativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=1015 eV), the knee in the particle spectrum, are believed to have a Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV γ-rays from decaying π0, produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cerenkov (HAWC) observatory of the γ-ray source, HAWC J1825-134, whose energy spectrum extends well beyond 200 TeV without a break or cutoff. The source is found to be coincident with a giant molecular cloud. The ambient gas density is as high as 700 protons cm-3. While the nature of this extreme accelerator remains unclear, CRs accelerated to energies of several PeV colliding with the ambient gas likely produce the observed radiation.
CRIS-Team Scopus Importer:2021-02-26

Evidence that Ultra-high-energy Gamma Rays Are a Universal Feature near Powerful Pulsars - Albert, A.; Alfaro, R.; Alvarez, C.; Alvarez, J. D.; Angeles Camacho, J. R.; Arteaga-Velazquez, J. C.; Arunbabu, K. P.; Rojas, D. Avila; Ayala Solares, H. A.; Baghmanyan, V.; Belmont-Moreno, E.; Benzvi, S. Y.; et al. (Astrophysical Journal Letters, 2021)
The highest-energy known gamma-ray sources are all located within 0.°5 of extremely powerful pulsars. This raises the question of whether ultra-high-energy (UHE; >56 TeV) gamma-ray emission is a universal feature expected near pulsars with a high spin-down power. Using four years of data from the High Altitude Water Cherenkov Gamma-Ray Observatory, we present a joint-likelihood analysis of 10 extremely powerful pulsars to search for subthreshold UHE gamma-ray emission correlated with these locations. We report a significant detection (>3σ), indicating that UHE gamma-ray emission is a generic feature of powerful pulsars. We discuss the emission mechanisms of the gamma rays and the implications of this result. The individual environment, such as the magnetic field and particle density in the surrounding area, appears to play a role in the amount of emission.
CRIS-Team Scopus Importer:2021-05-14

Examination of the production of an isotensor dibaryon in the pp -> pp pi(+)pi(-) reaction - Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F. S.; Berlowski, M.; Bondar, A.; Buescher, M.; Calen, H.; Ciepal, I.; Clement, H.; Czerwinski, E.; et al. (Physical Review C - Nuclear Physics, 2019)
The quasifree pp -> pp pi(+)pi(-) reaction has been measured by means of pd collisions at T-p = 1.2 GeV using the WASA detector setup at COSY enabling exclusive and kinematically complete measurements. Total and differential cross sections have been extracted for the energy region T-p = 1.08-1.36 GeV (root s = 2.35-2.46 GeV) covering thus the regions of N* (1440 ) and Delta(1232)Delta(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange as well as isospin relations based on the pp -> pp pi(0)pi(0) data underpredict substantially the measured total cross section. The calculations are also at variance with specific experimental differential cross sections. An isotensor Delta N dibaryon resonance with I(J(P)) = 2(1(+) ) produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong [Phys. Rev. Lett. 13, 815 (1964)] and more recently calculated by A. Gal and H. Garcilazo [Nucl. Phys. A 928, 73 (2014)].
CRIS-Team WoS Importer:2019-02-21

Examination of the production of an isotensor dibaryon in the pp→ppπ+π- reaction - Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, Mikhail; Bergmann, F. S.; Berlowski, M.; Bondar, A.; Buescher, M.; Calen, H.; Ciepal, I.; Clement, H.; Czerwinski, E.; et al. (Physical Review C - Nuclear Physics, 2019)
The quasifree pp→ppπ+π- reaction has been measured by means of pd collisions at Tp=1.2GeV using the WASA detector setup at COSY enabling exclusive and kinematically complete measurements. Total and differential cross sections have been extracted for the energy region Tp=1.08-1.36 GeV (s=2.35-2.46GeV) covering thus the regions of N∗(1440) and Δ(1232)Δ(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange as well as isospin relations based on the pp→ppπ0π0 data underpredict substantially the measured total cross section. The calculations are also at variance with specific experimental differential cross sections. An isotensor ΔN dibaryon resonance with I(JP)=2(1+) produced associatedly with a pion is able to overcome these deficiencies. Such a dibaryon was predicted by Dyson and Xuong [Phys. Rev. Lett. 13, 815 (1964)PRLTAO0031-900710.1103/PhysRevLett.13.815] and more recently calculated by A. Gal and H. Garcilazo [Nucl. Phys. A 928, 73 (2014)NUPABL0375-947410.1016/j.nuclphysa.2014.02.019].
CRIS-Team Scopus Importer:2019-05-02

Expansion cone for the 3-inch PMTs of the KM3NeT optical modules - Adrian-Martinez, S.; Ageron, M.; Aguilar, J. A.; Aharonian, F.; Aiello, S.; Albert, A.; Alexandri, M.; Ameli, F.; Anassontzis, E. G.; Anghinolfi, M.; Anton, Gisela; Anvar, S.; et al. (Journal of Instrumentation, 2013)
Detection of high-energy neutrinos from distant astrophysical sources will open a new window on the Universe. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter containing the telescope. A novel multi-PMT digital optical module (DOM) was developed to contain 31 3-inch photomultiplier tubes (PMTs). In order to maximize the detector sensitivity, each PMT will be surrounded by an expansion cone which collects photons that would otherwise miss the photocathode. Results for various angles of incidence with respect to the PMT surface indicate an increase in collection efficiency by 30% on average for angles up to 45 degrees with respect to the perpendicular. Ray-tracing calculations could reproduce the measurements, allowing to estimate an increase in the overall photocathode sensitivity, integrated over all angles of incidence, by 27% (for a single PMT). Prototype DOMs, being built by the KM3NeT consortium, will be equipped with these expansion cones.
Keywords: Optical detector readout concepts; Instrument optimisation; Cherenkov detectors; Large detector systems for particle and astroparticle physics

Experimentelle Quantenphysik im Physikunterricht - Strunz, Andreas; Meyn, Jan-Peter (Praxis der Naturwissenschaften - Physik in der Schule, 2015)
Wir demonstrieren die Quantennatur des Lichts mit einer neu entwickelten Apparatur im Klassenzimmer. Einzelphotonenzustände werden mit einer Koinzidenzmethode präpariert. Die Auswertung von Signalen zweier Detektoren hinter einem halbdurchlässigen Spiegel ergibt eine Antikorrelation, die als Reflexion oder Tranmission einer unteilbaren Lichtportion interpretiert wird. Dass es sich dabei nicht um mechanistisch gedachte Teilchen handeln kann, ergibt die anschließende Interferenz in einem Michelson-Interferometer. Experimentelle Methoden und Begriffe entsprechen dem aktuellen Stand der Physik.

Experimente skalieren - Meyn, Jan-Peter (Praxis der Naturwissenschaften - Physik in der Schule, 2014)
UnivIS-Import:2015-04-02:Pub.2014.nat.dphy.PI.PDP.experi

Experimente skalieren - Meyn, Jan-Peter (PLUS LUCIS, 2015)

Exploration of different x-ray Talbot-Lau setups for dark-field lung imaging examined in a porcine lung - Ludwig, Veronika; Seifert, Maria; Hauke, Christian; Hellbach, Katharina; Horn, Florian; Pelzer, Georg; Radicke, Marcus; Rieger, Jens; Sutter, Sven-Martin; Michel, Thilo; Anton, Gisela (Physics in Medicine and Biology, 2019)
X-ray dark-field imaging is a promising technique for lung diagnosis. Due to the alveolar structure of lung tissue, a higher contrast is obtained by the dark-field image compared to the attenuation image. Animal studies indicate an enhancement regarding the detection of lung diseases in early stages. In this publication, we focus on the influence of different Talbot-Lau interferometer specifications while maintaining the x-ray source, sample magnification and detector system. By imaging the same porcine lung with three different grating sets, we analyze the contrast-to-noise ratio of the obtained dark-field images with respect to visibility and correlation length. We demonstrate that relatively large grating periods of the phase and of the analyzer grating are sufficient for high quality lung imaging at reasonable dose levels.
CRIS-Team WoS Importer:2019-03-29

Exploring a SNR/molecular cloud association within HESS J1745-303 - Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, Wystan; Bernloehr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, Isabel V; et al. (Astronomy & Astrophysics, 2008)
Aims. HESS J1745-303 is an extended, unidentified VHE (very high energy) gamma-ray source discovered using HESS in the Galactic Plane Survey. Since no obvious counterpart has previously been found in longer-wavelength data, the processes that power the VHE emission are not well understood.Methods. Combining the latest VHE data with recent XMM-Newton observations and a variety of source catalogs and lower-energy survey data, we attempt to match (from an energetic and positional standpoint) the various parts of the emission of HESS J1745-303 with possible candidates.Results. Though no single counterpart is found to fully explain the VHE emission, we postulate that at least a fraction of the VHE source may be explained by a supernova-remnant/molecular-cloud association and/or a high-spin-down-flux pulsar. © 2008 ESO.
Keywords: Galaxy: general; Gamma rays: observations; ISM: clouds; ISM: cosmic rays; X-rays: general

Exploring German Secondary School Students’ Conceptual Knowledge of Density - Zenger, Tim; Bitzenbauer, Philipp (Science Education International, 2022)
This article reports on the development and piloting of a German version of a concept test to assess students’ conceptual knowledge of density. The concept test was administered in paper-pencil format to 222 German secondary school students as a post-test after instruction in all relevant concepts of density. We provide a psychometric characterization of the instrument based on the student responses. Therefore, we use methods from classical test theory and item response theory. Our analysis shows that our concept test has good psychometric properties. Furthermore, it is shown to enable a reliable (α= 0.77) survey of students’ conceptual knowledge of density. Finally, we use the student responses to identify secondary school students’ difficulties with the density concept. We replicate student difficulties on density from the literature, but our study also reveals some new difficulties.<br
Keywords: concept inventory; student difficulties; density

Exploring the Relationship Between Surface Features and Explaining Quality of YouTube Explanatory Videos - Bitzenbauer, Philipp; Höfler, Sebastian; Veith, Joaquin M.; Winkler, Bianca; Zenger, Tim; Kulgemeyer, Christoph (International Journal of Science and Mathematics Education, 2023)
Physics education research on explanatory videos has experienced a boost in recent years. Due to the vast number of explanatory videos available online, e.g. on YouTube, finding videos of high explaining quality is a challenging task for learners, teachers, and lecturers alike. Prior research on the explaining quality of explanatory videos on classical mechanics topics has uncovered that the surface features provided by YouTube (e.g. number of views or likes) do not seem to be suitable indicators of the videos’ explaining quality. Instead, the number of content-related comments was found to be statistically significantly correlated with the explaining quality. To date, these findings have only been observed in the context of explanatory videos on classical mechanics topics. The question arises whether similar correlations between the explaining quality and YouTube surface features can be found for videos on topics that are difficult to access visually and verbally, for example from quantum physics. Therefore, we conducted an exploratory study analyzing the explaining quality of N = 60 YouTube videos on quantum entanglement and tunnelling. To this end, we made use of a category-based measure of explanatory videos’ explaining quality from the literature. We report correlations between the videos’ explaining quality and the surface features provided by YouTube. On the one hand, our results substantiate earlier findings for mechanics topics. On other hand, partial correlations shed new light on the relationship between YouTube’s surface features and explaining quality of explanatory videos.
CRIS-Team Scopus Importer:2023-03-03
Keywords: Entanglement; Explaining quality; Explanatory videos; Quantum physics; Surface features; Tunnelling

Extended Gamma-Ray Emission from the G25.0+0.0 Region: A Star-forming Region Powered by the Newly Found OB Association? - Katsuta, J.; Uchiyama, Y.; Funk, Stefan (Astrophysical Journal, 2017)
We report a study of extended gamma-ray emission with the Large Area Telescope (LAT) on board the Fermi Gammaray Space Telescope, which is likely to be the second case of gamma-ray detection from a star-forming region (SFR) in our Galaxy. The LAT source is located in the G25 region, 1 degrees.7. x. 2 degrees.1 around (l, b) = (25 degrees.0, 0 degrees.0). The gamma-ray emission is found to be composed of two extended sources and one pointlike source. The extended sources have similar sizes of about 1 degrees.4. x. 0 degrees.1. An similar to 0 degrees.4 diameter subregion of one has a photon index of Gamma = 1.53 +/- 0.15, and is spatially coincident with HESS J1837-069, likely a pulsar wind nebula. The other parts of the extended sources have a photon index of Gamma = 2.1 +/- 0.2 without significant spectral curvature. Given their spatial and spectral properties, they have no clear associations with sources at other wavelengths. Their gamma-ray properties are similar to those of the Cygnus cocoon SFR, the only firmly established gamma-ray detection of an SFR in the Galaxy. Indeed, we find bubble-like structures of atomic and molecular gas in G25, which may be created by a putative OB association/cluster. The gamma-ray emitting regions appear confined in the bubble-like structure; similar properties are also found in the Cygnus cocoon. In addition, using observations with the XMM-Newton, we find a candidate young massive OB association/cluster G25.18+0.26 in the G25 region. We propose that the extended gamma-ray emission in G25 is associated with an SFR driven by G25.18+0.26. Based on this scenario, we discuss possible acceleration processes in the SFR and compare them with the Cygnus cocoon.
CRIS-Team WoS Importer:2020-01-15

Extended VHE gamma-ray emission towards SGR1806-20, LBV 1806-20, and stellar cluster Cl*1806-20 - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; et al. (Astronomy & Astrophysics, 2018)
Using the High Energy Spectroscopic System (H.E.S.S.) telescopes we have discovered a steady and extended very high-energy (VHE) gamma-ray source towards the luminous blue variable candidate LBV 1806-20, massive stellar cluster Cl* 1806-20, and magnetar SGR 1806-20. The new VHE source, HESS J1808-204, was detected at a statistical significance of >6 sigma (post-trial) with a photon flux normalisation (2.9 +/- 0.4(stat) +/- 0.5(sys)) x 10(-13) ph cm(-2) s(-1) TeV-1 at 1 TeV and a power-law photon index of 2.3 +/- 0.2(stat) +/- 0.3(sys). The luminosity of this source (0.2 to 10 TeV; scaled to distance d = 8 : 7 kpc) is L-VHE similar to 1.6 x 10(34)(d = 8.7 kpc)(2) erg s(-1). The VHE gamma-ray emission is extended and is well fit by a single Gaussian with statistical standard deviation of 0.095 degrees +/- 0.015 degrees. This extension is similar to that of the synchrotron radio nebula G10.0-0.3, which is thought to be powered by LBV 1806-20. The VHE gamma-ray luminosity could be provided by the stellar wind luminosity of LBV 1806-20 by itself and/or the massive star members of Cl* 1806-20. Alternatively, magnetic dissipation (e.g. via reconnection) from SGR 1806-20 can potentially account for the VHE luminosity. The origin and hadronic and/or leptonic nature of the accelerated particles responsible for HESS J1808-204 is not yet clear. If associated with SGR 1806 20, the potentially young age of the magnetar (650 yr) can be used to infer the transport limits of these particles to match the VHE source size. This discovery provides new interest in the potential for high-energy particle acceleration from magnetars, massive stars, and/or stellar clusters.
Keywords: gamma rays: general; stars: magnetars; stars: massive

Fan-beam Projection Image Acquisition using MRI - Syben-Leisner, Christopher; Stimpel, Bernhard; Leghissa, Martino; Dörfler, Arnd; Maier, Andreas (3rd Conference on Image-Guided Interventions & Fokus Neuroradiologie, 2017)
UnivIS-Import:2017-12-18:Pub.2017.tech.IMMD.IMMD5.fanbea_5

Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow - Ajello, M.; Arimoto, M.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Berretta, A.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bottacini, E.; et al. (Astrophysical Journal, 2020)
We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.
CRIS-Team Scopus Importer:2020-04-03

FERMI LARGE AREA TELESCOPE DETECTION OF A BREAK IN THE GAMMA-RAY SPECTRUM OF THE SUPERNOVA REMNANT CASSIOPEIA A - Yuan, Yajie; Funk, Stefan; Johannesson, Guelauger; Lande, Joshua; Tibaldo, Luigi; Uchiyama, Yasunobu (Astrophysical Journal, 2013)
We report on observations of the supernova remnant Cassiopeia A in the energy range from 100 MeV to 100 GeV using 44 months of observations from the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. We perform a detailed spectral analysis of this source and report on a low-energy break in the spectrum at 1.72(-0.89)(+1.35) GeV. By comparing the results with models for the gamma-ray emission, we find that hadronic emission is preferred for the GeV energy range.
Keywords: acceleration of particles; gamma rays: general; ISM: supernova remnants; radiation mechanisms: non-thermal; supernovae: individual (Cassiopeia A)

