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@article{faucris.261853001,
abstract = {Supernovae Ia are bright explosive events that can be used to estimate cosmological distances, allowing us to study the expansion of the Universe. They are understood to result from a thermonuclear detonation in a white dwarf that formed from the exhausted core of a star more massive than the Sun. However, the possible progenitor channels leading to an explosion are a long-standing debate, limiting the precision and accuracy of supernovae Ia as distance indicators. Here we present HD 265435, a binary system with an orbital period of less than a hundred minutes that consists of a white dwarf and a hot subdwarf, which is a stripped core-helium-burning star. The total mass of the system is 1.65 +/- 0.25 solar masses, exceeding the Chandrasekhar limit (the maximum mass of a stable white dwarf). The system will merge owing to gravitational wave emission in 70 million years, likely triggering a supernova Ia event. We use this detection to place constraints on the contribution of hot subdwarf-white dwarf binaries to supernova Ia progenitors.},
author = {Pelisoli, Ingrid and Neunteufel, P. and Geier, S. and Kupfer, T. and Heber, Ulrich and Irrgang, Andreas and Schneider, David and Bastian, A. and Van Roestel, J. and Schaffenroth, and Barlow, B. N.},
doi = {10.1038/s41550-021-01413-0},
faupublication = {yes},
journal = {Nature Astronomy},
note = {CRIS-Team WoS Importer:2021-07-23},
peerreviewed = {Yes},
title = {{A} hot subdwarf-white dwarf super-{Chandrasekhar} candidate supernova {Ia} progenitor},
year = {2021}
}
@article{faucris.107330124,
abstract = {The KM3NeT research infrastructure, currently under construction in the Mediterranean Sea, will host neutrino telescopes for the identification of neutrino sources in the Universe and for studies of the neutrino mass hierarchy. These telescopes will house hundreds of thousands of photomultiplier tubes that will have to be operated in a stable and reliable fashion. In this context, the stability of the dark counts has been investigated for photomultiplier tubes with negative high voltage on the photocathode and held in insulating support structures made of 3D printed nylon material. Small gaps between the rigid support structure and the photomultiplier tubes in the presence of electric fields can lead to discharges that produce dark count rates that are highly variable. A solution was found by applying the same insulating varnish as used for the high voltage bases directly to the outside of the photomultiplier tubes. This transparent conformal coating provides a convenient and inexpensive method of insulation.},
author = {Adrián-Martínez, S. and Ageron, M. and Aiello, S. and Albert, A. and Ameli, F. and Anassontzis, E. G. and Andre, M. and Androulakis, G. and Anghinolfi, M. and Anton, Gisela and Ardid, M. and Avgitas, T. and Barbarino, G. and Barbarito, E. and Baret, B. and Barrios-Martí, J. and Belias, A. and Berbee, E. and Van Den Berg, A. and Bertin, V. and Beurthey, S. and Van Beveren, V. and Beverini, N. and Biagi, S. and Biagioni, A. and Billault, M. and Bondì, M. and Bormuth, R. and Bouhadef, B. and Bourlis, G. and Bourret, S. and Boutonnet, C. and Bouwhuis, M. and Bozza, C. and Bruijn, R. and Brunner, J. and Buis, E. and Buompane, R. and Busto, J. and Cacopardo, G. and Caillat, L. and Calamai, M. and Calvo, D. and Capone, A. and Caramete, L. and Cecchini, S. and Celli, S. and Champion, C. and Cherubini, S. and Chiarella, V. and Chiarelli, L. and Chiarusi, T. and Circella, M. and Classen, Lew and Cobas, D. and Cocimano, R. and Coelho, J. A.B. and Coleiro, A. and Colonges, S. and Coniglione, R. and Cordelli, M. and Cosquer, A. and Coyle, P. and Creusot, A. and Cuttone, G. and D'Amato, C. and D'Amico, A. and D'Onofrio, A. and De Bonis, G. and De Sio, C. and Di Capua, F. and Di Palma, I. and Distefano, C. and Donzaud, C. and Dornic, D. and Dorosti-Hasankiadeh, Q. and Drakopoulou, E. and Drouhin, D. and Durocher, M. and Eberl, Thomas and Eichie, Sebastian and Van Eijk, D. and El Bojaddaini, I. and Elsaesser, D. and Enzenhöfer, A. and Favaro, M. and Fermani, P. and Ferrara, G. and Frascadore, G. and Furini, M. and Fusco, L. A. and Gál, Tamás and Galatà, S. and Garufi, F. and Gay, P. and Gebyehu, M. and Giacomini, F. and Gialanella, L. and Giordano, V. and Gizani, N. and Gracia, R. and Graf, Kay and Grégoire, T. and Grella, G. and Grmek, A. and Guerzoni, M. and Habel, R. and Hallmann, Steffen and Van Haren, H. and Harissopulos, S. and Heid, Thomas and Heijboer, A. and Heine, E. and Henry, S. and Hernández-Rey, J. J. and Hevinga, M. and Hofestädt, Jannik and Hugon, C. M.F. and Illuminati, G. and James, Clancy and Jansweijer, P. and Jongen, M. and De Jong, M. and Kadler, M. and Kalekin, O. and Kappes, Alexander and Katz, Uli and Keller, P. and Kieft, G. and Kießling, Dominik and Koffeman, E. N. and Kooijman, P. and Kouchner, A. and Kreter, M. and Kulikovskiy, V. and Lahmann, Robert and Lamare, P. and Leisos, A. and Leonora, E. and Clark, M. Lindsey and Liolios, A. and Alvarez, C. D.Llorens and Lo Presti, D. and Löhner, H. and Lonardo, A. and Lotze, M. and Loucatos, S. and Maccioni, E. and Mannheim, K. and Manzali, M. and Margiotta, A. and Margotti, A. and Marinelli, A. and Mariš, O. and Markou, C. and Martínez-Mora, J. A. and Martini, A. and Marzaioli, F. and Mele, R. and Melis, K. W. and Michael, T. and Migliozzi, P. and Migneco, E. and Mijakowski, P. and Miraglia, A. and Mollo, C. M. and Mongelli, M. and Morganti, M. and Moussa, A. and Musico, P. and Musumeci, M. and Nicolau, C. A. and Olcina, I. and Olivetto, C. and Orlando, A. and Orzelli, A. and Pancaldi, G. and Paolucci, A. and Papaikonomou, A. and Papaleo, R. and Pǎvǎlaš, G. E. and Peek, H. and Pellegrini, G. and Pellegrino, C. and Perrina, C. and Pfutzner, M. and Piattelli, P. and Pikounis, K. and Poma, G. E. and Popa, V. and Pradier, T. and Pratolongo, F. and Pühlhofer, G. and Pulvirenti, S. and Quinn, L. and Racca, C. and Raffaelli, F. and Randazzo, N. and Real, D. and Resvanis, L. and Reubelt, Jonas and Riccobene, G. and Rossi, C. and Rovelli, A. and Saldaña, M. and Salvadori, I. and Samtleben, D. F.E. and Sánchez García, A. and Sánchez Losa, A. and Sanguineti, M. and Santangelo, A. and Santonocito, D. and Sapienza, P. and Schimmel, F. and Schmelling, J. and Schnabel, Jutta and Sciacca, V. and Sedita, M. and Seitz, Thomas and Sgura, I. and Simeone, F. and Sipala, V. and Spisso, B. and Spurio, M. and Stavropoulos, G. and Steijger, J. and Stellacci, S. M. and Stransky, Dominik and Taiuti, M. and Tayalati, Y. and Terrasi, F. and Tézier, D. and Theraube, S. and Timmer, P. and Tönnis, C. and Trasatti, L. and Travaglini, R. and Trovato, A. and Tsirigotis, A. and Tzamarias, S. and Tzamariudaki, E. and Vallage, B. and Van Elewyck, V. and Vermeulen, J. and Versari, F. and Vicini, P. and Viola, S. and Vivolo, D. and Volkert, Marco and Wiggers, L. and Wilms, Jörn and De Wolf, E. and Zachariadou, K. and Zani, S. and Zornoza, J. D. and Zúñiga, J.},