FERMI LARGE AREA TELESCOPE DETECTION OF EXTENDED GAMMA-RAY EMISSION FROM THE RADIO GALAXY FORNAX A - Ackermann, M.; Ajello, Marco; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Brandt, T. J.; et al. (Astrophysical Journal, 2016)
We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax. A using 6.1 years of Pass. 8 data. After Centaurus. A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be < 14% of the total gamma-ray flux. A preferred alignment of the gamma-ray elongation with the radio lobes was demonstrated by rotating the radio lobes template. We found no significant evidence for variability on similar to 0.5 year timescales. Taken together, these results strongly suggest a lobe origin for the gamma-rays. With the extended nature of the > 100 MeV gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus. A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about similar to 2-3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus required, and could be due to hadronic emission arising from proton-proton collisions of cosmic rays with thermal plasma within the radio lobes.
Keywords: galaxies: active; galaxies: individual (Fornax A); galaxies: jets; gamma rays: galaxies; radiation mechanisms: non-thermal

Fermi Large Area Telescope Fourth Source Catalog - Abdollahi, S.; Acero, F.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Becerra Gonzalez, J.; Bellazzini, R.; et al. (Astrophysical Journal Supplement Series, 2020)
We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
CRIS-Team WoS Importer:2020-04-03

Fermi Large Area Telescope Performance after 10 Years of Operation - Ajello, M.; Atwood, W. B.; Axelsson, M.; Bagagli, R.; Bagni, M.; Baldini, L.; Bastieri, D.; Bellardi, F.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonino, Raffaella; et al. (Astrophysical Journal Supplement Series, 2021)
The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.
CRIS-Team WoS Importer:2021-09-17

FERMI LARGE AREA TELESCOPE STUDY OF COSMIC-RAYS AND THE INTERSTELLAR MEDIUM IN NEARBY MOLECULAR CLOUDS (vol 755, 22, 2012) - Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; et al. (Astrophysical Journal, 2013)

FERMI LARGE AREA TELESCOPE THIRD SOURCE CATALOG - Acero, F.; Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, Denis; Belfiore, A.; Bellazzini, R.; et al. (Astrophysical Journal Supplement Series, 2015)
We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in the 100 MeV-300 GeV range. Based on the first 4 yr of science data from the Fermi Gamma-ray Space Telescope mission, it is the deepest yet in this energy range. Relative to the Second Fermi LAT catalog, the 3FGL catalog incorporates twice as much data, as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for Galactic diffuse.-ray emission, a refined procedure for source detection, and improved methods for associating LAT sources with potential counterparts at other wavelengths. The 3FGL catalog includes 3033 sources above 4 sigma significance, with source location regions, spectral properties, and monthly light curves for each. Of these, 78 are flagged as potentially being due to imperfections in the model for Galactic diffuse emission. Twenty-five sources are modeled explicitly as spatially extended, and overall 238 sources are considered as identified based on angular extent or correlated variability (periodic or otherwise) observed at other wavelengths. For 1010 sources we have not found plausible counterparts at other wavelengths. More than 1100 of the identified or associated sources are active galaxies of the blazar class; several other classes of non-blazar active galaxies are also represented in the 3FGL. Pulsars represent the largest Galactic source class. From source counts of Galactic sources we estimate that the contribution of unresolved sources to the Galactic diffuse emission is similar to 3% at 1 GeV.
Keywords: catalogs; gamma-rays: general

Fermi-LAT Observations of LIGO/Virgo Event GW170817 - Ajello, Marco; Allafort, A.; Axelsson, M.; Baldini, Luca; Barbiellini, G.; Baring, M. G.; Bastieri, Denis; Bellazzini, R.; Berenji, B.; Bissaldi, Elisabetta; Blandford, R. D.; Bloom, E. D.; et al. (Astrophysical Journal, 2018)
We present the Fermi Large Area Telescope (LAT) observations of the binary neutron star merger event GW170817 and the associated short gamma-ray burst (SGRB) GRB 170817A detected by the Fermi Gamma-ray Burst Monitor. The LAT was entering the South Atlantic Anomaly at the time of the LIGO/Virgo trigger (t(GW)) and therefore cannot place constraints on the existence of high-energy (E > 100 MeV) emission associated with the moment of binary coalescence. We focus instead on constraining high-energy emission on longer timescales. No candidate electromagnetic counterpart was detected by the LAT on timescales of minutes, hours, or days after the LIGO/Virgo detection. The resulting flux upper bound (at 95% C. L.) from the LAT is 4.5. x. 10(-10) erg cm(-2) s(-1) in the 0.1-1 GeV range covering a period from tGW. +. 1153 s to t(GW). +. 2027 s. At the distance of GRB 170817A, this flux upper bound corresponds to a luminosity upper bound of 9.7. x. 10(43) erg s(-1), which is five orders of magnitude less luminous than the only other LAT SGRB with known redshift, GRB 090510. We also discuss the prospects for LAT detection of electromagnetic counterparts to future gravitational-wave events from Advanced LIGO/Virgo in the context of GW170817/GRB 170817A.
Keywords: gamma-ray burst: general; gamma rays: general; gravitational waves

Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A - Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; et al. (Science, 2014)
The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

FERMI-LAT OBSERVATIONS OF THE LIGO EVENT GW150914 - Ackermann, M.; Ajello, Marco; Albert, A.; Anderson, B.; Arimoto, M.; Atwood, W. B.; Axelsson, M.; Baldini, Luca; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; et al. (Astrophysical Journal Letters, 2016)
The Fermi Large Area Telescope (LAT) has an instantaneous field of view (FoV) covering similar to 1/5 of the sky and it completes a survey of the entire sky in high-energy gamma-rays every 3 hr. It enables searches for transient phenomena over timescales from milliseconds to years. Among these phenomena could be electromagnetic counterparts to gravitational wave (GW) sources. In this paper, we present a detailed study of the LAT observations relevant to Laser Interferometer Gravitational-wave Observatory (LIGO) event GW150914, which is the first direct detection of gravitational waves and has been interpreted as being due to the coalescence of two stellar-mass black holes. The localization region for GW150914 was outside the LAT FoV at the time of the GW signal. However, as part of routine survey observations, the LAT observed the entire LIGO localization region within similar to 70 minutes of the trigger and thus enabled a comprehensive search for a.-ray counterpart to GW150914. The study of the LAT data presented here did not find any potential counterparts to GW150914, but it did provide limits on the presence of a transient counterpart above 100 MeV on timescales of hours to days over the entire GW150914 localization region.
Keywords: gamma-ray burst: general; gamma-rays: general; gravitational waves; methods: observational

FERMI LAT STACKING ANALYSIS OF SWIFT LOCALIZED GRBs - Ackermann, M.; Ajello, M.; Anderson, B.; Atwood, W. B.; Axelsson, M.; Baldini, Luca; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bhat, P. N.; Bissaldi, Elisabetta; Bonino, R.; et al. (Astrophysical Journal, 2016)
We perform a comprehensive stacking analysis of data collected by the Fermi. Large Area Telescope (LAT) of gamma-ray bursts (GRBs) localized by the Swift. spacecraft, which were not detected by the LAT but which fell within the instrument's field of view at the time of trigger. We examine a total of 79 GRBs by comparing the observed counts over a range of time intervals to that expected from designated background orbits, as well as by using a joint likelihood technique to model the expected distribution of stacked counts. We find strong evidence for subthreshold emission at MeV to GeV energies using both techniques. This observed excess is detected during intervals that include and exceed the durations typically characterizing the prompt emission observed at keV energies and lasts at least 2700 s after the co-aligned burst trigger. By utilizing a novel cumulative likelihood analysis, we find that although a burst's prompt gamma-ray and afterglow X-ray flux both correlate with the strength of the subthreshold emission, the X-ray afterglow flux measured by Swift's X-ray Telescope at 11 hr post trigger correlates far more significantly. Overall, the extended nature of the subthreshold emission and its connection to the burst's afterglow brightness lend. further support to the external forward shock origin of the late-time emission detected by the LAT. These results suggest that the extended high-energy emission observed by the LAT may be a relatively common feature but remains undetected in a majority of bursts owing. to instrumental threshold effects.
Keywords: gamma-ray burst: general; gamma rays: general; methods: data analysis; X-rays: bursts

Final characterisation and design of the Gamma-ray Cherenkov Telescope (GCT) for the Cherenkov Telescope Array - Le Blanc, O.; Fasola, G.; Huet, J. M.; White, Richard; Dmytriiev, A.; Sol, H.; Zech, A.; Abchiche, A.; Amans, J. P.; Armstrong, T. P.; Barcelo, M.; Berge, D.; et al. (GROUND-BASED AND AIRBORNE TELESCOPES VII, 2018)
CRIS-Team WoS Importer:2020-01-15

First all-flavor neutrino pointlike source search with the ANTARES neutrino telescope - Albert, A.; Andre, M.; Anghinolfi, M.; Anton, Gisela; Ardid, M.; Aubert, J. -J.; Avgitas, T.; Baret, B.; Barrios-Marti, J.; Basa, S.; Belhorma, B.; Bertin, V.; et al. (Physical Review D - Particles, Fields, Gravitation and Cosmology, 2017)
A search for cosmic neutrino sources using the data collected with the ANTARES neutrino telescope between early 2007 and the end of 2015 is performed. For the first time, all neutrino interactions-charged and neutral-current interactions of all flavors-are considered in a search for point-like sources with the ANTARES detector. In previous analyses, only muon neutrino charged-current interactions were used. This is achieved by using a novel reconstruction algorithm for shower-like events in addition to the standard muon track reconstruction. The shower channel contributes about 23% of all signal events for an E-2 energy spectrum. No significant excess over background is found. The most signal-like cluster of events is located at (alpha, delta) = (343.8 degrees, 23.5 degrees) with a significance of 1.9 sigma. The neutrino flux sensitivity of the search is about E(2)d Phi/dE = 6 x 10(-9) GeV cm(-2) s(-1) for declinations from -90 degrees up to -42 degrees, and below 10(-8) GeV cm(-2) s(-1) for declinations up to 5 degrees. The directions of 106 source candidates and 13 muon track events from the IceCube high-energy sample events are investigated for a possible neutrino signal and upper limits on the signal flux are determined.

First all-flavor search for transient neutrino emission using 3-years of IceCube DeepCore data - Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alispach, C.; Alves, A. A.; Amin, N. M.; Andeen, K.; Anderson, T.; Ansseau, I.; et al. (Journal of Cosmology and Astroparticle Physics, 2022)
Since the discovery of a flux of high-energy astrophysical neutrinos, searches for their origins have focused primarily at TeV-PeV energies. Compared to sub-TeV searches, high-energy searches benefit from an increase in the neutrino cross section, improved angular resolution on the neutrino direction, and a reduced background from atmospheric neutrinos and muons. However, the focus on high energy does not preclude the existence of sub-TeV neutrino emission where IceCube retains sensitivity. Here we present the first all-flavor search from IceCube for transient emission of low-energy neutrinos, focusing on the energy region of 5.6-100 GeV using three years of data obtained with the IceCube-DeepCore detector. We find no evidence of transient neutrino emission in the data, thus leading to a constraint on the volumetric rate of astrophysical transient sources in the range of ∼ 705-2301 Gpc-3 yr-1 for sources following a subphotospheric energy spectrum with a mean energy of 100 GeV and a bolometric energy of 1052 erg.
CRIS-Team Scopus Importer:2022-02-11
Keywords: gamma ray burst experiments; neutrino astronomy; neutrino experiments

First detection of a VHE gamma-ray spectral maximum from a cosmic source: HESS discovery of the Vela X nebula - van Eldik, Christopher; et al. (Astronomy & Astrophysics, 2006)
The Vela supernova remnant (SNR) is a complex region containing a number of sources of non-thermal radiation. The inner section of this SNR, within 2 degrees of the pulsar PSR B0833-45, has been observed by the HESS γ-ray atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from an extended region to the south of the pulsar, within an integration region of radius 0.8° around the position (α = 0835 00, δ = -45°36′ J2000.0). The excess coincides with a region of hard X-ray emission seen by the ROSAT and ASCA satellites. The observed energy spectrum of the source between 550 GeV and 65 TeV is well fit by a power law function with photon index Γ = 1.45 ± 0.09 ± 0.2 and an exponential cutoff at an energy of 13.8 ± 2.3 ± 4.1 TeV. The integral flux above 1 TeV is (1.28 ± 0.17 ± 0.38) × 10 cm s. This result is the first clear measurement of a peak in the spectral energy distribution from a VHE γ-ray source, likely related to inverse Compton emission. A fit of an Inverse Compton model to the HESS spectral energy distribution gives a total energy in non-thermal electrons of ∼2 × 10 erg between 5 TeV and 100 TeV, assuming a distance of 290 parsec to the pulsar. The best fit electron power law index is 2.0, with a spectral break at 67 TeV. © ESO 2006.
Keywords: Gamma rays: observations; Ism: plerions

First detection of VHE γ-rays from SN 1006 by HESS - Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Beilicke, M.; Bernloehr, K.; Bochow, A.; Boisson, C.; et al. (Astronomy & Astrophysics, 2010)
Aims. Recent theoretical predictions of the lowest very high energy (VHE) luminosity of SN 1006 are only a factor 5 below the previously published HESS upper limit, thus motivating further in-depth observations of this source. Methods. Deep observations at VHE energies (above 100 GeV) were carried out with the high energy stereoscopic system (HESS) of Cherenkov Telescopes from 2003 to 2008. More than 100 h of data have been collected and subjected to an improved analysis procedure. Results. Observations resulted in the detection of VHE γ-rays from SN 1006. The measured γ-ray spectrum is compatible with a power-law, the flux is of the order of 1% of that detected from the Crab Nebula, and is thus consistent with the previously established HESS upper limit. The source exhibits a bipolar morphology, which is strongly correlated with non-thermal X-rays. Conclusions. Because the thickness of the VHE-shell is compatible with emission from a thin rim, particle acceleration in shock waves is likely to be the origin of the γ-ray signal. The measured flux level can be accounted for by inverse Compton emission, but a mixed scenario that includes leptonic and hadronic components and takes into account the ambient matter density inferred from observations also leads to a satisfactory description of the multi-wavelength spectrum. © 2010 ESO.
Keywords: Gamma rays: stars; Supernovae: individual: SN 1006 (G327.6+14.6)

First Fermi-LAT Solar Flare Catalog - Ajello, M.; Baldini, L.; Bastieri, D.; Bellazzini, R.; Berretta, A.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bruel, P.; Buson, S.; Cameron, R. A.; Caputo, R.; et al. (Astrophysical Journal Supplement Series, 2021)
We present the first Fermi-Large Area Telescope (LAT) solar flare catalog covering the 24th solar cycle. This catalog contains 45 Fermi-LAT solar flares (FLSFs) with emission in the gamma-ray energy band (30 MeV-10 GeV) detected with a significance of >= 5 sigma over the years 2010-2018. A subsample containing 37 of these flares exhibits delayed emission beyond the prompt-impulsive hard X-ray phase, with 21 flares showing delayed emission lasting more than two hours. No prompt-impulsive emission is detected in four of these flares. We also present in this catalog observations of GeV emission from three flares originating from active regions located behind the limb of the visible solar disk. We report the lightcurves, spectra, best proton index, and localization (when possible) for all FLSFs. The gamma-ray spectra are consistent with the decay of pions produced by >300 MeV protons. This work contains the largest sample of high-energy gamma-ray flares ever reported and provides a unique opportunity to perform population studies on the different phases of the flare and thus allowing a new window in solar physics to be opened.
CRIS-Team WoS Importer:2021-02-12

First ground-based measurement of atmospheric Cherenkov light from cosmic rays - van Eldik, Christopher; et al. (Physical Review D - Particles, Fields, Gravitation and Cosmology, 2007)
A recently proposed novel technique for the detection of cosmic rays with arrays of Imaging Atmospheric Cherenkov Telescopes is applied to data from the High Energy Stereoscopic System (H.E.S.S.). The method relies on the ground-based detection of Cherenkov light emitted from the primary particle prior to its first interaction in the atmosphere. The charge of the primary particle (Z) can be estimated from the intensity of this light, since it is proportional to Z2. Using H.E.S.S. data, an energy spectrum for cosmic-ray iron nuclei in the energy range 13-200 TeV is derived. The reconstructed spectrum is consistent with previous direct measurements and is one of the most precise so far in this energy range. © 2007 The American Physical Society.

First ground-based measurement of sub-20 GeV to 100 GeV gamma-Rays from the Vela pulsar with HESS II - Abdalla, H.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Arrieta, M.; Backes, Michael; Barnard, M.; Becherini, Y.; Tjus, J. Becker; et al. (Astronomy & Astrophysics, 2018)
Aims. We report on the measurement and investigation of pulsed high-energy y-ray emission from the Vela pulsar, PSR B0833-45, based on observations with the largest telescope of H.E.S.S., CT5, in monoscopic mode, and on data obtained with the Fermi-LAT.
CRIS-Team WoS Importer:2020-01-15
Keywords: Gamma rays: stars; Pulsars: individual: PSR B0833-45; Radiation mechanisms: non-Thermal

First intensity interferometry measurements with the H.E.S.S. telescopes - Zmija, Andreas; Vogel, Naomi; Wohlleben, Frederik; Anton, Gisela; Zink, Adrian; Funk, Stefan (Monthly Notices of the Royal Astronomical Society, 2024)
Intensity interferometry for astrophysical observations has gained increasing interest in the last decade. The method of correlating photon fluxes at different telescopes for high resolution astronomy without access to the phase of the incoming light is insensitive to atmospheric turbulence and does not require high-precision optical path control. The necessary large collection areas can be provided by Imaging Atmospheric Cherenkov Telescopes. Implementation of intensity interferometers to existing telescope systems such as VERITAS and MAGIC has proven to be successful for high-resolution imaging of stars. In 2022 April we equipped two telescopes of the H.E.S.S. array in Namibia with an intensity interferometry setup to measure southern sky stars and star systems during the bright moon period. We mounted an external optical system to the lid of the telescope cameras, which splits the incoming light and feeds it into two photomultipliers in order to measure the zero-baseline correlation within one telescope in addition to the cross-correlation between the telescopes. The optical elements are motorized, which enables live correction of tracking inaccuracies of the telescopes. During the campaign we measured the spatial correlation curves and thereby the angular diameters of λ Sco (Shaula) and σ Sgr (Nunki), while we also performed systematic studies of our interferometer using the multiple star system of α Cru (Acrux).
CRIS-Team Scopus Importer:2024-01-26
Keywords: instrumentation: high angular resolution; instrumentation: interferometers; methods: observational; stars: imaging; techniques: interferometric; telescopes

First limits on the very-high energy gamma-ray afterglow emission of a fast radio burst: H.E.S.S. Observations of FRB 150418 - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Andersson, T.; Anguener, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; et al. (Astronomy & Astrophysics, 2017)
Aims. Following the detection of the fast radio burst FRB150418 by the SUPERB project at the Parkes radio telescope, we aim to search for very-high energy gamma-ray afterglow emission.Methods. Follow-up observations in the very-high energy gamma-ray domain were obtained with the H.E.S.S. imaging atmospheric Cherenkov telescope system within 14.5 h of the radio burst.Results. The obtained 1.4 h of gamma-ray observations are presented and discussed. At the 99% C.L. we obtained an integral upper limit on the gamma-ray flux of Phi(gamma)(E > 350 GeV) < 1.33 x 10(-8) m(-2) s(-1). Differential flux upper limits as function of the photon energy were derived and used to constrain the intrinsic high-energy afterglow emission of FRB 150418.Conclusions. No hints for high-energy afterglow emission of FRB 150418 were found. Taking absorption on the extragalactic background light into account and assuming a distance of z = 0 : 492 based on radio and optical counterpart studies and consistent with the FRB dispersion, we constrain the gamma-ray luminosity at 1 TeV to L < 5 : 1 x 10(47) erg/s at 99% C.L.
Keywords: Astroparticle physics; Gamma rays: general

First results on dark matter annihilation in the Sun using the ANTARES neutrino telescope - Adrian-Martinez, S.; Al Samarai, I.; Albert, A.; Andre, Michel; Anghinolfi, M.; Anton, Gisela; Anton, L.; Anvar, S.; Ardid, Miguel; Astraatmadja, T.; Aubert, J-J.; Baret, B.; et al. (Journal of Cosmology and Astroparticle Physics, 2013)
A search for high-energy neutrinos coming from the direction of the Sun has been performed using the data recorded by the ANTARES neutrino telescope during 2007 and 2008. The neutrino selection criteria have been chosen to maximize the selection of possible signals produced by the self-annihilation of weakly interacting massive particles accumulated in the centre of the Sun with respect to the atmospheric background. After data unblinding, the number of neutrinos observed towards the Sun was found to be compatible with background expectations. The 90% CL upper limits in terms of spin-dependent and spin-independent WIMP-proton cross-sections are derived and compared to predictions of two supersymmetric models, CMSSM and MSSM-7. The ANTARES limits are comparable with those obtained by other neutrino observatories and are more stringent than those obtained by direct search experiments for the spin-dependent WIMP-proton cross-section in the case of hard self-annihilation channels (W+W-, tau(+)tau(-)).
Keywords: neutrino experiments; dark matter detectors; supersymmetry and cosmology; particle physics - cosmology connection

First search for neutrinos in correlation with gamma-ray bursts with the ANTARES neutrino telescope - Adrian-Martinez, S.; Al Samarai, I.; Albert, A.; Andre, Michel; Anghinolfi, M.; Anton, Gisela; Anvar, S.; Ardid, Miguel; Jesus, A. C. Assis; Astraatmadja, T.; Aubert, J-J.; Baret, B.; et al. (Journal of Cosmology and Astroparticle Physics, 2013)
A search for neutrino-induced muons in correlation with a selection of 40 gamma-ray bursts that occurred in 2007 has been performed with the ANTARES neutrino telescope. During that period, the detector consisted of 5 detection lines. The ANTARES neutrino telescope is sensitive to TeV-PeV neutrinos that are predicted from gamma-ray bursts. No events were found in correlation with the prompt photon emission of the gamma-ray bursts and upper limits have been placed on the flux and fluence of neutrinos for different models.
Keywords: neutrino experiments; neutrino astronomy; gamma ray bursts theory

FIRST SEARCH FOR POINT SOURCES OF HIGH-ENERGY COSMIC NEUTRINOS WITH THE ANTARES NEUTRINO TELESCOPE - Adrian-Martinez, S.; Aguilar, J. A.; Al Samarai, I.; Albert, A.; Andre, Michel; Anghinolfi, M.; Anton, Gisela; Anvar, S.; Ardid, Miguel; Jesus, A. C. Assis; Astraatmadja, T.; Aubert, J. -J.; et al. (Astrophysical Journal Letters, 2011)
Results are presented of a search for cosmic sources of high-energy neutrinos with the ANTARES neutrino telescope. The data were collected during 2007 and 2008 using detector configurations containing between 5 and 12 detection lines. The integrated live time of the analyzed data is 304 days. Muon tracks are reconstructed using a likelihood-based algorithm. Studies of the detector timing indicate a median angular resolution of 0.5 +/- 0.1 deg. The neutrino flux sensitivity is 7.5 x 10(-8)(E(v)/GeV)(-2) GeV(-1) s(-1) cm(-2) for the part of the sky that is always visible (delta < -48 deg), which is better than limits obtained by previous experiments. No cosmic neutrino sources have been observed.
Keywords: astroparticle physics; cosmic rays; neutrinos

FlashCam: A fully digital camera for the Cherenkov telescope array medium-sized telescopes - Pühlhofer, G.; Barcelo, M.; Bauer, C.; Bi, B.; Catalano, Jacqueline; Diebold, S.; Eschbach, Stefan; Florin, D.; Foehr, C.; Funk, Stefan; Gadola, A.; Garrecht, F.; et al. (Proceedings of SPIE - The International Society for Optical Engineering, 2019)
FlashCam is an innovative camera designed for the focal plane instrumentation of Cherenkov telescopes. The concept of the FlashCam trigger and readout system is based on the continuous digitization and digital processing of the photo detector signals on FPGAs, and on a high performance, Ethernet-based front-end readout. Because of the modular design, the electronics that have been developed can serve either photomultiplier tubes or silicon-based photon detectors. In the framework of the CTA (Cherenkov telescope array) project, the FlashCam team has developed a PMT-based camera that is suitable for the medium-sized telescopes. With over 100 Cherenkov telescopes, the CTA observatory will run the most sensitive ground-based telescope systems for TeV gamma-ray astronomy when the two arrays in the Northern and Southern Hemisphere (with three different telescope sizes) will go into operation in the upcoming years.
CRIS-Team Scopus Importer:2019-12-31
Keywords: Cherenkov Telescope Array; electronics; gamma-rays; Imaging Atmospheric Cherenkov Telescopes

Flux upper limits for 47 AGN observed with H.E.S.S. in 2004 - 2011 - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2014)
Context. About 40% of the observation time of the High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim of increasing the sample of known extragalactic very-high-energy (VHE, E > 100 GeV) sources and constraining the physical processes at play in potential emitters. Aims. H.E.S.S. observations of AGN, spanning a period from April 2004 to December 2011, are investigated to constrain their γ-ray fluxes. Only the 47 sources without significant excess detected at the position of the targets are presented. Methods. Upper limits on VHE fluxes of the targets were computed and a search for variability was performed on the nightly time scale. Results. For 41 objects, the flux upper limits we derived are the most constraining reported to date. These constraints at VHE are compared with the flux level expected from extrapolations of Fermi-LAT measurements in the two-year catalog of AGN. The H.E.S.S. upper limits are at least a factor of two lower than the extrapolated Fermi-LAT fluxes for 11 objects. Taking into account the attenuation by the extragalactic background light reduces the tension for all but two of them, suggesting intrinsic curvature in the high-energy spectra of these two AGN. Conclusions. Compilation efforts led by current VHE instruments are of critical importance for target-selection strategies before the advent of the Cherenkov Telescope Array (CTA). © ESO, 2014.
Keywords: Galaxies: active; Gamma rays: galaxies

Focus on physics competitions—a résumé concerning submissions in 2020 and an encouragement for future submissions - Fösel, Angela (European Journal of Physics, 2021)
The journal collection 'Focus on Physics Competitions' of the European Journal of Physics (EJP) is an ongoing collection within the European Journal Physics (EJP). In the year 2020, five articles have been submitted within this series. This editorial will briefly sum up the content and ideas of those articles. In addition, the concept of this collection is explained in order to ensure the objectives of this collection are clear and evident for future submissions.<br
Keywords: physics competitions

Follow-up of Astrophysical Transients in Real Time with the IceCube Neutrino Observatory - Aartsen, M. G.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alispach, C.; Amin, N. M.; Andeen, K.; Anderson, T.; Ansseau, I.; et al. (Astrophysical Journal, 2021)
In multi-messenger astronomy, rapid investigation of interesting transients is imperative. As an observatory with a 4 pi steradian field of view, and similar to 99% uptime, the IceCube Neutrino Observatory is a unique facility to follow up transients, as well as to provide valuable insights for other observatories and inform their observational decisions. Since 2016, IceCube has been using low-latency data to rapidly respond to interesting astrophysical events reported by the multi-messenger observational community. Here, we describe the pipeline used to perform these followup analyses, and provide a summary of the 58 analyses performed as of July 2020. We find no significant signal in the first 58 analyses performed. The pipeline has helped inform various electromagnetic observation strategies, and has constrained neutrino emission from potential hadronic cosmic accelerators.
CRIS-Team WoS Importer:2021-04-02

Förderung eines funktionalen Modellverständnisses Lernender in der Quantenphysik - Bitzenbauer, Philipp; Meyn, Jan-Peter (Naturwissenschaftlicher Unterricht und Lehrerbildung im Umbruch? Gesellschaft für Didaktik der Chemie und Physik Jahrestagung 2020, 2021)

Fostering experimental competences of prospective physics teachers - Bitzenbauer, Philipp; Meyn, Jan-Peter (Physics Education, 2021)
Physics teachers are often faced with the challenge of having to set up difficult experiments, or they have to consciously manipulate parameters in order to be able to demonstrate a phenomenon convincingly. Comprehensive laboratory courses are standard procedure in any study program for prospective physics teachers. However, many students, even after completing standard laboratory courses, show difficulties in standard experimental situations, such as measuring an electric current. We report on a new seminar concept for students in physics teacher study programs. This concept is based on the current state of research in physics education, on the teachers' professional competences, and on the modelling of experimental competence, justifying its embedding in teacher training. We present first results of a pilot study carried out to evaluate the seminar.<br
Keywords: experimental competence; teacher education; professional knowledge; assessment

Fostering students' conceptions about the quantum world - results of an interview study - Bitzenbauer, Philipp; Meyn, Jan-Peter (Progress in Science Education, 2021)
Background: Quantum physics is both a highly topical and challenging topic of physics education. Learning quantum physics is inherently difficult because it is unimaginative, counterintuitive and fundamentally different from what learners know from their everyday life and classical physics. The results of recent studies underline that students are often not aware of the relevance of quantum physics and its technologies for their own lives, which makes studying quantum physics even more difficult. This is the starting point of this article: With the Erlanger teaching concept, we present an introductory teaching concept for quantum physics at secondary schools with the aim, among others, to raise students’ awareness of the importance of modern quantum technologies today and in the future. Purpose: In order to evaluate which conceptions about the quantum world arise among students who are introduced to quantum physics with the Erlanger concept, we conducted an interview study. Sample/Setting: A random sample of N = 25 students was interviewed after the intervention (15 male, 10 female) in order to answer the questions mentioned above. The interviews had a duration of 25 – 40 minutes. Prior to the intervention, none of the students had any classroom instruction in quantum physics. Design and Methods: The students’ answers were transcribed and then evaluated on the basis of deductive and inductive categories using qualitative content analysis. The coding was done by independent coders (κ=0.84,95% - CI [0.68;1.00]). Additionally, a cluster analysis was performed and a three-cluster solution was extracted. The three clusters could be interpreted in terms of content and thus facilitate the characterization of occurring types of students’ conceptions after the intervention. Results: After the intervention with our concept, we found elaborated conceptions about the quantum world with the majority of respondents. 11 of the 25 students (cluster 1, labelled Primarily elaborate conception) are aware of the striking differences between quantum and classical physics, as all students in this cluster characterize the quantum world via effects or aspects that do not exist in classical physics. The importance of quantum physics for future technologies was named by the students combined in the cluster 2, labelled Quantum world as the world of technology. 10 of the students interviewed (cluster 3, labelled Quantum world as a classical world on a small scale) seem to stick to their pre-conceptions dominated by classical ways of thinking. Conclusions: Our article provides implications for both classroom practice and future research. For classroom practice, the Erlanger teaching concept serves as a proposal to bridge the gap between quantum physics and the everyday life of the learners. In addition, the results of the interview study presented in this paper make a contribution to the empirical research on students’ conceptions about quantum physics. We not only find individual, independent conceptions of learners, but we also show that there are dependencies between them, allowing us to extract types of conceptions. The extraction of such types of student conceptions for various further concepts of quantum physics will be part of future research and could contribute to our understanding of learning processes in quantum physics. Keywords: quantum physics, interview study, cluster analysis, teaching concept</e
Keywords: quantum physics; teaching concept

Framework and tools for the simulation and analysis of the radio emission from air showers at IceCube - Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alameddine, J. M.; Alves, A. A.; Amin, N. M.; Andeen, K.; Anderson, T.; Anton, Gisela; et al. (Journal of Instrumentation, 2022)
The Surface Enhancement of the IceTop air-shower array will include the addition of radio antennas and scintillator panels, co-located with the existing ice-Cherenkov tanks and covering an area of about 1 km2. Together, these will increase the sensitivity of the IceCube Neutrino Observatory to the electromagnetic and muonic components of cosmic-ray-induced air showers at the South Pole. The inclusion of the radio technique necessitates an expanded set of simulation and analysis tools to explore the radio-frequency emission from air showers in the 70 MHz to 350 MHz band. In this paper we describe the software modules that have been developed to work with time- and frequency-domain information within IceCube's existing software framework, IceTray, which is used by the entire IceCube collaboration. The software includes a method by which air-shower simulation, generated using CoREAS, can be reused via waveform interpolation, thus overcoming a significant computational hurdle in the field.
CRIS-Team Scopus Importer:2022-07-15
Keywords: Antennas; Data analysis; Simulation methods and programs; Software architectures (event data models; frameworks and databases)