doi = {10.1088/1748-0221/11/12/P12014},
faupublication = {yes},
journal = {Journal of Instrumentation},
keywords = {Instrument optimization; Large detector systems for particle and astroparticle physics; Neutrino detectors; Photon detectors for UV, visible and IR photons (gas) (gas-photocathodes, solid-photocathodes)},
peerreviewed = {Yes},
title = {{A} method to stabilise the performance of negatively fed {KM3NeT} photomultipliers},
volume = {11},
year = {2016}
}
@article{faucris.246888411,
abstract = {Aims. We selected the bluest object, WISE J0725-2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to unravel the nature of this relatively bright (V similar to 12, J similar to 11) HPM star (mu = 267 mas/yr).Methods. We obtained low-and medium-resolution spectra with the European Southern Observatory (ESO) New Technology Telescope (NTT)/EFOSC2 and Very Large Telescope (VLT)/X-Shooter instruments, investigated the radial velocity and performed a quantitative spectral analysis that allowed us to determine physical parameters. The fit of the spectral energy distribution based on the available photometry to low-metallicity model spectra and the similarity of our target to a metal-poor benchmark star (HD 84937) allowed us to estimate the distance and space velocity.Results. As in the case of HD 84937, we classified WISE J0725-2351 as sdF5: or a metal-poor turnoff star with [Fe/H] = -2.0 +/- 0.2, T-eff = 6250 +/- 100 K, log g = 4.0 +/- 0.2, and a possible age of about 12 Gyr. At an estimated distance of more than 400 pc, its proper motion translates to a tangential velocity of more than 500 km s(-1). Together with its constant (on timescales of hours, days, and months) and large radial velocity (about +240 km s(-1)), the resulting Galactic restframe velocity is about 460 km s(-1), implying a bound retrograde orbit for this extreme halo object that currently crosses the Galactic plane at high speed.},
author = {Scholz, R. -D. and Heber, Ulrich and Heuser, Christian and Ziegerer, Eva and Geier, Stephan and Niederhofer, F},
doi = {10.1051/0004-6361/201425471},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {proper motions;stars: distances;stars: kinematics and dynamics;stars: Population II;subdwarfs;white dwarfs},
peerreviewed = {Yes},
title = {{An} ancient {F}-type subdwarf from the halo crossing the {Galactic} plane},
volume = {574},
year = {2015}
}
@article{faucris.246874314,
abstract = {We present the discovery of the second binary with a Roche lobe-filling hot subdwarf transferring mass to a white dwarf (WD) companion. This 56 minute binary was discovered using data from the Zwicky Transient Facility. Spectroscopic observations reveal an He-sdOB star with an effective temperature ofT(eff) = 33,700 1000 K and a surface gravity of log(g) = 5.54 0.11. The GTC+HiPERCAM light curve is dominated by the ellipsoidal deformation of the He-sdOB star and shows an eclipse of the He-sdOB by an accretion disk as well as a weak eclipse of the WD. We infer a He-sdOB mass ofM(sdOB) = 0.41 0.04Mand a WD mass ofM(WD) = 0.68 0.05M. The weak eclipses imply a WD blackbody temperature of 63,000 10,000 K and a radiusR(WD) = 0.0148 0.0020Ras expected for a WD of such high temperature. The He-sdOB star is likely undergoing hydrogen shell burning and will continue transferring mass for 1 Myr at a rate of 10(-9)Myr(-1), which is consistent with the high WD temperature. The hot subdwarf will then turn into a WD and the system will merge in 30 Myr. We suggest that Galactic reddening could bias discoveries toward preferentially finding Roche lobe-filling systems during the short-lived shell-burning phase. Studies using reddening-corrected samples should reveal a large population of helium core-burning hot subdwarfs withT(eff) 25,000 K in binaries of 60-90 minutes with WDs. Though not yet in contact, these binaries would eventually come into contact through gravitational-wave emission and explode as a subluminous thermonuclear supernova or evolve into a massive single WD.},
author = {Kupfer, Thomas and Bauer, Evan and Burdge, Kevin and van Roestel, Jan and Bellm, Eric and Fuller, Jim and Hermes, JJ and Marsh, Thomas R. and Bildsten, Lars and Kulkarni, Shrinivas R and Phinney, E S and Prince, Thomas A and Szkody, Paula and Yao, Yuhan and Heber, Ulrich and Schneider, David and Dhillon, V. S. and Murawski, Gabriel and Drake, Andrew J and Duev, Dmitry A and Feeney, Michael and Graham, Matthew J and Laher, Russ R and Littlefair, S. P. and Mahabal, A A and Masci, Frank J and Porter, Michael and Reiley, Dan and Rodriguez, Hector and Rusholme, Ben and Shupe, David L and Soumagnac, Maayane T and Irrgang, Andreas},
doi = {10.3847/2041-8213/aba3c2},
faupublication = {yes},
journal = {Astrophysical Journal Letters},
keywords = {B subdwarf stars;Stellar evolution;White dwarf stars;Compact binary stars;Stellar accretion},
peerreviewed = {Yes},
title = {{A} {New} {Class} of {Roche} {Lobe}-filling {Hot} {Subdwarf} {Binaries}},
volume = {898},
year = {2020}
}
@article{faucris.261050899,
abstract = {In the past, SDSS J160429.12+100002.2 wass spectroscopically classified as a blue horizontal branch (BHB) star. Assuming a luminosity that is characteristic of BHB stars, the object's radial velocity and proper motions from Gaia Early Data Release 3 would imply that its Galactic rest-frame velocity exceeds its local escape velocity. Consequently, the object would be considered a hypervelocity star, which would prove particularly interesting because its Galactic trajectory points in our direction. However, based on the spectroscopic analysis of follow-up observations, we show that the object is actually a short-period (P ≈ 3.4 h) single-lined spectroscopic binary system with a visible B-type star (effective temperature Teff = 15 840 ± 160 K and surface gravity log(g) = 4.86 ± 0.04) that is less luminous than typical BHB stars. Accordingly, the distance of the system is lower than originally thought, which renders its Galactic orbit bound to the Galaxy. Nevertheless, it is still an extreme halo object on a highly retrograde orbit. The abundances of He, C, N, O, Ne, Mg, Al, Si, S, and Ca are subsolar by factors from 3 to more than 100, while Fe is enriched by a factor of about 6. This peculiar chemical composition pattern is most likely caused by atomic diffusion processes. Combining constraints from astrometry, orbital motion, photometry, and spectroscopy, we conclude that the visible component is an unevolved proto-helium white dwarf with a thin hydrogen envelope that was stripped by a substellar companion through common-envelope ejection. Its unique configuration renders the binary system an interesting test bed for stellar binary evolution in general and common-envelope evolution in particular. },