Front-end electronics of the Compact High Energy Camera - Leach, S. A.; Lapington, J. S.; Ross, D.; Thornhill, J.; Duffy, C.; Funk, Stefan; Zink, Adrian; Jankowsky, David; White, R.; Zorn, J.; Tibaldo, L.; Varner, G.; et al. (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2019)
The Compact High Energy Camera is a focal plane camera designed for two mirror Schwarzschild–Couder design imaging air Cherenkov telescopes such as the SST-2M variants on the Cherenkov Telescope Array. It utilises a 2048-pixel array of silicon photomultipliers arranged in thirty-two 8 x 8 pixel 2 tiles. Each detector tile is instrumented with a front-end electronics module designed to provide single photon counting with sub-nanosecond timing, full-waveform digitisation and event triggering capabilities based around TARGET ASICs. Performance results including triggering, digitiser noise, signal crosstalk, linearity and dynamic range from initial laboratory tests have been collated and are presented.
CRIS-Team Scopus Importer:2019-05-07
Keywords: CHEC; CTA; Front-end electronics; Full-waveform readout; Readout; Silicon photomultipliers; SST-2M; TARGET

Früh zur Datenkompetenz - Krieger, Michael; Weber, Heiko B.; van Eldik, Christopher (Physik Journal, 2022)

Future GLAST observations of SNRs and PWNe - Funk, Stefan (First GLAST Symposium, 2007)
CRIS-Team WoS Importer:2020-01-15

FV 0 production in p+A collisions at √s=41.6 GeV - Abt, I.; Adams, M.; Agari, M.; Albrecht, H.; Aleksandrov, A.; Amaral, Vasco; Amorim, Antonio; Aplin, S. J.; Aushev, V.; Bagaturia, Y.; Balagura, V.; Bargiotti, M.; et al. (European Physical Journal C, 2009)
Inclusive doubly differential cross sections d σ /dx ∈ dp as a function of Feynman-x (x ) and transverse momentum (p ) for the production of K , Λ and Λ in proton-nucleus interactions at 920 GeV are presented. The measurements were performed by HERA-B in the negative x range (-0.12
Keywords: 13.85.Hd; 14.20.Jn; 14.40.Aq; Inelastic scattering: many-particle final states; Hyperons; pi K and eta mesons

Galactic Cosmic Ray increase associated with an interplanetary magnetic cloud observed by HAWC - Lara, Alejandro; Arunbabu, K. P.; Niembro, Tatiana; Abeysekara, A. U.; Albert, A.; Alfaro, R.; Alvarez, C.; Álvarez, J. D.; Angeles Camacho, J. R.; Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.; et al. (Proceedings of Science, 2022)
We present the observation of an anomalous increment of the galactic cosmic ray (GCR) flux observed by the HAWC array during October 2016. We propose that this anisotropy of the GCR flux was caused by a magnetic flux rope (MFR) i. e., by the helicoidal magnetic field of an interplanetary coronal mass ejection observed at 1 AU at the same time. We computed the trajectory of protons with energy in the range of 10 to 60 GeV, traveling inside the helicoidal magnetic field observed in situ. The direction of these particles changes towards the axis of the MFR resulting in an anisotropy of the GCR flux along this axis. This model shows that the alignment between the MFR axis and the HAWC's asymptotic direction, combined with the high sensitivity of HAWC, allowed us to observe the effect of the passage of the MFR on the GCR flux. We present the HAWC observation associated with the passage of the MFR as well as the heliospheric circumstances around such phenomenon.
CRIS-Team Scopus Importer:2022-12-23

Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei - Breuhaus, M.; Hinton, J. A.; Joshi, Vikas; Reville, B.; Schoorlemmer, H. (Astronomy & Astrophysics, 2022)
We present a study of the expectations for very-high-energy (VHE) to ultra-high-energy (UHE) gamma-ray and neutrino emission from interacting cosmic rays in our Galaxy as well as a comparison to the latest results for the Galactic UHE diffuse emission. We demonstrate the importance of properly accounting for both the mixed cosmic-ray composition and the gamma-ray absorption. We adopt the wounded-nucleon model of nucleus interactions and provide parameterisations of the resulting gamma-ray and neutrino production. Nucleon shielding due to clustering inside nuclei is shown to have a measurable effect on the production of gamma rays and is particularly evident close to breaks and cutoffs in mixed-composition particle spectra. The change in composition around the 'knee' in the cosmic ray spectrum has a noticeable impact on the diffuse neutrino and gamma-ray emission spectra. We show that current and near-future detectors can probe these differences in the key energy range from 10 TeV to 1 PeV, testing the paradigm of the universality of the cosmic ray spectrum and composition throughout the Galaxy.
CRIS-Team WoS Importer:2022-05-20
Keywords: radiation mechanisms: non-thermal; cosmic rays; neutrinos; gamma rays: ISM

Galactic Gamma-Ray Diffuse Emission at TeV Energies with HAWC Data - Alfaro, R.; Alvarez, C.; Arteaga-Velázquez, J. C.; Arunbabu, K. P.; Rojas, D. Avila; Babu, R.; Baghmanyan, V.; Belmont-Moreno, E.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; Carramiñana, A.; et al. (Astrophysical Journal, 2024)
Galactic gamma-ray diffuse emission (GDE) is emitted by cosmic rays (CRs), ultra-relativistic protons, and electrons, interacting with gas and electromagnetic radiation fields in the interstellar medium. Here we present the analysis of teraelectronvolt diffuse emission from a region of the Galactic plane over the range in longitude of l ∈ [43°, 73°], using data collected with the High Altitude Water Cherenkov (HAWC) detector. Spectral, longitudinal, and latitudinal distributions of the teraelectronvolt diffuse emission are shown. The radiation spectrum is compatible with the spectrum of the emission arising from a CR population with an index similar to that of the observed CRs. When comparing with the DRAGON base model, the HAWC GDE flux is higher by about a factor of 2. Unresolved sources such as pulsar wind nebulae and teraelectronvolt halos could explain the excess emission. Finally, deviations of the Galactic CR flux from the locally measured CR flux may additionally explain the difference between the predicted and measured diffuse fluxes.
CRIS-Team Scopus Importer:2024-02-09

Gamma/hadron separation with the HAWC observatory - Alfaro, R.; Alvarez, C.; Álvarez, J. D.; Angeles Camacho, J. R.; Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.; Babu, R.; Belmont-Moreno, E.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; et al. (Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2022)
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory observes atmospheric showers produced by incident gamma rays and cosmic rays with energy from 300 GeV to more than 100 TeV. A crucial phase in analyzing gamma-ray sources using ground-based gamma-ray detectors like HAWC is to identify the showers produced by gamma rays or hadrons. The HAWC observatory records roughly 25,000 events per second, with hadrons representing the vast majority (>99.9%) of these events. The standard gamma/hadron separation technique in HAWC uses a simple rectangular cut involving only two parameters. This work describes the implementation of more sophisticated gamma/hadron separation techniques, via machine learning methods (boosted decision trees and neural networks), and summarizes the resulting improvements in gamma/hadron separation obtained in HAWC.
CRIS-Team Scopus Importer:2022-07-15
Keywords: Crab Nebula; G/H separation; High energy; Machine Learning

Gammapy: A Python package for gamma-ray astronomy - Donath, Axel; Terrier, Régis; Remy, Quentin; Sinha, Atreyee; Nigro, Cosimo; Pintore, Fabio; Khélifi, Bruno; Olivera-Nieto, Laura; Ruiz, Jose Enrique; Brügge, Kai; Linhoff, Maximilian; Contreras, Jose Luis; et al. (Astronomy & Astrophysics, 2023)
Context. Traditionally, TeV-γ-ray astronomy has been conducted by experiments employing proprietary data and analysis software. However, the next generation of γ-ray instruments, such as the Cherenkov Telescope Array Observatory (CTAO), will be operated as open observatories. Alongside the data, they will also make the associated software tools available to a wider community. This necessity prompted the development of open, high-level, astronomical software customized for high-energy astrophysics. Aims. In this article, we present Gammapy, an open-source Python package for the analysis of astronomical γ-ray data, and illustrate the functionalities of its first long-term-support release, version 1.0. Built on the modern Python scientific ecosystem, Gammapy provides a uniform platform for reducing and modeling data from different γ-ray instruments for many analysis scenarios. Gammapy complies with several well-established data conventions in high-energy astrophysics, providing serialized data products that are interoperable with other software packages. Methods. Starting from event lists and instrument response functions, Gammapy provides functionalities to reduce these data by binning them in energy and sky coordinates. Several techniques for background estimation are implemented in the package to handle the residual hadronic background affecting γ-ray instruments. After the data are binned, the flux and morphology of one or more γ-ray sources can be estimated using Poisson maximum likelihood fitting and assuming a variety of spectral, temporal, and spatial models. Estimation of flux points, likelihood profiles, and light curves is also supported. Results. After describing the structure of the package, we show, using publicly available gamma-ray data, the capabilities of Gammapy in multiple traditional and novel γ-ray analysis scenarios, such as spectral and spectro-morphological modeling and estimations of a spectral energy distribution and a light curve. Its flexibility and its power are displayed in a final multi-instrument example, where datasets from different instruments, at different stages of data reduction, are simultaneously fitted with an astrophysical flux model.
CRIS-Team Scopus Importer:2023-11-17
Keywords: Astroparticle physics; Gamma rays: general; Methods: data analysis; Methods: statistical

Gamma-ray blazar spectra with H.E.S.S. II mono analysis: The case of PKS 2155-304 and PG 1553+113 - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Andersson, T.; Anguener, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; et al. (Astronomy & Astrophysics, 2017)
Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment's sensitivity to lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with CT5, providing access to gamma-ray energies below 100 GeV for small zenith angle observations. Such an extension of the instrument's energy range is particularly beneficial for studies of active galactic nuclei with soft spectra, as expected for those at a redshift ≥0.5. The high-frequency peaked BL Lac objects PKS 2155-304 (z = 0:116) and PG 1553+113 (0:43 < z < 0:58) are among the brightest objects in the gamma-ray sky, both showing clear signatures of gamma-ray absorption at E > 100 GeV interpreted as being due to interactions with the extragalactic background light (EBL). Aims. The aims of this work are twofold: to demonstrate the monoscopic analysis of CT5 data with a low energy threshold, and to obtain accurate measurements of the spectral energy distributions (SED) of PKS 2155-304 and PG 1553+113 near their SED peaks at energies 100 GeV. Methods. Multiple observational campaigns of PKS 2155-304 and PG 1553+113 were conducted during 2013 and 2014 using the full H.E.S.S. II instrument (CT1'5). A monoscopic analysis of the data taken with the new CT5 telescope was developed along with an investigation into the systematic uncertainties on the spectral parameters which are derived from this analysis. Results. Using the data from CT5, the energy spectra of PKS 2155-304 and PG 1553+113 were reconstructed down to conservative threshold energies of 80 GeV for PKS 2155-304, which transits near zenith, and 110 GeV for the more northern PG 1553+113. The measured spectra, well fitted in both cases by a log-parabola spectral model (with a 5.0φ statistical preference for non-zero curvature for PKS 2155-304 and 4.5φ for PG 1553+113), were found consistent with spectra derived from contemporaneous Fermi-LAT data, indicating a sharp break in the observed spectra of both sources at E 100 GeV. When corrected for EBL absorption, the intrinsic H.E.S.S. II mono and Fermi-LAT spectrum of PKS 2155-304 was found to show significant curvature. For PG 1553+113, however, no significant detection of curvature in the intrinsic spectrum could be found within statistical and systematic uncertainties.
Keywords: BL Lacertae objects: individual: PG 1553+113; BL Lacertae objects: individual: PKS 2155-304; Galaxies: active; Gamma rays: galaxies

Gamma-Ray Blazars within the First 2 Billion Years - Ackermann, Markus; Ajello, Marco; Baldini, Luca; Ballet, J.; Barbiellini, G.; Bastieri, D.; Gonzalez, J. Becerra; Bellazzini, R.; Bissaldi, Elisabetta; Blandford, R. D.; Bloom, E. D.; Bonino, Raffaella; et al. (Astrophysical Journal Letters, 2017)
The detection of high-redshift (z > 3) blazars enables the study of the evolution of the most luminous relativistic jets over cosmic time. More importantly, high-redshift blazars tend to host massive black holes and can be used to constrain the space density of heavy black holes in the early universe. Here, we report the first detection with the Fermi-Large Area Telescope of five gamma-ray-emitting blazars beyond z. =. 3.1, more distant than any blazars previously detected in.-rays gamma Among these five objects, NVSS J151002+570243 is now the most distant known gamma-ray-emitting blazar at z =. 4.31. These objects have steeply falling gamma-ray spectral energy distributions (SEDs), and. those that have been observed in X-rays have a very hard X-ray spectrum, both typical of powerful blazars. Their Compton dominance ( ratio of the inverse Compton to synchrotron peak luminosities) is also very large (>20). All of these properties place these objects among the most extreme members of the blazar population. Their optical spectra and the modeling of their optical-UV SEDs confirm that these objects harbor massive black holes (MBH similar to 10(8-10) M circle dot 8 10). We find that, at z approximate to 4, the space density of >10(9)M circle dot black holes hosted in radio-loud and radio-quiet active galactic nuclei are similar, implying that radio-loudness may play a key role in rapid black hole growth in the early universe.
CRIS-Team WoS Importer:2020-01-15

Gamma Rays from Fast Black-hole Winds - Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Berretta, A.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bruel, P.; et al. (Astrophysical Journal, 2021)
Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds may be responsible for the observed scaling relation between the masses of the central black holes and the velocity dispersion of stars in galactic bulges. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high energies. In this work we use data from the Fermi Large Area Telescope to search for the gamma-ray emission from galaxies with an ultrafast outflow (UFO): a fast (v similar to 0.1 c), highly ionized outflow, detected in absorption at hard X-rays in several nearby active galactic nuclei (AGN). Adopting a sensitive stacking analysis we are able to detect the average gamma-ray emission from these galaxies and exclude that it is due to processes other than UFOs. Moreover, our analysis shows that the gamma-ray luminosity scales with the AGN bolometric luminosity and that these outflows transfer similar to 0.04% of their mechanical power to gamma-rays. Interpreting the observed gamma-ray emission as produced by cosmic rays (CRs) accelerated at the shock front, we find that the gamma-ray emission may attest to the onset of the wind-host interaction and that these outflows can energize charged particles up to the transition region between galactic and extragalactic CRs.
CRIS-Team WoS Importer:2021-11-26

Gamma rays from the Galactic Centre region: A review - van Eldik, Christopher (Astroparticle Physics, 2015)
Abstract During the last decades, increasingly precise astronomical observations of the Galactic Centre (GC) region at radio, infrared, and X-ray wavelengths laid the foundations to a detailed understanding of the high energy astroparticle physics of this most remarkable location in the Galaxy. Recently, observations of this region in high energy (HE, 10 MeV-100 GeV) and very high energy (VHE, > 100 GeV) γ-rays added important insights to the emerging picture of the Galactic nucleus as a most violent and active region where acceleration of particles to very high energies - possibly up to a PeV - and their transport can be studied in great detail. Moreover, the inner Galaxy is believed to host large concentrations of dark matter (DM), and is therefore one of the prime targets for the indirect search for γ-rays from annihilating or decaying dark matter particles. In this article, the current understanding of the γ-ray emission emanating from the GC is summarised and the results of recent DM searches in HE and VHE γ-rays are reviewed.
Keywords: Dark matter: annihilation; Dark matter: indirect detection; Galaxy: centre; Galaxy: star formation; Gamma rays: observations

Gamma rays from the Galactic Centre region - Su, Meng; van Eldik, Christopher (Comptes Rendus Physique, 2015)
During the last decades, increasingly precise astronomical observations of the Galactic Centre region at radio, infrared, and X-ray wavelengths laid the foundations for a detailed understanding of the high-energy astroparticle physics of this most remarkable location in the Galaxy. Recently, observations of this region in high energy (HE, 10 MeV-100 GeV) and very high energy (VHE, >100 GeV) γ-rays added important insights into the emerging picture of the Galactic nucleus as a most violent and active region where acceleration of particles to highest energies and their transport can be studied in great detail. We review the current understanding of the γ-ray emission emanating from the Galactic Centre.
Keywords: Fermi bubbles; Galactic Centre; Gamma rays; Observations

Gateless patterning of epitaxial graphene by local intercalation - Sorger, Christian; Hertel, Stefan; Jobst, Johannes; Steiner, Christian; Meil, Katharina; Ullmann, Konrad; Albert, A.; Wang, Yabin; Krieger, Michael; Ristein, Jürgen; Maier, Sabine; Weber, Heiko B. (Nanotechnology, 2015)
We present a technique to pattern the charge density of a large-area epitaxial graphene sheet locally without using metallic gates. Instead, local intercalation of the graphene-substrate interface can selectively be established in the vicinity of graphene edges or prede fined voids. It provides changes of the work function of several hundred meV, corresponding to a conversion from n-type to p-type charge carriers. This assignment is supported by photoelectron spectroscopy, scanning tunneling microscopy, scanning electron microscopy and Hall effect measurements. The technique introduces materials contrast to a graphene sheet in a variety of geometries and thus allows for novel experiments and novel functionalities.
UnivIS-Import:2015-04-14:Pub.2015.nat.dphy.IAP.LAP.gatele
Keywords: Graphene; Intercalation; Patterning

GAWBS noise reduction in microstructured fibers - Elser, Dominique Alexander; Korn, Alexander; Lorenz, Stefan; Glöckl, Oliver; Marquardt, Christoph; Andersen, Ulrik Lund; Leuchs, Gerd (2005 European Quantum Electronics Conference, EQEC '05, 2005)
Guided Acoustic Wave Brillouin Scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. We experimentally demonstrate the reduction of GAWBS noise in microstructured fibers in comparison with standard fibers. © 2005 IEEE.
Created from Fastlane, Scopus look-up

Geometrische Eigenschaften der Verschränkungsentropie in der Loop-Quantengravitation - Stritzelberger, Nadine; Sahlmann, Hanno (2014)

Giant gamma-ray bubbles in the Milky Way - Franckowiak, Anna; Funk, Stefan (Physics Today, 2014)

Gibt es die mechanische Analogie zum Schwingkreis? - Meyn, Jan-Peter (Stolpersteine überwinden im Physikunterricht - Anregung zu fachgerechten Elementarisierungen, 2018)
Keywords: Schwingkreis

GiBUU based neutrino interaction simulations in KM3NeT - Schumann, Johannes; Jung, B. (Journal of Instrumentation, 2021)
The simulation of the neutrino interaction is a crucial step in the simulation chain of a neutrino experiment. The different processes taking part in the neutrino scattering on a nucleus require several approximations in order to make the simulation possible and to realize reasonable computation times. This can be realised in different ways, e.g. by parametrised models for the different scattering processes and energy regimes as it is implemented in GENIE. The GiBUU neutrino generator utilises the Boltzmann-Uehling-Uhlenbeck equation to simulate the particle flow after the neutrino interactions, the so-called final state interactions. The detector-specific results in form of the visible energy in the detector after the light propagation simulation and the KM3NeT event reconstruction are presented. In addition to that, the comparison to the GENIE based simulation environment in KM3NeT (gSeaGen) is drawn.
CRIS-Team Scopus Importer:2021-10-08
Keywords: Neutrino detectors; Simulation methods and programs

GLAST and ground-based gamma-ray astronomy - Funk, Stefan; et al. (First GLAST Symposium, 2007)
CRIS-Team WoS Importer:2020-01-15

Graphitization of polymer surfaces by low-energy ion irradiation - Lazareva, Irina; Koval, Yury; Alam, Sahabul; Strömsdörfer, Stephan; Müller, Paul (Applied Physics Letters, 2007)
The surface of several polymers was graphitized by low-energy ion irradiation. Their conducting properties were studied as a function of the energy of the ions and the irradiation temperature. It was found that at rather modest ion energies (∼1000 eV) and irradiation temperatures (<400 °C), polymer surfaces transform to a graphitized state. The graphitized layer consists of overlapping graphite islands with a diameter of 1-3 nm and exhibits a semimetallic conductivity. Gradually reducing the energy of the ions and the irradiation temperature, the authors observed a transition from semimetallic to variable range hopping conductivity. © 2007 American Institute of Physics.

Graph Neural Networks for low-energy event classification & reconstruction in IceCube - Abbasi, R.; Ackermann, M.; Adams, J.; Aggarwal, N.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alameddine, J. M.; Alves Jr, A. A.; Amin, N. M.; Andeen, K.; Anderson, T.; et al. (Journal of Instrumentation, 2022)
IceCube, a cubic-kilometer array of optical sensors built to detect atmospheric and astrophysical neutrinos between 1 GeV and 1 PeV, is deployed 1.45 km to 2.45 km below the surface of the ice sheet at the South Pole. The classification and reconstruction of events from the in-ice detectors play a central role in the analysis of data from IceCube. Reconstructing and classifying events is a challenge due to the irregular detector geometry, inhomogeneous scattering and absorption of light in the ice and, below 100 GeV, the relatively low number of signal photons produced per event. To address this challenge, it is possible to represent IceCube events as point cloud graphs and use a Graph Neural Network (GNN) as the classification and reconstruction method. The GNN is capable of distinguishing neutrino events from cosmic-ray backgrounds, classifying different neutrino event types, and reconstructing the deposited energy, direction and interaction vertex. Based on simulation, we provide a comparison in the 1 GeV-100 GeV energy range to the current state-of-the-art maximum likelihood techniques used in current IceCube analyses, including the effects of known systematic uncertainties. For neutrino event classification, the GNN increases the signal efficiency by 18% at a fixed background rate, compared to current IceCube methods. Alternatively, the GNN offers a reduction of the background (i.e. false positive) rate by over a factor 8 (to below half a percent) at a fixed signal efficiency. For the reconstruction of energy, direction, and interaction vertex, the resolution improves by an average of 13%-20% compared to current maximum likelihood techniques in the energy range of 1 GeV-30 GeV. The GNN, when run on a GPU, is capable of processing IceCube events at a rate nearly double of the median IceCube trigger rate of 2.7 kHz, which opens the possibility of using low energy neutrinos in online searches for transient events.
CRIS-Team WoS Importer:2023-02-17

Graph neural networks for reconstruction and classification in KM3NeT - Reck, Stefan; Guderian, D.; Vermarien, G.; Domi, A. (Journal of Instrumentation, 2021)
KM3NeT, a neutrino telescope currently under construction in the Mediterranean Sea, consists of a network of large-volume Cherenkov detectors. Its two different sites, ORCA and ARCA, are optimised for few GeV and TeV-PeV neutrino energies, respectively. This allows for studying a wide range of physics topics spanning from the determination of the neutrino mass hierarchy to the detection of neutrinos from astrophysical sources. Deep learning techniques provide promising methods to analyse the signatures induced by charged particles traversing the detector. This document will cover a deep learning based approach using graph convolutional networks to classify and reconstruct events in both the ORCA and ARCA detector. Performance studies on simulations as well as applications to real data will be presented, together with comparisons to classical approaches.
CRIS-Team Scopus Importer:2021-11-26
Keywords: Cherenkov detectors; Data analysis; Neutrino detectors; Pattern recognition; cluster finding; calibration and fitting methods

Ground- and Space-Based Gamma-Ray Astronomy - Funk, Stefan (Annual Review of Nuclear and Particle Science, 2015)
Keywords: Cosmic rays; Dark matter; Fermi-LAT; Galactic center; Imaging atmospheric Cherenkov telescopes; γ-ray astronomy

Growth of two-dimensional dodecagonal colloidal quasicrystals: Particles with isotropic pair interactions with two length scales vs. patchy colloids with preferred binding angles - Gemeinhardt, Anja; Martinsons, Miriam; Schmiedeberg, Michael (European Physical Journal E, 2018)

Grundlegende Experimentiertechnik im Physikunterricht - Meyn, Jan-Peter (Oldenbourg, 2011)

Grundlegende Experimentiertechnik im Physikunterricht - Meyn, Jan-Peter (Oldenbourg Wissenschaftsverlag, 2013)
UnivIS-Import:2015-04-02:Pub.2011.nat.dphy.PI.PDP.grundl

gSeaGen: The KM3NeT GENIE-based code for neutrino telescopes - Aiello, S.; Kalekin, Oleg; Domi, Alba; Albert, A.; Garre, S. Alves; Aly, Z.; Ameli, F.; Andre, M.; Androulakis, G.; Anghinolfi, M.; Anguita, M.; Anton, G.; et al. (Computer Physics Communications, 2020)
The gSeaGen code is a GENIE-based application developed to efficiently generate high statistics samples of events, induced by neutrino interactions, detectable in a neutrino telescope. The gSeaGen code is able to generate events induced by all neutrino flavours, considering topological differences between track-type and shower-like events. Neutrino interactions are simulated taking into account the density and the composition of the media surrounding the detector. The main features of gSeaGen are presented together with some examples of its application within the KM3NeT project. Program summary: Program Title: gSeaGen CPC Library link to program files: http://dx.doi.org/10.17632/ymgxvy2br4.1 Licensing provisions: GPLv3 Programming language: C++ External routines/libraries: GENIE [1] and its external dependencies. Linkable to MUSIC [2] and PROPOSAL [3]. Nature of problem: Development of a code to generate detectable events in neutrino telescopes, using modern and maintained neutrino interaction simulation libraries which include the state-of-the-art physics models. The default application is the simulation of neutrino interactions within KM3NeT [4]. Solution method: Neutrino interactions are simulated using GENIE, a modern framework for Monte Carlo event generators. The GENIE framework, used by nearly all modern neutrino experiments, is considered as a reference code within the neutrino community. Additional comments including restrictions and unusual features: The code was tested with GENIE version 2.12.10 and it is linkable with release series 3. Presently valid up to 5 TeV. This limitation is not intrinsic to the code but due to the present GENIE valid energy range. References: [1] C. Andreopoulos at al., Nucl. Instrum. Meth. A614 (2010) 87. [2] P. Antonioli et al., Astropart. Phys. 7 (1997) 357. [3] J. H. Koehne et al., Comput. Phys. Commun. 184 (2013) 2070. [4] S. Adrián-Martínez et al., J. Phys. G: Nucl. Part. Phys. 43 (2016) 084001.
CRIS-Team Scopus Importer:2020-07-17
Keywords: Astroparticle physics; GENIE; High energy neutrinos; KM3NeT; Monte Carlo event generator; Neutrino oscillations; Neutrino telescopes

Hadronic re-acceleration at the Crab pulsar wind termination shock as a source of PeV gamma-rays - Spencer, Samuel; Mitchell, Alison; Reville, Brian (38th International Cosmic Ray Conference (ICRC2023), 2023)
Recent results from LHAASO and Tibet ASγ suggest that the Crab Nebula’s gamma-ray spectrum extends to the PeV energy range, however the production mechanisms of this highest energy emission remain unclear. It has been postulated that a secondary component of hadronic emission could explain the highest energy gamma-ray flux points, however the origin and acceleration mechanism for this hadronic population has yet to be explained. We postulate one scenario in which hadrons diffuse over time into the Crab pulsar wind nebula from the surrounding supernova ejecta, and are subsequently re-accelerated by the pulsar wind termination shock. We present results of direct particle transport simulations (including radial evolution) to determine if this scenario is viable over the lifetime of the Crab system.<br

Halo fraction in TeV-bright pulsar wind nebulae - Giacinti, G.; Mitchell, Alison M. W.; Lopez-Coto, R.; Joshi, Vikas; Parsons, R. D.; Hinton, J. A. (Astronomy & Astrophysics, 2020)
The discovery of extended TeV emission around the Geminga and PSR B0656+14 pulsars, with properties consistent with free particle propagation in the interstellar medium (ISM), has led to the suggestion of "TeV halos" as a separate source class, which is distinct from pulsar wind nebulae. This has sparked considerable discussion on the possible presence of such halos in other systems. In defining halos as regions where the pulsar no longer dominates the dynamics of the interstellar medium, yet where an over-density of relativistic electrons is present, we make an assessment of the current TeV source population associated with energetic pulsars in terms of size and estimated energy density. Based on two alternative estimators, we conclude that a large majority of the known TeV sources have emission originating in the zone that is energetically and dynamically dominated by the pulsar (i.e. the pulsar wind nebula), rather than from a surrounding halo of escaped particles diffusing into the ISM. Furthermore, whilst the number of established halos will surely increase in the future since there is a known large population of older, less energetic pulsars, we find that it is unlikely that such halos contribute significantly to the total TeV gamma -ray luminosity from electrons accelerated in pulsar wind nebulae due to their lower intrinsic surface brightness.
CRIS-Team WoS Importer:2020-05-19
Keywords: Pulsars: general; Diffusion; Gamma rays: general; Cosmic rays

Hard and bright gamma-ray emission at the base of the Fermi bubbles - Herold, Laura; Malyshev, Dmitry (Astronomy & Astrophysics, 2019)
Context. The Fermi bubbles (FBs) are large gamma-ray emitting lobes extending up to 55◦ in latitude above and below the Galactic center (GC). Although the FBs were discovered eight years ago, their origin and the nature of the gamma-ray emission are still unresolved. Understanding the properties of the FBs near the Galactic plane may provide a clue to their origin. Previous analyses of the gamma-ray emission at the base of the FBs, what remains after subtraction of Galactic foregrounds, have shown an increased intensity compared to the FBs at high latitudes, a hard power-law spectrum without evidence of a cutoff up to approximately 1 TeV, and a displacement of the emission to negative longitudes relative to the GC. Aims. We analyze nine years of Fermi Large Area Telescope data in order to study in more detail than the previous analyses the gamma-ray emission at the base of the FBs, especially at energies above 10 GeV. Methods. We used a template analysis method to model the observed gamma-ray data and calculate the residual emission after subtraction of the expected foreground and background emission components. Since there are large uncertainties in the determination of the Galactic gamma-ray emission toward the GC, we used several methods to derive Galactic gamma-ray diffuse emission and the contribution from point sources to estimate the uncertainties in the emission at the base of the FBs. Results. We confirm that the gamma-ray emission at the base of the FBs is well described by a simple power law up to 1 TeV energies. The 95% confidence lower limit on the cutoff energy is about 500 GeV. It has larger intensity than the FBs emission at high latitudes and is shifted to the west (negative longitudes) from the GC. If the emission at the base of the FBs is indeed connected to the high-latitude FBs, then the shift of the emission to negative longitudes disfavors models in which the FBs are created by the supermassive black hole at the GC. We find that the gamma-ray spectrum can be explained either by gamma rays produced in hadronic interactions or by leptonic inverse Compton scattering. In the hadronic scenario, the emission at the base of the FBs can be explained either by several hundred supernova remnants (SNRs) near the GC or by about ten SNRs at a distance of ∼1 kpc. In the leptonic scenario, the necessary number of SNRs that can produce the required density of CR electrons is a factor of a few larger than in the hadronic scenario.
CRIS-Team Scopus Importer:2021-04-20
Keywords: Astroparticle physics; Galaxy: bulge; Galaxy: center; Gamma rays: diffuse background; ISM: bubbles; ISM: jets and outflows

HAWC and Fermi-LAT Detection of Extended Emission from the Unidentified Source 2HWC J2006+341 - Albert, A.; Alfaro, R.; Alvarez, C.; Angeles Camacho, J. R.; Araya, M.; Arteaga-Velazquez, J. C.; Arunbabu, K. P.; Avila Rojas, D.; Ayala Solares, H. A.; Baghmanyan, V.; Belmont-Moreno, E.; Brisbois, C.; et al. (Astrophysical Journal Letters, 2020)
The discovery of the TeV point source 2HWC J2006+341 was reported in the second HAWC gamma-ray catalog. We present a follow-up study of this source here. The TeV emission is best described by an extended source with a soft spectrum. At GeV energies, an extended source is significantly detected in Fermi-LAT data. The matching locations, sizes, and spectra suggest that both gamma-ray detections correspond to the same source. Different scenarios for the origin of the emission are considered and we rule out an association to the pulsar PSR J2004 +3429 due to extreme energetics required, if located at a distance of 10.8 kpc.
CRIS-Team Scopus Importer:2020-11-20