author = {Irrgang, Andreas and Geier, S. and Heber, Ulrich and Kupfer, T. and El-Badry, K. and Bloemen, S.},
doi = {10.1051/0004-6361/202038757},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Binaries: Close; Binaries: Spectroscopic; Brown dwarfs; Stars: Chemically peculiar; Stars: Individual: SDSS J160429.12+100002.2; White dwarfs},
note = {CRIS-Team Scopus Importer:2021-07-02},
peerreviewed = {Yes},
title = {{A} proto-helium white dwarf stripped by a substellar companion via common-envelope ejection: {Uncovering} the true nature of a candidate hypervelocity {B}-type star},
volume = {650},
year = {2021}
}
@article{faucris.246881441,
abstract = {Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-type subdwarfs (sdB), the origin of the helium dominated subclass of O-type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra.Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using TLUSTY200/SYNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models.Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000K and 47 000K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31 degrees 4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31 degrees 4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV + 10 degrees 9. The nickel-to-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large.Conclusions. The abundance pattern observed for CD-31 degrees 4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904 02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.},
author = {Schindewolf, Markus and Nemeth, Peter and Heber, Ulrich and Battich, Tiara and Miller Bertolami, Marcelo M. and Irrgang, Andreas and Latour, Marilyn},
doi = {10.1051/0004-6361/201732140},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;stars: atmospheres;stars: evolution;subdwarfs},
peerreviewed = {Yes},
title = {{A} quantitative {NLTE} analysis of visual and ultraviolet spectra of four helium-rich subdwarf {O} stars},
volume = {620},
year = {2018}
}
@article{faucris.246874583,
abstract = {Context. The recently claimed discovery of a massive (M-BH = 68(-13)(+11) M-circle dot) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution.Aims. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LSV +22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass.Methods. To this end, we study the spectral energy distribution of LSV +22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe.Results. Our analysis clearly shows that LSV +22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. Moreover, the elements Mg, Al, Si, S, Ar, and Fe are systematically underabundant when compared to normal main-sequence B-type stars. We suggest that LSV +22 25 is a stripped helium star and discuss two possible formation scenarios. Combining our photometric and spectroscopic results with the Gaia parallax, we infer a stellar mass of 1.1 +/- 0.5 M-circle dot. Based on the binary system's mass function, this yields a minimum mass of 2-3 M-circle dot for the compact companion, which implies that it may not necessarily be a black hole but a massive neutron- or main sequence star.Conclusions. The star LSV +22 25 has become famous for possibly having a very massive black hole companion. However, a closer look reveals that the star itself is a very intriguing object. Further investigations are necessary for complete characterization of this object.},
author = {Irrgang, Andreas and Geier, Stephan and Kreuzer, Simon and Pelisoli, Ingrid and Heber, Ulrich},
doi = {10.1051/0004-6361/201937343},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;stars: chemically peculiar;stars: early-type;pulsars: individual: LS V+22 25},
month = {Jan},
peerreviewed = {Yes},
title = {{A} stripped helium star in the potential black hole binary {LB}-1},
volume = {633},
year = {2020}
}
@article{faucris.247101655,
abstract = {Hot subdwarf B stars (sdBs) are core helium-burning stars located on the extreme horizontal branch. About half of the known sdB stars are found in close binaries. Their short orbital periods of 1.2 h to a few days suggest that they are post common-envelope systems. Eclipsing hot subdwarf binaries are rare but are important in determining the fundamental stellar parameters. Low-mass companions are identified by the reflection effect. In most cases, the companion is a main sequence star near the stellar mass limit. Here, we report the discovery of an eclipsing hot subdwarf binary SDSS J162256.66+473051.1 (J1622) with very short orbital period (0.0697 d), which has been found in the course of the MUCHFUSS project. The lightcurve shows grazing eclipses and a prominent reflection effect. An analysis of the light-and radial velocity (RV) curves indicated a mass ratio of q = 0.1325, an RV semi-amplitude K = 47.2 km s -1, and an inclination of i = 72.33°. We show that a companion mass of 0.064 MŠ(tm), which is well below the hydrogen-burning limit, is the most plausible solution, which implies a mass close to the canonical mass (0.47 MŠ(tm)) of the sdB star. Therefore, the companion is a brown dwarf, which has not only survived the engulfment by the red-giant envelope but also triggered its ejection and enabled the sdB star to form. The rotation of J1622 is expected to be tidally locked to the orbit. However, J1622 rotates too slowly (vrot = 74.5 ± 7 km≠s-1) to be synchronized, challenging tidal interaction models. © 2014 ESO.},
author = {Schaffenroth, Veronika and Geier, Stephan and Heber, Ulrich and Kupfer, Thomas and Ziegerer, Eva and Heuser, Christian and Classen, Lew and Cordes, O.},
doi = {10.1051/0004-6361/201423377},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Binaries: eclipsing; Binaries: spectroscopic; Brown dwarfs; Stars: fundamental parameters; Subdwarfs},
note = {CRIS-Team Scopus Importer:2020-12-21},
peerreviewed = {Yes},
title = {{Binaries} discovered by the {MUCHFUSS} project: {SDSS} {J162256}.66 + 473051.1: {An} eclipsing subdwarf {B} binary with a brown dwarf companion},
volume = {564},
year = {2014}
}
@article{faucris.216228190,
abstract = {Little observational data are available on the weak stellar winds of hot subdwarf stars of B spectral type (sdB). Close binary systems composed of an sdB star and a compact object (white dwarf, neutron star or black hole) could be detected as accretion-powered X-ray sources. The study of their X-ray emission can probe the properties of line-driven winds of sdB stars that cannot be derived directly from spectroscopy because of the low luminosity of these stars. Here we report on the first sensitive X-ray observations of two sdB binaries with compact companions. CD -30A degrees A 11223 is the sdB binary with the shortest known orbital period (1.2 h) and its companion is certainly a white dwarf. PG 1232-136 is an sdB binary considered the best candidate to host a black hole companion. We observed these stars with XMM-Newton in 2013 August for 50 ks and in 2009 July for 36 ks, respectively. None of them was detected and we derived luminosity upper limits of similar to 1.5 x 10(29) erg s(-1) for CD -30A degrees A 11223 and similar to 5 x 10(29) erg s(-1) for PG 1232-136. The corresponding mass-loss rate for PG 1232-136 is poorly constrained, owing to the unknown efficiency for black hole accretion. On the other hand, in the case of CD -30A degrees A 11223 we could derive, under reasonable assumptions, an upper limit of similar to 3 x 10(-13) M-aS (TM) yr(-1) on the wind mass-loss rate from the sdB star. This is one of the few observational constraints on the weak winds expected in this class of low-mass hot stars. We also report the results on the X-ray emission from a cluster of galaxies serendipitously discovered in the field of CD -30 degrees 11223.},
author = {Mereghetti, Sandro and La Palombara, Nicola and Esposito, Paolo and Gastaldello, Fabio and Tiengo, A. and Heber, Ulrich and Geier, Stephan and Wilms, Jörn},
doi = {10.1093/mnras/stu773},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {stars: individual: CD-30 11223, PG 1232-136;subdwarfs;stars: winds, outflows;X-rays: binaries;X-rays: galaxies: clusters;X-rays: individual: XMMU J141057.7-305132},
pages = {2684-2690},
peerreviewed = {Yes},
title = {{Constraints} on the winds of hot subdwarf stars from {X}-ray observations of two {sdB} binaries with compact companions: {CD}-30 degrees 11223 and {PG} 1232-136},
volume = {441},
year = {2014}
}
@article{faucris.280848628,
abstract = {Magnetic fields can play an important role in stellar evolution. Among white dwarfs, the most common stellar remnant, the fraction of magnetic systems is more than 20 per cent. The origin of magnetic fields in white dwarfs, which show strengths ranging from 40 kG to hundreds of MG, is still a topic of debate. In contrast, only one magnetic hot subdwarf star has been identified out of thousands of known systems. Hot subdwarfs are formed from binary interaction, a process often associated with the generation of magnetic fields, and will evolve to become white dwarfs, which makes the lack of detected magnetic hot subdwarfs a puzzling phenomenon. Here we report the discovery of three new magnetic hot subdwarfs with field strengths in the range 300-500 kG. Like the only previously known system, they are all helium-rich O-type stars (He-sdOs). We analysed multiple archival spectra of the three systems and derived their stellar properties. We find that they all lack radial velocity variability, suggesting formation via a merger channel. However, we derive higher than typical hydrogen abundances for their spectral type, which are in disagreement with current model predictions. Our findings suggest a lower limit to the magnetic fraction of hot subdwarfs of 0.147(+0.143)(-0.047) per cent, and provide evidence for merger-induced magnetic fields which could explain white dwarfs with field strengths of 50-150 MG, assuming magnetic flux conservation.},
author = {Pelisoli, Ingrid and Dorsch, Matti and Heber, Ulrich and Gaensicke, B. and Geier, S. and Kupfer, T. and Nemeth, P. and Scaringi, S. and Schaffenroth, },
doi = {10.1093/mnras/stac1069},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2022-08-19},
pages = {2496-2510},
peerreviewed = {Yes},
title = {{Discovery} and analysis of three magnetic hot subdwarf stars: evidence for merger-induced magnetic fields},
volume = {515},
year = {2022}
}
@article{faucris.246891335,
abstract = {Substellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star formation process. The evolution of their host stars may have an enormous impact on these small companions. Vice versa a planet might also influence stellar evolution as has recently been argued. Here, we report the discovery of an 8-23 Jupiter-mass substellar object orbiting the hot subdwarf HD 149382 in 2.391 d at a distance of only about five solar radii. Obviously, the companion must have survived engulfment in the red giant envelope. Moreover, the substellar companion has triggered envelope ejection and enabled the sdB star to form. Hot subdwarf stars have been identified as the sources of the unexpected ultraviolet (UV) emission in elliptical galaxies, but the formation of these stars is not fully understood. Being the brightest star of its class, HD 149382 offers the best conditions to detect the substellar companion. Hence, undisclosed substellar companions offer a natural solution for the long-standing formation problem of apparently single hot subdwarf stars. Planets and brown dwarfs may therefore alter the evolution of old stellar populations and may also significantly affect the UV emission of elliptical galaxies.},
author = {Geier, Stephan and Edelmann, Heinz and Heber, Ulrich and Heber, Ulrich and Morales-Rueda, L.},
doi = {10.1088/0004-637X/702/1/L96},
faupublication = {yes},
journal = {Astrophysical Journal Letters},
keywords = {binaries: spectroscopic;galaxies: evolution;planetary systems;stars: horizontal-branch;stars: individual (HD 149382);stars: low-mass, brown dwarfs},
pages = {L96-L99},
peerreviewed = {Yes},
title = {{DISCOVERY} {OF} {A} {CLOSE} {SUBSTELLAR} {COMPANION} {TO} {THE} {HOT} {SUBDWARF} {STAR} {HD} 149382-{THE} {DECISIVE} {INFLUENCE} {OF} {SUBSTELLAR} {OBJECTS} {ON} {LATE} {STELLAR} {EVOLUTION}},
volume = {702},
year = {2009}
}
@article{faucris.268936585,