HAWC as a Ground-Based Space-Weather Observatory - Alvarez, C.; Angeles Camacho, J. R.; Arteaga-Velázquez, J. C.; Arunbabu, K. P.; Avila Rojas, D.; Baghmanyan, V.; Belmont-Moreno, E.; BenZvi, S. Y.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; Colín-Farias, P.; et al. (Solar Physics, 2021)
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is located close to the equator (latitude 18 ∘ N), at an altitude of 4100 m above sea level. HAWC has 295 water Cherenkov detectors (WCD), each containing four photomultiplier tubes (PMT). The main purpose of HAWC is the determination of the energy and arrival direction of very high energy gamma rays produced by energetic processes in the universe, HAWC also has a scaler system which counts the arrival of secondary particles to the detector. In this work we show that the scaler system of HAWC is an ideal instrument for solar modulation and space-weather studies due to its large area and high sensitivity. In order to prepare the scaler system for low energy heliospheric studies, we model and correct the efficiency variation of each PMT of the array, which result in a capability to measure variations > 0.01 % with high accuracy. Using the singular value decomposition method, we correct the rate deviations of all PMTs of the array, due to changes in efficiency, gain and operational voltage. We isolate and remove the atmospheric modulations of the PMTs count rates measured by the TDC-scaler data acquisition system. In particular, the atmospheric pressure at the HAWC site exhibits an oscillating behavior with a period of ∼12 hours and we make use of this periodic property to estimate the pressure coefficients for the HAWC TDC-scaler system. These corrections performed on the TDC-scaler system make the HAWC TDC-scaler system an ideal instrument for solar modulation and space-weather studies. As examples of this capability, we present the preliminary analysis of the solar modulation of cosmic rays at three time scales observed by HAWC, with an unprecedented accuracy.
CRIS-Team Scopus Importer:2021-06-18
Keywords: Atmospheric pressure modulation; Cosmic rays; Fast Fourier transform; Solar modulation

HAWC Detection of a TeV Halo Candidate Surrounding a Radio-quiet Pulsar - Albert, A.; Alfaro, R.; Arteaga-Velázquez, J. C.; Ayala Solares, H. A.; Belmont-Moreno, E.; Capistrán, T.; Carramiñana, A.; Casanova, S.; Cotzomi, J.; De León, S. Coutiño; Fuente, E. De la; de León, C.; et al. (Astrophysical Journal Letters, 2023)
Extended very-high-energy (VHE; 0.1-100 TeV) γ-ray emission has been observed around several middle-aged pulsars and referred to as “TeV halos.” Their formation mechanism remains under debate. It is also unknown whether they are ubiquitous or related to a certain subgroup of pulsars. With 2321 days of observation, the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory detected VHE γ-ray emission at the location of the radio-quiet pulsar PSR J0359+5414 with >6σ significance. By performing likelihood tests with different spectral and spatial models and comparing the TeV spectrum with multiwavelength observations of nearby sources, we show that this excess is consistent with a TeV halo associated with PSR J0359+5414, though future observation of HAWC and multiwavelength follow-ups are needed to confirm this nature. This new halo candidate is located in a noncrowded region in the outer galaxy. It shares similar properties to the other halos but its pulsar is younger and radio-quiet. Our observation implies that TeV halos could commonly exist around pulsars and their formation does not depend on the configuration of the pulsar magnetosphere.
CRIS-Team Scopus Importer:2023-03-03

HAWC J2227+610 and Its Association with G106.3+2.7, a New Potential Galactic PeVatron - Albert, A.; Alfaro, R.; Alvarez, C.; Angeles Camacho, J. R.; Arteaga-Velazquez, J. C.; Arunbabu, K. P.; Avila Rojas, D.; Ayala Solares, H. A.; Baghmanyan, V.; Belmont-Moreno, E.; Benzvi, S. Y.; Brisbois, C.; et al. (Astrophysical Journal Letters, 2020)
We present the detection of very-high-energy gamma-ray emission above 100 TeV from HAWC J2227+610 with the High-Altitude Water Cherenov Gamma-Ray Observatory (HAWC) observatory. Combining our observations with previously published results by the Very Energetic Radiation Imaging Telescope Array System (VERTIAS), we interpret the gamma-ray emission from HAWC J2227+610 as emission from protons with a lower limit in their cutoff energy of 800 TeV. The most likely source of the protons is the associated supernova remnant G106.3+2.7, making it a good candidate for a Galactic PeVatron. However, a purely leptonic origin of the observed emission cannot be excluded at this time.
CRIS-Team Scopus Importer:2020-07-10

HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon - Abeysekara, A. U.; Albert, A.; Alfaro, R.; Alvarez, C.; Camacho, J. R.Angeles; Arteaga-Velázquez, J. C.; Arunbabu, K. P.; Rojas, D. Avila; Solares, H. A.Ayala; Baghmanyan, V.; Belmont-Moreno, E.; BenZvi, S. Y.; et al. (Nature Astronomy, 2021)
Cosmic rays with energies up to a few PeV are known to be accelerated within the Milky Way1,2. Traditionally, it has been presumed that supernova remnants were the main source of these very-high-energy cosmic rays3,4, but theoretically it is difficult to accelerate protons to PeV energies5,6 and observationally there simply is no evidence of the remnants being sources of hadrons with energies above a few tens of TeV7,8. One possible source of protons with those energies is the Galactic Centre region9. Here, we report observations of 1–100 TeV γ rays coming from the ‘Cygnus Cocoon’10, which is a superbubble that surrounds a region of massive star formation. These γ rays are likely produced by 10–1,000 TeV freshly accelerated cosmic rays that originate from the enclosed star-forming region Cyg OB2. Until now it was not known that such regions could accelerate particles to these energies. The measured flux likely originates from hadronic interactions. The spectral shape and the emission profile of the Cocoon changes from GeV to TeV energies, which reveals the transport of cosmic particles and historical activity in the superbubble.
CRIS-Team Scopus Importer:2021-04-02

HAWC Search for High-mass Microquasars - Albert, A.; Alfaro, R.; Alvarez, C.; Angeles Camacho, J. R.; Arteaga-Velazquez, J. C.; Arunbabu, K. P.; Avila Rojas, D.; Ayala Solares, H. A.; Baghmanyan, V.; Belmont-Moreno, E.; Benzvi, S. Y.; Brisbois, C.; et al. (Astrophysical Journal Letters, 2021)
Microquasars with high-mass companion stars are promising very high energy (VHE; 0.1-100 TeV) gamma-ray emitters, but their behaviors above 10 TeV are poorly known. Using the High Altitude Water Cerenkov (HAWC) observatory, we search for excess gamma-ray emission coincident with the positions of known high-mass microquasars (HMMQs). No significant emission is observed for LS 5039, Cyg X-1, Cyg X-3, and SS 433 with 1523 days of HAWC data. We set the most stringent limit above 10 TeV obtained to date on each individual source. Under the assumption that HMMQs produce gamma rays via a common mechanism, we have performed source-stacking searches, considering two different scenarios: (I) gamma-ray luminosity is a fraction epsilon ( gamma ) of the microquasar jet luminosity, and (II) VHE gamma rays are produced by relativistic electrons upscattering the radiation field of the companion star in a magnetic field B. We obtain epsilon ( gamma ) < 5.4 x 10(-6) for scenario I, which tightly constrains models that suggest observable high-energy neutrino emission by HMMQs. In the case of scenario II, the nondetection of VHE gamma rays yields a strong magnetic field, which challenges synchrotron radiation as the dominant mechanism of the microquasar emission between 10 keV and 10 MeV.
CRIS-Team WoS Importer:2021-05-21

HAWC Study of the Ultra-high-energy Spectrum of MGRO J1908+06 - Albert, A.; Alfaro, R.; Alvarez, C.; Alvarez, J. D.; Angeles Camacho, J. R.; Arteaga-Velazquez, J. C.; Avila Rojas, D.; Solares, H. A. Ayala; Babu, R.; Belmont-Moreno, E.; Brisbois, C.; Caballero-Mora, K. S.; et al. (Astrophysical Journal, 2022)
We report TeV gamma-ray observations of the ultra-high-energy source MGRO J1908+06 using data from the High Altitude Water Cherenkov Observatory. This source is one of the highest-energy known gamma-ray sources, with emission extending past 200 TeV. Modeling suggests that the bulk of the TeV gamma-ray emission is leptonic in nature, driven by the energetic radio-faint pulsar PSR J1907+0602. Depending on what assumptions are included in the model, a hadronic component may also be allowed. Using the results of the modeling, we discuss implications for detection prospects by multi-messenger campaigns.
CRIS-Team WoS Importer:2022-04-22
Keywords: Gamma-ray sources; Gamma-rays; Pulsars; Supernova remnants; Gamma-ray astronomy

HAWC Study of the Very-high-energy γ-Ray Spectrum of HAWC J1844−034 - Albert, A.; Alvarez, C.; Rojas, D. Avila; Solares, H. A.Ayala; Babu, R.; Belmont-Moreno, E.; Breuhaus, M.; Capistrán, T.; Carramiñana, A.; Casanova, S.; Cotzomi, J.; de León, S. Coutiño; et al. (Astrophysical Journal, 2023)
Recently, the region surrounding eHWC J1842−035 has been studied extensively by γ-ray observatories due to its extended emission reaching up to a few hundred TeV and potential as a hadronic accelerator. In this work, we use 1910 days of cumulative data from the High Altitude Water Cherenkov (HAWC) observatory to carry out a dedicated systematic source search of the eHWC J1842−035 region. During the search, we found three sources in the region, namely, HAWC J1844−034, HAWC J1843−032, and HAWC J1846−025. We have identified HAWC J1844−034 as the extended source that emits photons with energies up to 175 TeV. We compute the spectrum for HAWC J1844−034, and by comparing with the observational results from other experiments, we have identified HESS J1843−033, LHAASO J1843−0338, and TASG J1844−038 as very-high-energy γ-ray sources with a matching origin. Also, we present and use the multiwavelength data to fit the hadronic and leptonic particle spectra. We have identified four pulsar candidates in the nearby region in which PSR J1844−0346 is found to be the most likely candidate due to its proximity to HAWC J1844−034 and the computed energy budget. We have also found SNR G28.6−0.1 as a potential counterpart source of HAWC J1844−034 for which both leptonic and hadronic scenarios are feasible.
CRIS-Team Scopus Importer:2023-09-22

HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312-423 - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Monthly Notices of the Royal Astronomical Society, 2013)
A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ-rays from the blazar 1ES 1312-423, 2° away from the radio galaxy. With a differential flux at 1 TeV of f(1 TeV) = (1.9 ± 0.6 ± 0.4) × 10 cm s TeV corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index γ = 2.9 ± 0.5 ± 0.2, 1ES 1312-423 is one of the faintest sources ever detected in the very high energy (E <100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (100 < E MeV) of a hard spectrum (γ =1.4±0.4stat ±0.2sys) source coincident with 1ES 1312-423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
Keywords: Bl Lacertae objects: individual: 1ES 1312-423; Galaxies: active; Galaxies: jets; Gamma-rays: galaxies.; Radiation mechanisms: non-thermal

HESS and Fermi-LAT observations of PSR B1259-63/LS 2883 during its 2014 and 2017 periastron passages - Abdalla, H.; Adam, R.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Ashkar, H.; Backes, M.; Martins, V. Barbosa; Barnard, M.; et al. (Astronomy & Astrophysics, 2020)
Context. PSR B1259-63/LS 2883 is a gamma-ray binary system consisting of a pulsar in an eccentric orbit around a bright Oe stellar-type companion star that features a dense circumstellar disc. The bright broad-band emission observed at phases close to periastron offers a unique opportunity to study particle acceleration and radiation processes in binary systems. Observations at gamma-ray energies constrain these processes through variability and spectral characterisation studies.
CRIS-Team WoS Importer:2020-01-31
Keywords: Pulsars: general; Radiation mechanisms: non-thermal; Shock waves; γ-rays: general; Binaries: general; Astroparticle physics

HESS and Suzaku observations of the Vela X pulsar wind nebula - Abdalla, H.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Backes, M.; Barnard, M.; Becherini, Y.; Berge, D.; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2019)
Context. Pulsar wind nebulae (PWNe) represent the most prominent population of Galactic very-high-energy gamma-ray sources and are thought to be an efficient source of leptonic cosmic rays. Vela X is a nearby middle-aged PWN, which shows bright X-ray and TeV gamma-ray emission towards an elongated structure called the cocoon.
CRIS-Team WoS Importer:2019-07-23
Keywords: Gamma rays: stars; Pulsars: individual: PSR B0833-45; Radiation mechanisms: non-thermal; Stars: winds; outflows; Acceleration of particles

H.E.S.S. constraints on dark matter annihilations towards the sculptor and carina dwarf galaxies - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Barnacka, A.; Barres De Almeida, U.; Bazer-Bachi, A. R.; Becherini, Y.; Becker, J.; Behera, B.; Bernlöhr, K.; et al. (Astroparticle Physics, 2011)
The Sculptor and Carina dwarf spheroidal galaxies were observed with the H.E.S.S. Cherenkov telescope array between January 2008 and December 2009. The data sets consist of a total of 11.8 h and 14.8 h of high quality data, respectively. No gamma-ray signal was detected at the nominal positions of these galaxies above 220 GeV and 320 GeV, respectively. Upper limits on the gamma-ray fluxes at 95% CL assuming two forms for the spectral energy distribution (a power law shape and one derived from dark matter annihilation) are obtained at the level of 10-10 cm s in the TeV range. Constraints on the velocity weighted dark matter particle annihilation cross section for both Sculptor and Carina dwarf galaxies range from 〈σv〉 ∼ 10 cm s down to 〈σv〉 ∼ 10 cm s depending on the dark matter halo model used. Possible enhancements of the gamma-ray flux are studied: the Sommerfeld effect, which is found to exclude some dark matter particle masses, the internal Bremsstrahlung and clumps in the dark-matter halo distributions. © 2011 Published by Elsevier B.V.
Keywords: Carina; Dark matter; Gamma-rays: observations - Dwarf spheroidal galaxy; Internal Bremsstrahlung; Sculptor; Sommerfeld enhancement

H.E.S.S. detection of TeV emission from the interaction region between the supernova remnant G349.7+0.2 and a molecular cloud - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguner, E. O.; Backes, Michael; Balenderans, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; et al. (Astronomy & Astrophysics, 2015)
G349.7+0.2 is a young Galactic supernova remnant (SNR) located at the distance of 11.5 kpc and observed across the entire electromagnetic spectrum from radio to high energy (HE; 0.1 GeV < E < 100 GeV) γ-rays. Radio and infrared observations indicate that the remnant is interacting with a molecular cloud. In this paper, the detection of very high energy (VHE, E > 100 GeV) γ-ray emission coincident with this SNR with the High Energy Stereoscopic System (H.E.S.S.) is reported. This makes it one of the farthest Galactic SNR ever detected in this domain. An integral flux F (E > 400 GeV) = (6.5 ± 1.1 ± 1.3) × 10 ph cm s corresponding to ∼0.7% of that of the Crab Nebula and to a luminosity of ∼10 erg s above the same energy threshold, and a steep photon index Γ = 2.8 ± 0.27stat ± 0.20 are measured. The analysis of more than 5 yr of Fermi-LAT data towards this source shows a power-law like spectrum with a best-fit photon index Γ = 2.2 ± 0.04 . The combined γ-ray spectrum of G349.7+0.2 can be described by either a broken power-law (BPL) or a power-law with exponential (or sub-exponential) cutoff(PLC). In the former case, the photon break energy is found at E = 55 GeV, slightly higher than what is usually observed in the HE/VHE γ-ray emitting middle-aged SNRs known to be interacting with molecular clouds. In the latter case, the exponential (respectively sub-exponential) cutoff energy is measured at E = 1.4 (respectively 0.35 ) TeV. A pion-decay process resulting from the interaction of the accelerated protons and nuclei with the dense surrounding medium is clearly the preferred scenario to explain the γ-ray emission. The BPL with a spectral steepening of 0.5-1 and the PLC provide equally good fits to the data. The product of the average gas density and the total energy content of accelerated protons and nuclei amounts to n W ∼ 5 × 10 erg cm.
Keywords: Gamma rays: General; ISM: clouds; ISM: supernova remnants