abstract = {We present the discovery of a new double-detonation progenitor system consisting of a hot subdwarf B (sdB) binary with a white dwarf companion with a P (orb) = 76.34179(2) minutes orbital period. Spectroscopic observations are consistent with an sdB star during helium core burning residing on the extreme horizontal branch. Chimera light curves are dominated by ellipsoidal deformation of the sdB star and a weak eclipse of the companion white dwarf. Combining spectroscopic and light curve fits, we find a low-mass sdB star, M (sdB) = 0.383 +/- 0.028 M (circle dot) with a massive white dwarf companion, M (WD) = 0.725 +/- 0.026 M (circle dot). From the eclipses we find a blackbody temperature for the white dwarf of 26,800 K resulting in a cooling age of approximate to 25 Myr whereas our MESA model predicts an sdB age of approximate to 170 Myr. We conclude that the sdB formed first through stable mass transfer followed by a common envelope which led to the formation of the white dwarf companion approximate to 25 Myr ago. Using the MESA stellar evolutionary code we find that the sdB star will start mass transfer in approximate to 6 Myr and in approximate to 60 Myr the white dwarf will reach a total mass of 0.92 M (circle dot) with a thick helium layer of 0.17 M (circle dot). This will lead to a detonation that will likely destroy the white dwarf in a peculiar thermonuclear supernova. PTF1 J2238+7430 is only the second confirmed candidate for a double-detonation thermonuclear supernova. Using both systems we estimate that at least approximate to 1% of white dwarf thermonuclear supernovae originate from sdB+WD binaries with thick helium layers, consistent with the small number of observed peculiar thermonuclear explosions.},
author = {Kupfer, Thomas and Bauer, Evan B. and Van Roestel, Jan and Bellm, Eric C. and Bildsten, Lars and Fuller, Jim and Prince, Thomas A. and Heber, Ulrich and Geier, Stephan and Green, Matthew J. and Kulkarni, Shrinivas R. and Bloemen, Steven and Laher, Russ R. and Rusholme, Ben and Schneider, David},
doi = {10.3847/2041-8213/ac48f1},
faupublication = {yes},
journal = {Astrophysical Journal Letters},
note = {CRIS-Team WoS Importer:2022-02-04},
peerreviewed = {Yes},
title = {{Discovery} of a {Double}-detonation {Thermonuclear} {Supernova} {Progenitor}},
volume = {925},
year = {2022}
}
@article{faucris.269956340,
abstract = {Helium-rich hot subdwarf stars of spectral type O (He-sdO) are considered prime candidates for stellar merger remnants. Such events should lead to the generation of strong magnetic fields. However, no magnetic He-sdO has yet been unambiguously discovered despite the high magnetic rate (20%) among white dwarf stars, the progeny of hot subdwarfs. Here we present the discovery of a strong magnetic field (B = 353 ± 10 kG) from Zeeman-split hydrogen, helium, and metal lines in the optical X-shooter spectrum of an He-sdO and present the first spectroscopic analysis of any magnetic hot subdwarf. For this we used line-blanketed TLUSTY non-local thermodynamic equilibrium models and assumed a simple homogeneous magnetic field. The derived atmospheric parameters Teff = 44 900 ± 1000 K and log g = 5.93 ± 0.15 are typical for He-sdO stars, while the star is less hydrogen-poor than most He-sdOs at log n(He)/n(H) = + 0.28 ± 0.10. The star is a slow rotator (vrot sin i < 40 km s-1). Its chemical composition is N-rich and C- and O-poor, and the Si and S abundances are close to solar. Combining the atmospheric parameters with Gaia parallax and photometry, the stellar radius and luminosity are found to be typical for He-sdOs and place the star on the helium main sequence in the Hertzsprung-Russell diagram. Its mass of 0.93-0.30+0.44 M⊙, although uncertain, appears to be remarkably high. The strong magnetic field along with the atmospheric parameters and metal abundances provide overwhelming evidence for the double-degenerate merger scenario. },
author = {Dorsch, Matti and Reindl, N. and Pelisoli, I. and Heber, Ulrich and Geier, S. and Istrate, A. G. and Justham, S.},
doi = {10.1051/0004-6361/202142880},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Stars: early-type; Stars: magnetic field; Subdwarfs},
note = {CRIS-Team Scopus Importer:2022-02-25},
peerreviewed = {Yes},
title = {{Discovery} of a highly magnetic {He}-{sdO} star from a double-degenerate binary merger},
volume = {658},
year = {2022}
}
@article{faucris.264585741,
abstract = {Helium-burning hot subdwarf stars of spectral types O and B (sdO/B) are thought to be produced through various types of binary interactions. The helium-rich hot subdwarf star EC 22536-5304 was recently found to be extremely enriched in lead. Here, we show that EC 22536-5304 is a binary star with a metal-poor subdwarf F-type (sdF) companion. We performed a detailed analysis of high-resolution SALT/HRS and VLT/UVES spectra, deriving metal abundances for the hot subdwarf, as well as atmospheric parameters for both components. Because we consider the contribution of the sdF star, the derived lead abundance for the sdOB, + 6.3 +/- 0.3 dex relative to solar, is even higher than previously thought. We derive T-eff = 6210 +/- 70 K, log g = 4.64 +/- 0.10, [FE/H] = - 1.95 +/- 0.04, and [alpha/Fe] = + 0.40 +/- 0.04 for the sdF component. Radial velocity variations, although poorly sampled at present, indicate that the binary system has a long orbital period of about 457 days. This suggests that the system was likely formed through stable Roche lobe overflow (RLOF). A kinematic analysis shows that EC 22536-5304 is on an eccentric orbit around the Galactic centre. This, as well as the low metallicity and strong alpha enhancement of the sdF-type companion, indicate that EC 22536-5304 is part of the Galactic halo or metal-weak thick disc. As the first long-period hot subdwarf binary at [FE/H] less than or similar to- 1, EC 22536-5304 may help to constrain the RLOF mechanism for mass transfer from low-mass, low-metallicity red giant branch (RGB) stars to main-sequence companions.},
author = {Dorsch, Matti and Jeffery, C. S. and Irrgang, Andreas and Woolf, V. and Heber, Ulrich},
doi = {10.1051/0004-6361/202141381},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
note = {CRIS-Team WoS Importer:2021-10-01},
peerreviewed = {Yes},
title = {{EC} 22536-5304: a lead-rich and metal-poor long-period binary},
volume = {653},
year = {2021}
}
@article{faucris.263750201,
abstract = {We present time-series spectroscopy and photometry of Gaia DR2 6097540197980557440, a new deeply eclipsing hot subdwarf B (sdB) + M dwarf (dM) binary. We discovered this object during the course of the Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project, which aims to find new eclipsing sdB+dM binaries (HW Vir systems) and increase the small sample of studied systems. In addition to the primary eclipse, which is in excess of similar to 5 mag in the optical, the light curve also shows features typical for other HW Vir binaries such as a secondary eclipse and strong reflection effect from the irradiated, cool companion. The orbital period is 0.127037 days (similar to 3 hr), falling right at the peak of the orbital period distribution of known HW Vir systems. Analysis of our time-series spectroscopy yields a radial velocity semiamplitude of K (sdB) = 100.0 +/- 2.0 km s(-1), which is among the fastest line-of-sight velocities found to date for an HW Vir binary. State-of-the-art atmospheric models that account for deviations from local thermodynamic equilibrium are used to determine the atmospheric parameters of the sdB. Although we cannot claim a unique light-curve modeling solution, the best-fitting model has an sdB mass of M (sdB) = 0.47 +/- 0.03 M (circle dot) and a companion mass of M (dM) = 0.18 +/- 0.01 M (circle dot). The radius of the companion appears to be inflated relative to theoretical mass-radius relationships, consistent with other known HW Vir binaries. Additionally, the M dwarf is one of the most massive found to date among this type of binary.},
author = {Corcoran, Kyle A. and Barlow, Brad N. and Schaffenroth, Veronika and Heber, Ulrich and Walser, Stephen and Irgang, Andreas},
doi = {10.3847/1538-4357/ac0ae5},
faupublication = {yes},
journal = {Astrophysical Journal},
note = {CRIS-Team WoS Importer:2021-09-10},
peerreviewed = {Yes},
title = {{Eclipsing} {Binaries} {Found} by the {EREBOS} {Project}: {Gaia} {DR2} 6097540197980557440-a {Deeply} {Eclipsing} {sdB} plus {dM} {System}},
volume = {918},
year = {2021}
}
@inproceedings{faucris.246889481,
abstract = {HD188112 is an extremely low mass white dwarf in a close binary system. According to a previous study, the mass of HD188112 is similar to 0.24 M-circle dot and a lower limit of 0.73 M-circle dot could be put for the mass of its unseen companion, a compact degenarate object. We used HST STIS spectra to measure the rotational broadening of UV metallic lines in HD188112, in order to put tighter constraints on the mass of its companion. By assuming that the system in is synchronous rotation, we derive a companion mass between 1.05 and 1.25 M-circle dot. We also measure abundances for magnesium, silicon, and iron, respectively log N(X)/N(H) = -6.40, -7.25, and -5.81. The radial velocities measured from the UV spectra are found to be in very good agreement with the prediction based on the orbital parameters derived in the previous study made a decade ago.},
author = {Latour, Marilyn and Irrgang, Andreas and Heber, Ulrich and Schaffenroth, Veronika},
faupublication = {yes},
month = {Jan},
pages = {9-14},
peerreviewed = {unknown},
publisher = {ASTRONOMICAL SOC PACIFIC, 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA},
title = {{HD188112}: {Supernova} {Ia} {Progenitor}?},
volume = {493},
year = {2015}
}
@article{faucris.227512461,
abstract = {The intermediate He-enriched hot subdwarf star Feige 46 was recently reported as the second member of the V366 Aqr (or He-sdOBV) pulsating class. Feige 46 is very similar to the prototype of the class, LS IV-14 degrees 116, not only in terms of pulsational properties, but also in terms of atmospheric parameters and kinematic properties. LS IV-14 degrees 116 is additionally characterized by a very peculiar chemical composition, with extreme overabundances of the trans-iron elements Ge, Sr, Y, and Zr. We investigate the possibility that the similarity between the two pulsators extends to their chemical composition. We retrieved archived optical and UV spectroscopic observations of Feige 46 and performed an abundance analysis using model atmospheres and synthetic spectra computed with TLUSTY and SYNSPEC. In total, we derived abundances for 16 elements and provide upper limits for four additional elements. Using absorption lines in the optical spectrum of the star we measure an enrichment of more than 10 000x solar for yttrium and zirconium. The UV spectrum revealed that strontium is equally enriched. Our results confirm that Feige 46 is not only a member of the now growing group of heavy metal subdwarfs, but also has an abundance pattern that is remarkably similar to that of LS IV-14 degrees 116.},
author = {Latour, M. and Dorsch, M. and Heber, Ulrich},
doi = {10.1051/0004-6361/201936247},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;subdwarfs;stars: individual: Feige 46},
note = {CRIS-Team WoS Importer:2019-10-04},
peerreviewed = {Yes},
title = {{Heavy} metal enrichment in the intermediate {He}-{sdOB} pulsator {Feige} 46},
volume = {629},
year = {2019}
}
@article{faucris.246880592,
abstract = {The intermediate He-enriched hot subdwarf star Feige 46 was recently reported as the second member of the V366 Aqr (or He-sdOBV) pulsating class. Feige 46 is very similar to the prototype of the class, LS IV-14 degrees 116, not only in terms of pulsational properties, but also in terms of atmospheric parameters and kinematic properties. LS IV-14 degrees 116 is additionally characterized by a very peculiar chemical composition, with extreme overabundances of the trans-iron elements Ge, Sr, Y, and Zr. We investigate the possibility that the similarity between the two pulsators extends to their chemical composition. We retrieved archived optical and UV spectroscopic observations of Feige 46 and performed an abundance analysis using model atmospheres and synthetic spectra computed with TLUSTY and SYNSPEC. In total, we derived abundances for 16 elements and provide upper limits for four additional elements. Using absorption lines in the optical spectrum of the star we measure an enrichment of more than 10 000x solar for yttrium and zirconium. The UV spectrum revealed that strontium is equally enriched. Our results confirm that Feige 46 is not only a member of the now growing group of heavy metal subdwarfs, but also has an abundance pattern that is remarkably similar to that of LS IV-14 degrees 116.},
author = {Latour, Marilyn and Dorsch, Matti and Heber, Ulrich},
doi = {10.1051/0004-6361/201936247},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;subdwarfs;stars: individual: Feige 46},
peerreviewed = {Yes},
title = {{Heavy} metal enrichment in the intermediate {He}-{sdOB} pulsator {Feige} 46},
volume = {629},
year = {2019}
}
@article{faucris.246880860,