HESS detection of very high-energy gamma-ray emission from the quasar PKS 0736+017 - Abdalla, H.; Adam, R.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Ashkar, H.; Backes, M.; Martins, V. Barbosa; Barnard, M.; et al. (Astronomy & Astrophysics, 2020)
Context. Flat-spectrum radio-quasars (FSRQs) are rarely detected at very high energies (E& x2004;>=& x2004;100 GeV) due to their low-frequency-peaked spectral energy distributions. At present, only six FSRQs are known to emit very high-energy (VHE) photons, representing only 7% of the VHE extragalactic catalog, which is largely dominated by high-frequency-peaked BL Lacertae objects. Aims. Following the detection of MeV-GeV gamma-ray flaring activity from the FSRQ PKS 0736+017 (z& x2004;=& x2004;0.189) with Fermi-LAT, the H.E.S.S. array of Cherenkov telescopes triggered target-of-opportunity (ToO) observations on February 18, 2015, with the goal of studying the gamma-ray emission in the VHE band. Methods. H.E.S.S. ToO observations were carried out during the nights of February 18, 19, 21, and 24, 2015. Together with Fermi-LAT, the multi-wavelength coverage of the flare includes Swift observations in soft X-ray and optical-UV bands, and optical monitoring (photometry and spectro-polarimetry) by the Steward Observatory, and the ATOM, the KAIT, and the ASAS-SN telescopes. Results. VHE emission from PKS 0736+017 was detected with H.E.S.S. only during the night of February 19, 2015. Fermi-LAT data indicate the presence of a gamma-ray flare, peaking at the time of the H.E.S.S. detection, with a flux doubling timescale of around six hours. The gamma-ray flare was accompanied by at least a 1 mag brightening of the non-thermal optical continuum. No simultaneous observations at longer wavelengths are available for the night of the H.E.S.S. detection. The gamma-ray observations with H.E.S.S. and Fermi-LAT are used to put constraints on the location of the gamma-ray emitting region during the flare: it is constrained to be just outside the radius of the broad-line region r(BLR) with a bulk Lorentz factor Gamma& x2004;similar or equal to& x2004;20, or at the level of the radius of the dusty torus r(torus) with Gamma& x2004;similar or equal to& x2004;60. Conclusions. PKS 0736+017 is the seventh FSRQ known to emit VHE photons, and at z& x2004;=& x2004;0.189 is the nearest so far. The location of the gamma-ray emitting region during the flare can be tightly constrained thanks to opacity, variability, and collimation arguments.
CRIS-Team WoS Importer:2020-02-18
Keywords: Astroparticle physics; Gamma rays: general; Quasars: individual: PKS 0736+017; Relativistic processes

HESS discovery of very high energy gamma-ray emission from PKS 0625-354 - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Andersson, T.; Anguner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; et al. (Monthly Notices of the Royal Astronomical Society, 2018)
PKS 0625-354 (z = 0.055) was observed with the four High Energy Stereoscopic System (H.E.S.S.) telescopes in 2012 during 5.5 h. The source was detected above an energy threshold of 200 GeV at a significance level of 6.1 sigma. No significant variability is found in these observations. The source is well described with a power-law spectrum with photon index Gamma = 2.84 +/- 0.50(stat) +/- 0.10(syst) and normalization (at E-0 = 1.0 TeV) N-0(E-0)=(0.58 +/- 0.22(stat) +/- 0.12(syst)) x 10(-12) TeV-1 cm(-2) s(-1). Multiwavelength data collected with Fermi-LAT, Swift-XRT, Swift-UVOT, ATOM and WISE are also analysed. Significant variability is observed only in the Fermi-LAT gamma-ray and Swift-XRT X-ray energy bands. Having a good multiwavelength coverage from radio to very high energy, we performed a broad-band modelling from two types of emission scenarios. The results from a one zone lepto-hadronic and a multizone leptonic models are compared and discussed. On the grounds of energetics, our analysis favours a leptonic multizone model. Models associated to the X-ray variability constraint support previous results, suggesting a BL Lac nature of PKS 0625-354 with, however, a large-scale jet structure typical of a radio galaxy.
Keywords: radiation mechanisms: non-thermal; galaxies: active; galaxies: individual: PKS 0625-354; galaxies: jets; gamma-rays: galaxies

H.E.S.S. discovery of VHE γ-rays from the quasar PKS 1510-089 - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Behera, B.; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2013)
The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E ≥ 0.1 TeV) emission. VHE γ-rays were detected with a statistical significance of 9.2 standard deviations in 15.8 h of H.E.S.S. data taken during March and April 2009. A VHE integral flux of I(0.15 TeV < E < 1.0TeV) = (1.0 ±0.2 ±0.2) ×10 cm s is measured. The best-fit power law to the VHE data has a photon index of γ = 5.4 ± 0.7 ± 0.3. The GeV and optical light curves show pronounced variability during the period of H.E.S.S. observations. However, there is insufficient evidence to claim statistically significant variability in the VHE data. Because of its relatively high redshift, the VHE flux from PKS 1510-089 should suffer considerable attenuation in the intergalactic space due to the extragalactic background light (EBL). Hence, the measured γ-ray spectrum is used to derive upper limits on the opacity due to EBL, which are found to be comparable with the previously derived limits from relatively-nearby BL Lac objects. Unlike typical VHE-detected blazars where the broadband spectrum is dominated by nonthermal radiation at all wavelengths, the quasar PKS 1510-089 has a bright thermal component in the optical to UV frequency band. Among all VHE detected blazars, PKS 1510-089 has the most luminous broad line region. The detection of VHE emission from this quasar indicates a low level of γ - γ absorption on the internal optical to UV photon field. © 2013 ESO.
Keywords: Gamma rays: galaxies; Infrared: diffuse background; Quasars: individual: PKS 1510; 089

HESS Follow-up Observations of Binary Black Hole Coalescence Events during the Second and Third Gravitational-wave Observing Runs of Advanced LIGO and Advanced Virgo - Abdalla, H.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Ashkar, H.; Backes, M.; Baghmanyan,; Martins, V. Barbosa; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlohr, K.; et al. (Astrophysical Journal, 2021)
We report on the observations of four well-localized binary black hole (BBH) mergers by the High Energy Stereoscopic System (H.E.S.S.) during the second and third observing runs of Advanced LIGO and Advanced Virgo, O2 and O3. H.E.S.S. can observe 20 deg(2) of the sky at a time and follows up gravitational-wave (GW) events by "tiling" localization regions to maximize the covered localization probability. During O2 and O3, H.E.S.S. observed large portions of the localization regions, between 35% and 75%, for four BBH mergers (GW170814, GW190512_180714, GW190728_064510, and S200224ca). For these four GW events, we find no significant signal from a pointlike source in any of the observations, and we set upper limits on the very high energy (>100 GeV) gamma-ray emission. The 1-10 TeV isotropic luminosity of these GW events is below 10(45) erg s(-1) at the times of the H.E.S.S. observations, around the level of the low-luminosity GRB 190829A. Assuming no changes are made to how follow-up observations are conducted, H.E.S.S. can expect to observe over 60 GW events per year in the fourth GW observing run, O4, of which eight would be observable with minimal latency.
CRIS-Team WoS Importer:2021-12-24

H.E.S.S. Follow-up Observations of GRB 221009A - Aharonian, F.; Benkhali, F. Ait; Aschersleben, J.; Ashkar, H.; Backes, M.; Baktash, A.; Martins, V. Barbosa; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Bi, B.; et al. (Astrophysical Journal Letters, 2023)
GRB 221009A is the brightest gamma-ray burst (GRB) ever detected. To probe the very-high-energy (VHE; >100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hr after the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection, after applying atmospheric corrections. The combined observations yield an integral energy flux upper limit of Φ UL 95 % = 9.7 × 10 − 12 erg cm − 2 s − 1 above E thr = 650 GeV. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the spectral energy distribution occurring above the X-ray band. Compared to the VHE-bright GRB 190829A, the upper limits for GRB 221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB 221009A, effectively ruling out an IC-dominated scenario.
CRIS-Team Scopus Importer:2023-04-14

H.E.S.S. II - Telescope structure, reflector and drive system - Deil, C.; van Eldik, Christopher; Förster, A.; Hermann, G.; Hofmann, W.; Panter, M. (4th International Meeting on High Energy Gamma-Ray Astronomy, 2009)
The currently operating phase I of the imaging atmospheric Cherenkov telescope array H.E.S.S. consists of four telescopes, each with a 107 m reflector, which are arranged on the corners of a square of 120 m side length. At the moment, the collaboration is building a much larger 600 m telescope in the center of the array. This will not only increase the sensitivity in the currently accessible energy regime, but will in addition lower the energy threshold of the system. The H.E.S.S. II telescope will have a parabolic reflector of 36 m focal length consisting of 850 individual mirrors, which can be automatically aligned, similar to the H.E.S.S. I telescopes. The drive system will have a repositioning speed of 100 deg/min in elevation and 200 deg/min in azimuth and achieve an online tracking accuracy of - 1 arcmin and an offline absolute pointing accuracy of - 10 arcsec. This proceeding contribution presents details on the technical implementation of the telescope mechanics, optics and drive system. © 2009 American Institute of Physics.
Keywords: Cherenkov telescope; H.E.S.S.

H.E.S.S. II-Telescope Structure, Reflector and Drive System - Deil, C.; van Eldik, Christopher; Förster, A.; Hermann, G.; Hofmann, W.; Panter, M. (American Institute of Physics Conference Series, 2008)
Keywords: Astronomical and space-research instrumentation; Particle acceleration; gamma-ray

HESS J0632+057: A NEW GAMMA-RAY BINARY? - Hinton, J. A.; Skilton, J. L.; Funk, Stefan; Brucker, Julia; Aharonian, F. A.; Dubus, Guillaume; Fiasson, A.; Gallant, Y.; Hofmann, W.; Marcowith, A.; Reimer, Olaf (Astrophysical Journal Letters, 2009)
The High Energy Stereoscopic System (HESS) survey of the Galactic plane has established the existence of a substantial number (similar to 40) of Galactic TeV gamma-ray sources, a large fraction of which remain unidentified. HESS J0632+057 is one of a small fraction of these objects, which is point-like in nature (< 2' rms), and is one of only two point-like sources that remain unidentified. Follow-up observations of this object with XMM-Newton have revealed an X-ray source coincident with the TeV source and with the massive star MWC 148, of the spectral type B0pe. This source exhibits a hard spectrum, consistent with an absorbed power law with Gamma = 1.26 +/- 0.04, and shows significant variability on hour timescales. We discuss this spatial coincidence and the implied spectral energy distribution of this object and argue that it is likely a new gamma-ray binary system with a close resemblance to the three known members of this class and, in particular, to LS I+61 303. Further, X-ray, radio, and optical observations of this system are needed to firmly establish HESS J0632+057 as a new member of this rare class of Galactic objects.
CRIS-Team WoS Importer:2020-01-15

HESS J1640-465-an exceptionally luminous TeV γ-ray supernova remnant - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Monthly Notices of the Royal Astronomical Society, 2014)
The results of follow-up observations of the TeV γ-ray source HESS J1640-465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well described by an exponential cut-offpower law with photon index γ = 2.11 ± 0.09 ± 0.10, and a cut-offenergy of E = 6.0 TeV. The TeV emission is significantly extended and overlaps with the northwestern part of the shell of the SNR G338.3-0.0. The new HESS results, a re-analysis of archival XMM-Newton data and multiwavelength observations suggest that a significant part of the γ-ray emission from HESS J1640-465 originates in the supernova remnant shell. In a hadronic scenario, as suggested by the smooth connection of the GeV and TeV spectra, the product of total proton energy and mean target density could be as high as W 4 × 10(d/10kpc) erg cm. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Keywords: G338.3-0.0-ISM; Individual objects; Non-thermal-ISM; Radiation mechanisms; Supernova remnants

HESS J1741-302: a hidden accelerator in the Galactic plane - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Angüner, E. O.; Arakawa, M.; Armand, C.; Arrieta, M.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; et al. (Astronomy & Astrophysics, 2018)
The H.E.S.S. Collaboration has discovered a new very high energy (VHE, E > 0.1 TeV) gamma-ray source, HESS J1741-302, located in the Galactic plane. Despite several attempts to constrain its nature, no plausible counterpart has been found so far at X-ray and MeV/GeV gamma-ray energies, and the source remains unidentified. An analysis of 145-h of observations of HESS J1741-302 at VHEs has revealed a steady and relatively weak TeV source (similar to 1% of the Crab Nebula flux), with a spectral index of Gamma = 2.3 +/- 0.2(stat) +/- 0.2(sys), extending to energies up to 10 TeV without any clear signature of a cut-off. In a hadronic scenario, such a spectrum implies an object with particle acceleration up to energies of several hundred TeV. Contrary to most H.E.S.S. unidentified sources, the angular size of HESS J1741-302 is compatible with the H.E.S.S. point spread function at VHEs, with an extension constrained to be below 0.068 degrees at a 99% confidence level. The gamma-ray emission detected by H.E.S.S. can be explained both within a hadronic scenario, due to collisions of protons with energies of hundreds of TeV with dense molecular clouds, and in a leptonic scenario, as a relic pulsar wind nebula, possibly powered by the middle-aged (20 kyr) pulsar PSR B1737-30. A binary scenario, related to the compact radio source 1LC 358.266+0.038 found to be spatially coincident with the best fit position of HESS J1741-302, is also envisaged.
Keywords: gamma rays: ISM; gamma rays: general; cosmic rays; ISM: clouds

HESS J1809-193: A halo of escaped electrons around a pulsar wind nebula? - Aharonian, F.; Ait Benkhali, F.; Aschersleben, J.; Ashkar, H.; Backes, M.; Barbosa Martins, V.; Batzofin, R.; Becherini, Y.; Berge, D.; Boettcher, M.; Boisson, C.; Bolmont, J.; et al. (Astronomy & Astrophysics, 2023)
Context. HESS J1809-193 is an unassociated very-high-energy gamma-ray source located on the Galactic plane. While it has been connected to the nebula of the energetic pulsar PSR J1809-1917, supernova remnants and molecular clouds present in the vicinity also constitute possible associations. Recently, the detection of gamma-ray emission up to energies of similar to 100 TeV with the HAWC observatory has led to renewed interest in HESS J1809-193.Aims. We aim to understand the origin of the gamma-ray emission of HESS J1809-193.Methods. We analysed 93.2 h of data taken on HESS J1809-193 above 0.27 TeV with the High Energy Stereoscopic System (H.E.S.S.), using a multi-component, three-dimensional likelihood analysis. In addition, we provide a new analysis of 12.5 yr of Fermi-LAT data above 1 GeV within the region of HESS J1809-193. The obtained results are interpreted in a time-dependent modelling framework.Results. For the first time, we were able to resolve the emission detected with H.E.S.S. into two components: an extended component (modelled as an elongated Gaussian with a 1-sigma semi-major and semi-minor axis of similar to 0.62 degrees and similar to 0.35 degrees, respectively) that exhibits a spectral cutoff at similar to 13 TeV, and a compact component (modelled as a symmetric Gaussian with a 1-sigma radius of similar to 0.1 degrees) that is located close to PSR J1809-1917 and shows no clear spectral cutoff. The Fermi-LAT analysis also revealed extended gamma-ray emission, on scales similar to that of the extended H.E.S.S. component.Conclusions. Our modelling indicates that based on its spectrum and spatial extent, the extended H.E.S.S. component is likely caused by inverse Compton emission from old electrons that form a halo around the pulsar wind nebula. The compact component could be connected to either the pulsar wind nebula or the supernova remnant and molecular clouds. Due to its comparatively steep spectrum, modelling the Fermi-LAT emission together with the H.E.S.S. components is not straightforward.
CRIS-Team WoS Importer:2023-05-05

HESS J1818-154, a new composite supernova remnant discovered in TeV gamma rays and X-rays - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2014)
Composite supernova remnants (SNRs) constitute a small subclass of the remnants of massive stellar explosions where non-thermal radiation is observed from both the expanding shell-like shock front and from a pulsar wind nebula (PWN) located inside of the SNR. These systems represent a unique evolutionary phase of SNRs where observations in the radio, X-ray, and γ-ray regimes allow the study of the co-evolution of both these energetic phenomena. In this article, we report results from observations of the shell-type SNR G 15.4+0.1 performed with the High Energy Stereoscopic System (H.E.S.S.) and XMM-Newton. A compact TeV γ-ray source, HESS J1818-154, located in the center and contained within the shell of G 15.4+0.1 is detected by H.E.S.S. and featurs a spectrum best represented by a power-law model with a spectral index of-2.3 ± 0.3 ± 0.2 and an integral flux of F(> 0.42 TeV) = (0.9 ± 0.3 ± 0.2) × 10 cm s. Furthermore, a recent observation with XMM-Newton reveals extended X-ray emission strongly peaked in the center of G 15.4+0.1. The X-ray source shows indications of an energy-dependent morphology featuring a compact core at energies above 4 keV and more extended emission that fills the entire region within the SNR at lower energies. Together, the X-ray and VHE γ-ray emission provide strong evidence of a PWN located inside the shell of G 15.4+0.1 and this SNR can therefore be classified as a composite based on these observations. The radio, X-ray, and γ-ray emission from the PWN is compatible with a one-zone leptonic model that requires a low average magnetic field inside the emission region. An unambiguous counterpart to the putative pulsar, which is thought to power the PWN, has been detected neither in radio nor in X-ray observations of G 15.4+0.1. © 2014 ESO.
Keywords: Gamma rays: general; Methods: observational; Supernovae: individual: HESS J1818-154; X-rays: general; X-rays: individuals: G15.4+0.1