abstract = {Context. Hot subluminous stars can be spectroscopically classified as subdwarf B (sdB) and O (sdO) stars. While the latter are predominantly hydrogen deficient, the former are mostly helium deficient. The atmospheres of most sdOs are almost devoid of hydrogen, whereas a small group of hot subdwarf stars of mixed H/He composition exists, showing extreme metal abundance anomalies. Whether such intermediate helium-rich (iHe) subdwarf stars provide an evolutionary link between the dominant classes is an open question.Aims. The presence of strong Ge, Sn, and Pb lines in the UV spectrum of HZ44 suggests a strong enrichment of heavy elements in this iHe-sdO star and calls for a detailed quantitative spectral analysis focusing on trans-iron elements.Methods. Non-local thermodynamical equilibrium model atmospheres and synthetic spectra calculated with TLUSTY/SYNSPEC were combined with high-quality optical, ultraviolet (UV), and far-UV (FUV) spectra of HZ44 and its hotter sibling HD127493 to determine their atmospheric parameters and metal abundance patterns.Results. By collecting atomic data from the literature we succeeded in determining the abundances of 29 metals in HZ44, including the trans-iron elements Ga, Ge, As, Se, Zr, Sn, and Pb and providing upper limits for ten other metals. This makes it the best-described hot subdwarf in terms of chemical composition. For HD127493 the abundance of 15 metals, including Ga, Ge, and Pb and upper limits for another 16 metals were derived. Heavy elements turn out to be overabundant by one to four orders of magnitude with respect to the Sun. Zr and Pb are among the most enriched elements.Conclusions. The C, N, and O abundance for both stars can be explained by the nucleosynthesis of hydrogen burning in the CNO cycle along with the stars' helium enrichment. On the other hand, the heavy-element anomalies are unlikely to be caused by nucleosynthesis. Instead diffusion processes are evoked, with radiative levitation overcoming gravitational settlement of the heavy elements.},
author = {Dorsch, Matti and Latour, Marilyn and Heber, Ulrich},
doi = {10.1051/0004-6361/201935724},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;stars: atmospheres;stars: individual: HZ 44;stars: individual: HD 127493;stars: evolution;subdwarfs},
peerreviewed = {Yes},
title = {{Heavy} metals in intermediate {He}-rich hot subdwarfs: the chemical composition of {HZ44} and {HD127493}},
volume = {630},
year = {2019}
}
@article{faucris.228156245,
abstract = {Context. Hot subluminous stars can be spectroscopically classified as subdwarf B (sdB) and O (sdO) stars. While the latter are predominantly hydrogen deficient, the former are mostly helium deficient. The atmospheres of most sdOs are almost devoid of hydrogen, whereas a small group of hot subdwarf stars of mixed H/He composition exists, showing extreme metal abundance anomalies. Whether such intermediate helium-rich (iHe) subdwarf stars provide an evolutionary link between the dominant classes is an open question. Aims. The presence of strong Ge, Sn, and Pb lines in the UV spectrum of HZ 44 suggests a strong enrichment of heavy elements in this iHe-sdO star and calls for a detailed quantitative spectral analysis focusing on trans-iron elements. Methods. Non-local thermodynamical equilibrium model atmospheres and synthetic spectra calculated with TLUSTY/SYNSPEC were combined with high-quality optical, ultraviolet (UV), and far-UV (FUV) spectra of HZ 44 and its hotter sibling HD 127493 to determine their atmospheric parameters and metal abundance patterns. Results. By collecting atomic data from the literature we succeeded in determining the abundances of 29 metals in HZ 44, including the trans-iron elements Ga, Ge, As, Se, Zr, Sn, and Pb and providing upper limits for ten other metals. This makes it the best-described hot subdwarf in terms of chemical composition. For HD 127493 the abundance of 15 metals, including Ga, Ge, and Pb and upper limits for another 16 metals were derived. Heavy elements turn out to be overabundant by one to four orders of magnitude with respect to the Sun. Zr and Pb are among the most enriched elements. Conclusions. The C, N, and O abundance for both stars can be explained by the nucleosynthesis of hydrogen burning in the CNO cycle along with the stars' helium enrichment. On the other hand, the heavy-element anomalies are unlikely to be caused by nucleosynthesis. Instead diffusion processes are evoked, with radiative levitation overcoming gravitational settlement of the heavy elements.},
author = {Dorsch, Matti and Latour, M. and Heber, Ulrich},
doi = {10.1051/0004-6361/201935724},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Stars: abundances; Stars: atmospheres; Stars: evolution; Stars: individual: HD 127493; Stars: individual: HZ 44; Subdwarfs},
note = {CRIS-Team Scopus Importer:2019-10-22},
peerreviewed = {Yes},
title = {{Heavy} metals in intermediate {He}-rich hot subdwarfs: {The} chemical composition of {HZ} 44 and {HD} 127493},
volume = {630},
year = {2019}
}
@article{faucris.228300265,
abstract = {HD4539 (alias PG0044 + 097 or EPIC 220641886) is a bright (V = 10.2) long-period V1093 Her-type subdwarf B (sdB) pulsating star that was observed by the Kepler spacecraft in its secondary (K2) mission. We use the K2 light curve (78.7 d) to extract 169 pulsation frequencies, 124 with a robust detection. Most of these frequencies are found in the low-frequency region typical of gravity (g-)modes, but some higher frequencies corresponding to pressure (p-)modes are also detected. Therefore HD4539 is a hybrid pulsator and both the deep and surface layers of the star can potentially be probed through asteroseismology. The lack of any frequency splitting in its amplitude spectrum suggests that HD 4539 has a rotation period longer than the K2 run and/or that it is seen pole-on. From asymptotic period spacing we see many high-degree modes, up to l = 12, in the spectrum of HD 4539, with amplitudes as low as a few ppm. A large fraction of these modes can be identified and for similar to 29 per cent of them we obtain a unique and robust identification corresponding to l <= 8. Our study includes also a new determination of the atmospheric parameters of the star. From low-resolution spectroscopy we obtain T-eff = 22 800 +/- 160 K, log g = 5.20 +/- 0.02, and log(N(He)/N(H)) = -2.34 +/- 0.05. By fitting the SED we obtain T-eff = 23 470(-210)(+650) K, R-star = 0.26 +/- 0.01 R-circle dot, and M-star = 0.40 +/- 0.08 M-circle dot. Moreover, from 11 high-resolution spectra we see the radial velocity variations caused by the stellar pulsations, with amplitudes of approximate to 150 m s(-1) for the main modes, and we can exclude the presence of a companion with a minimum mass higher than a few Jupiter masses for orbital periods below similar to 300 d.},
author = {Silvotti, R. and Uzundag, M. and Baran, A. S. and Ostensen, R. H. and Telting, J. H. and Heber, Ulrich and Reed, M. D. and Vuckovic, M.},
doi = {10.1093/mnras/stz2244},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2019-10-25},
pages = {4791-4801},
peerreviewed = {Yes},
title = {{High}-degree gravity modes in the single {sdB} star {HD} 4539},
volume = {489},
year = {2019}
}
@article{faucris.246889737,