HESS J1825-137: A pulsar wind nebula associated with PSR B1823-13? - Funk, Stefan; et al. (Proceedings of the 29th International Cosmic Ray Conference, Vol 4: OG 2.1, 2.2 & 2.3, 2005)
CRIS-Team WoS Importer:2020-01-15

HESS J1943+213: A candidate extreme BL Lacertae object - van Eldik, Christopher; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Becker, J.; et al. (Astronomy & Astrophysics, 2011)
Context. The H.E.S.S. Cherenkov telescope array has been surveying the Galactic plane for new VHE (>100 GeV) gamma-ray sources. Aims. We report on a newly detected point-like source, HESS J1943+213. This source coincides with an unidentified hard X-ray source IGR J19443+2117, which was proposed to have radio and infrared counterparts. Methods. We combine new H.E.S.S., Fermi/LAT and Nançay Radio Telescope observations with pre-existing non-simultaneous multi-wavelength observations of IGR J19443+2117 and discuss the likely source associations as well as the interpretation as an active galactic nucleus, a gamma-ray binary or a pulsar wind nebula. Results. HESS J1943+213 is detected at the significance level of 7.9σ (post-trials) at RA(J2000)= 19 4355 ± 1 ± 1 , Dec(J2000)= +21° 18'8" ± 17" ± 20". The source has a soft spectrum with photon index Γ = 3.1 ± 0.3 ± 0.2 and a flux above 470 GeV of (1.3 ± 0.2 ± 0.3) × 10 cm s . There is no Fermi/LAT counterpart down to a flux limit of 6 × 10 cm s in the 0.1-100 GeV energy range (95% confidence upper limit calculated for an assumed power-law model with a photon index Γ = 2.0). The data from radio to VHE gamma-rays do not show any significant variability. Conclusions. The lack of a massive stellar counterpart disfavors the binary hypothesis, while the soft VHE spectrum would be very unusual in case of a pulsar wind nebula. In addition, the distance estimates for Galactic counterparts places them outside of the Milky Way. All available observations favor an interpretation as an extreme, high-frequency peaked BL Lac object with a redshift z > 0.14. This would be the first time a blazar is detected serendipitously from ground-based VHE observations, and the first VHE AGN detected in the Galactic Plane. © 2011 ESO.
Keywords: BL Lacertae objects: individual: IGR J19443+2117; galaxies: active; gamma rays: general

H.E.S.S. Limits on Linelike Dark Matter Signatures in the 100 GeV to 2 TeV Energy Range Close to the Galactic Center - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Andersson, T.; Anguener, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; et al. (Physical Review Letters, 2016)
A search for dark matter linelike signals iss performed in the vicinity of the Galactic Center by the H.E.S.S. experiment on observational data taken in 2014. An unbinned likelihood analysis iss developed to improve the sensitivity to linelike signals. The upgraded analysis along with newer data extend the energy coverage of the previous measurement down to 100 GeV. The 18 h of data collected with the H.E.S.S. array allow one to rule out at 95% C.L. the presence of a 130 GeV line (at l=-1.5°, b=0° and for a dark matter profile centered at this location) previously reported in Fermi-LAT data. This new analysis overlaps significantly in energy with previous Fermi-LAT and H.E.S.S. results. No significant excess associated with dark matter annihilations was found in the energy range of 100 GeV to 2 TeV and upper limits on the gamma-ray flux and the velocity weighted annihilation cross section are derived adopting an Einasto dark matter halo profile. Expected limits for present and future large statistics H.E.S.S. observations are also given.

Hess observarions of the prompt and afterglow phases of GRB 060602B - Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, W.; Bernloehr, K.; Boisson, C.; Borrel, V.; Braun, Isabel V; Brion, E.; et al. (Astrophysical Journal, 2009)
We report on the first completely simultaneous observation of a gamma-ray burst (GRB) using an array of Imaging Atmospheric Cherenkov Telescopes, which is sensitive to photons in the very high energy (VHE) γ-ray range (≳ 100 GeV). On 2006 June 2, the Swift Burst Alert Telescope (BAT) registered an unusually soft γ-ray burst (GRB 060602B). The burst position was under observation using the High Energy Stereoscopic System (HESS) at the time the burst occurred. Data were taken before, during, and after the burst. A total of 5 hr of observations were obtained during the night of 2006 June 2-3, and five additional hours were obtained over the next three nights. No VHE γ-ray signal was found during the period covered by the HESS observations. The 99% confidence level flux upper limit (> 1 TeV) for the prompt phase (9 s) of GRB 060602B is 2.9 × 10 erg cm s. Due to the very soft BAT spectrum of the burst compared with other Swift GRBs and its proximity to the Galactic center, the burst is likely associated with a Galactic X-ray burster, although the possibility of it being a cosmological GRB cannot be ruled out. We discuss the implications of our flux limits in the context of these two bursting scenarios. © 2009. The American Astronomical Society. All rights reserved.
Keywords: Bursts-gamma rays; Gamma rays; Observations

HESS observations and VLT spectroscopy of PG 1553+113 - Aharonian, F.; Akhperjanian, A. G.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Behera, B.; Beilicke, M.; Benbow, W.; Bernloehr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, Isabel V; et al. (Astronomy & Astrophysics, 2008)
Keywords: galaxies: active; galaxies: BL Lacertae objects: individual: PG 1553+113; gamma rays: observations

HESS observations of PKS 2155-304 - Funk, Stefan; et al. (Astronomy & Astrophysics, 2005)
The high-frequency peaked BL Lac PKS 2155-304 at redshift z=0.117 has been detected with high significance (similar to45sigma) at energies greater than 160 GeV, using the H.E.S.S. stereoscopic array of imaging air-Cherenkov telescopes in Namibia. A strong signal is found in each of the data sets corresponding to the dark periods of July and October, 2002, and June-September, 2003. The observed flux of VHE gamma rays shows variability on time scales of months, days, and hours. The monthly-averaged integral flux above 300 GeV varies between 10% and 60% of the flux observed from the Crab Nebula. Energy spectra are measured for these individual periods of data taking and are characterized by a steep power law with a time-averaged photon index of Gamma=3.32+/-0.06. An improved chi(2) per degree of freedom is found when either a power law with an exponential cutoff energy or a broken power law are fit to the time-averaged energy spectrum. However, the significance of the improvement is marginal (similar to2sigma). The suggested presence of features in the energy spectrum may be intrinsic to the emission from the blazar, or an indication of absorption of TeV gamma rays by the extragalactic infrared background light.
CRIS-Team WoS Importer:2020-01-15

HESS observations of RX J1713.7-3946 with improved angular and spectral resolution: Evidence for gamma-ray emission extending beyond the X-ray emitting shell - Abdalla, H.; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Andersson, T.; Anguener, E. O.; Arrieta, M.; Aubert, P.; Backes, Michael; Balzer, A.; Barnard, Monica; et al. (Astronomy & Astrophysics, 2018)
Supernova remnants exhibit shock fronts (shells) that can accelerate charged particles up to very high energies. In the past decade, measurements of a handful of shell-type supernova remnants in very high-energy gamma rays have provided unique insights into the acceleration process. Among those objects, RX J1713.7-3946 (also known as G347.3-0.5) has the largest surface brightness, allowing us in the past to perform the most comprehensive study of morphology and spatially resolved spectra of any such very high-energy gamma-ray source. Here we present extensive new H.E.S.S. measurements of RX J1713.7-3946, almost doubling the observation time compared to our previous publication. Combined with new improved analysis tools, the previous sensitivity is more than doubled. The H.E.S.S. angular resolution of 0.048 degrees (0.036 degrees above 2 TeV) is unprecedented in gamma-ray astronomy and probes physical scales of 0.8 (0.6) parsec at the remnant's location. The new H. E. S. S. image of RX J1713.7-3946 allows us to reveal clear morphological di ff erences between X-rays and gamma rays. In particular, for the outer edge of the brightest shell region, we find the first ever indication for particles in the process of leaving the acceleration shock region. By studying the broadband energy spectrum, we furthermore extract properties of the parent particle populations, providing new input to the discussion of the leptonic or hadronic nature of the gamma-ray emission mechanism.
CRIS-Team WoS Importer:2020-01-15
Keywords: ISM: Supernova remnants; cosmic rays; gamma rays: General; Acceleration of particles; astroparticle physic

H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; Birsin, E.; et al. (Astronomy & Astrophysics, 2013)
Aims. We present very high energy (VHE; E > 100 GeV) data from the γ-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov Telescopes. We aim to search for a possible TeV counterpart of the GeV flare detected by the Fermi LAT. In addition, we aim to study the current periastron passage in the context of previous observations taken at similar orbital phases, testing the repetitive behaviour of the source. Methods. Observations at VHEs were conducted with H.E.S.S. from 9th to 16th of January 2011. The total dataset amounts to 6 h of observing time. The data taken around the 2004 periastron passage were also re-analysed with the current analysis techniques in order to extend the energy spectrum above 3 TeV to fully compare observation results from 2004 and 2011. Results. The source is detected in the 2011 data at a significance level of 11.5σ revealing an averaged integral flux above 1 TeV of (1.01 ± 0.18 ± 0.20) × 10 cm s. The differential energy spectrum follows a power-law shape with a spectral index Γ = 2.92 ± 0.30 ± 0.20 and a flux normalisation at 1 TeV of N = (1.95 ± 0.32 ± 0.39) × 10 TeV cm s. The measured light curve does not show any evidence for variability of the source on the daily scale. The re-analysis of the 2004 data yields results compatible with the published ones. The differential energy spectrum measured up to 10 TeV is consistent with a power law with a spectral index Γ = 2.81 ± 0.10 ± 0.20 and a flux normalisation at 1 TeV of N = (1.29 ± 0.08 ± 0.26) × 10 TeV cm s. Conclusions. The measured integral flux and the spectral shape of the 2011 data are compatible with the results obtained around previous periastron passages. The absence of variability in the H.E.S.S. data indicates that the GeV flare observed by Fermi LAT in the time period covered also by H.E.S.S. observations originates in a different physical scenario than the TeV emission. Moreover, the comparison of the new results to the results from the 2004 observations made at a similar orbital phase provides a stronger evidence of the repetitive behaviour of the source. © ESO, 2013.
Keywords: Gamma rays: general; Pulsars: individual: PSR B1259-63; Stars: individual: LS 2883; X-rays: binaries

HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; Becherini, Y.; Becker, J.; Bernloehr, K.; Birsin, E.; Biteau, J.; et al. (Monthly Notices of the Royal Astronomical Society, 2012)
The massive binary system Eta Carinae and the surrounding Hii complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E≥ 100GeV) γ-ray emission could be expected. This paper presents data collected during VHE γ-ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant γ-ray emission from Eta Carinae has been found and an upper limit on the γ-ray flux of (99per cent confidence level) is derived above the energy threshold of 470GeV. Together with the detection of high energy (HE; 0.1 ≤E≤ 100GeV) γ-ray emission by the Fermi Large Area Telescope up to 100GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the γ-ray spectrum between the HE and VHE γ-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe γ-γ absorption losses in the wind collision region. Furthermore, the search for extended γ-ray emission from the Carina nebula resulted in an upper limit on the γ-ray flux of (99per cent confidence level). The derived upper limit of ∼23 on the cosmic ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W28. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
Keywords: Acceleration of particles; ISM: individual objects: Carina nebula; ISM: individual objects: Eta Carina; Open clusters and associations: general; Radiation mechanisms: non-thermal; X-rays: binaries

H.E.S.S. observations of the Crab during its March 2013 GeV gamma-ray flare - Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Anguener, E.; Anton, Gisela; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Tjus, J. Becker; Bernloehr, K.; et al. (Astronomy & Astrophysics, 2014)
Context. On March 4, 2013 the Fermi-LAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us hints about the emission processes during the flare episode and the physics of pulsar wind nebulae in general. Aims. We search for variability in the emission of the Crab nebula at very-high energies (VHE; E > 100 GeV), using contemporaneous data taken with the H.E.S.S. array of Cherenkov telescopes. Methods. Observational data taken with the H.E.S.S. instrument on five consecutive days during the flare were analysed for the flux and spectral shape of the emission from the Crab nebula. Night-wise light curves are presented with energy thresholds of 1 TeV and 5 TeV. Results. The observations conducted with H.E.S.S. on March 6 to March 10, 2013 show no significant changes in the flux. They limit the variation in the integral flux above 1 TeV to less than 63% and the integral flux above 5 TeV to less than 78% at a 95% confidence level. © 2014 ESO.
Keywords: Gamma rays: ISM; ISM: individual objects: Crab nebula; Radiation mechanisms: non-thermal; Relativistic processes

HESS observations of the flaring gravitationally lensed galaxy PKS 1830-211 - Abdalla, H.; Aharonian, F.; Benkhali, F. Ait; Anguner, E. O.; Arakawa, M.; Arcaro, C.; Armand, C.; Arrieta, M.; Backes, M.; Barnard, M.; Becherini, Y.; Tjus, J. Becker; et al. (Monthly Notices of the Royal Astronomical Society, 2019)
PKS 1830-211 is a known macrolensed quasar located at a redshift of z = 2.5. Its highenergy gamma-ray emission has been detected with the Fermi-Large Area Telescope (LAT) instrument and evidence for lensing was obtained by several authors from its high-energy data. Observations of PKS 1830-211 were taken with the High Energy Stereoscopic System (H.E.S.S.) array of Imaging Atmospheric Cherenkov Telescopes in 2014 August, following a flare alert by the Fermi-LAT Collaboration. The H.E.S.S observations were aimed at detecting a gamma-ray flare delayed by 20-27 d from the alert flare, as expected from observations at other wavelengths. More than 12 h of good-quality data were taken with an analysis threshold of similar to 67 GeV. The significance of a potential signal is computed as a function of the date and the average significance over the whole period. Data are compared to simultaneous observations by Fermi-LAT. No photon excess or significant signal is detected. An upper limit on PKS 1830-211 flux above 67 GeV is computed and compared to the extrapolation of the Fermi-LAT flare spectrum.
CRIS-Team WoS Importer:2019-07-26
Keywords: gamma-rays: galaxies; gravitational lensing: strong; diffuse radiation

HESS observations of the galactic center region and their possible dark matter interpretation - van Eldik, Christopher; et al. (Physical Review Letters, 2006)
The detection of γ rays from the source HESS J1745-290 in the Galactic Center (GC) region with the High Energy Spectroscopic System (HESS) array of Cherenkov telescopes in 2004 is presented. After subtraction of the diffuse γ-ray emission from the GC ridge, the source is compatible with a point source with spatial extent less than 1.2′(stat) (95% C.L.). The measured energy spectrum above 160 GeV is compatible with a power law with photon index of 2.25±0.04(stat)±0.10(syst) and no significant flux variation is detected. It is finally found that the bulk of the very high energy emission must have non-dark-matter origin. © 2006 The American Physical Society.

H.E.S.S. observations of the globular clusters NGC 6388 and M15 and search for a dark matter signal - Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, Gisela; Balzer, Arnim; Barnacka, A.; De Almeida, U. Barres; Bazer-Bachi, A. R.; Becherini, Y.; Becker, J.; Behera, B.; et al. (Astrophysical Journal, 2011)
Observations of the globular clusters (GCs) NGC 6388 and M15 were carried out by the High Energy Stereoscopic System array of Cherenkov telescopes for a live time of 27.2 and 15.2 hr, respectively. No gamma-ray signal is found at the nominal target position of NGC 6388 and M15. In the primordial formation scenario, GCs are formed in a dark matter (DM) halo and DM could still be present in the baryon-dominated environment of GCs. This opens the possibility of observing a DM self-annihilation signal. The DM content of the GCs NGC 6388 and M15 is modeled taking into account the astrophysical processes that can be expected to influence the DM distribution during the evolution of the GC: the adiabatic contraction of DM by baryons, the adiabatic growth of a black hole in the DM halo, and the kinetic heating of DM by stars. Ninety-five percent confidence level exclusion limits on the DM particle velocity-weighted annihilation cross section are derived for these DM halos. In the TeV range, the limits on the velocity-weighted annihilation cross section are derived at the 10 cm s level and a few 10 cm s for NGC 6388 and M15, respectively. © 2011. The American Astronomical Society. All rights reserved..
Keywords: black hole physics; dark matter; gamma rays: general; globular clusters: individual (NGC 6388; M15)

(untitled) - van Eldik, Christopher; et al.