abstract = {The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M > 1.0 M-circle dot), neutron stars, or stellar-mass black holes. The existence of such systems is predicted by binary evolution theory, and recent discoveries indicate that they exist in our Galaxy. We present orbital and atmospheric parameters and put constraints on the nature of the companions of 12 close hot subdwarf B star (sdB) binaries found in the course of the MUCHFUSS project. The systems show periods between 0.14 and 7.4 days. In nine cases the nature of the companions cannot be constrained unambiguously whereas three systems most likely have white dwarf companions. We find that the companion to SDSS J083006.17+475150.3 is likely to be a rare example of a low-mass helium-core white dwarf. SDSS J095101.28+034757.0 shows an excess in the infrared that probably originates from a third companion in a wide orbit, which makes this system the second candidate hierarchical triple system containing an sdB star. SDSS J113241.58-063652.8 is the first helium deficient sdO star with a confirmed close companion. This study brings to 142 the number of sdB binaries with orbital periods of less than 30 days and with measured mass functions. We present an analysis of the minimum companion mass distribution and show that it is bimodal. One peak around 0.1 M-circle dot corresponds to the low-mass main sequence (dM) and substellar companions. The other peak around 0.4 M-circle dot corresponds to the white dwarf companions. The derived masses for the white dwarf companions are significantly lower than the average mass for single carbon-oxygen white dwarfs. In a T-eff - log g diagram of sdB+dM companions, we find signs that the sdB components are more massive than the rest of the sample. The full sample was compared to the known population of extremely low-mass white dwarf binaries as well as short-period white dwarfs with main sequence companions. Both samples show a significantly different companion mass distribution indicating either different selection effects or different evolutionary paths. We identified 16 systems where the dM companion will fill its Roche Lobe within a Hubble time and will evolve into a cataclysmic variable; two of them will have a brown dwarf as donor star. Twelve systems with confirmed white dwarf companions will merge within a Hubble time, two of them having a mass ratio to evolve into a stable AMCVn-type binary and another two which are potential supernova Ia progenitor systems. The remaining eight systems will most likely merge and form RCrB stars or massive C/O white dwarfs depending on the structure of the white dwarf companion.},
author = {Kupfer, Thomas and Geier, S. and Heber, Ulrich and Ostensen, R. H. and Barlow, B. N. and Maxted, P. F. L. and Heuser, Christian and Schaffenroth, Veronika and Gaensicke, B. T.},
doi = {10.1051/0004-6361/201425213},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {subdwarfs;binaries: close},
peerreviewed = {Yes},
title = {{Hot} subdwarf binaries from the {MUCHFUSS} project {Analysis} of 12 new systems and a study of the short-period binary population},
volume = {576},
year = {2015}
}
@inproceedings{faucris.246886957,
abstract = {Hot subdwarf stars (sdO/Bs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. They constitute the dominant population of UV-bright stars in old stellar environments and are most likely formed by binary interactions. We perform the first systematic, spectroscopic analysis of a sample of those stars in the Galactic halo based on data from SDSS. In the course of this project we discovered 177 close binary candidates. A significant fraction of the sdB binaries turned out to have close substellar companions, which shows that brown dwarfs and planets can significantly influence late stellar evolution. Close hot subdwarf binaries with massive white dwarf companions on the other hand are good candidates for the progenitors of type Ia supernovae. We discovered a hypervelocity star, which not only turned out to be the fastest unbound star known in our Galaxy, but also the surviving companion of such a supernova explosion.},
author = {Geier, Stephan and Kupfer, Thomas and Schaffenroth, Veronika and Heber, Ulrich},
doi = {10.1017/S174392131500681X},
faupublication = {yes},
keywords = {binaries: spectroscopic;binaries: eclipsing;stars: subdwarfs;stars: brown dwarfs},
month = {Jan},
pages = {302-303},
peerreviewed = {unknown},
title = {{Hot} subdwarf stars in the {Galactic} halo {Tracers} of prominent events in late stellar evolution},
volume = {11},
year = {2016}
}
@article{faucris.246887228,
abstract = {Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters omega Cen and NGC. 2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US. 708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HW. Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HW. Vir systems from eclipse timings. The high incidence of circumbinary substellar objects suggests that most of the planets are formed from the remaining CE material (second generation planets). Several types of pulsating star have been discovered among hot subdwarf stars, the most common are the gravity-mode sdB pulsators (V1093 Her) and their hotter siblings, the p-mode pulsating V361 Hya stars. Another class of multi-periodic pulsating hot subdwarfs has been found in the globular cluster omega Cen that is unmatched by any field star. Asteroseismology has advanced enormously thanks to the high-precision Kepler photometry and allowed stellar rotation rates to be determined, the interior structure of gravity-mode pulsators to be probed and stellar ages to be estimated. Rotation rates turned out to be unexpectedly slow calling for very efficient angular momentum loss on the red giant branch or during the helium core flash. The convective cores were found to be larger than predicted by standard stellar evolution models requiring very efficient angular momentum transport on the red giant branch. The masses of hot subdwarf stars, both single or in binaries, are the key to understand the stars' evolution. A few pulsating sdB stars in eclipsing binaries have been found that allow both techniques to be applied for mass determination. The results, though few, are in good agreement with predictions from binary population synthesis calculations. New classes of binaries, hosting so-called extremely low mass (ELM) white dwarfs (M < 0.3 M-circle dot), have recently been discovered, filling a gap in the mosaic of binary stellar evolution. Like most sdB stars the ELM white dwarfs are the stripped cores of red giants, the known companions are either white dwarfs, neutron stars (pulsars) or F-or A-type main sequence stars ("EL CVn" stars). In the near future, the Gaia mission will provide high-precision astrometry for a large sample of subdwarf stars to disentangle the different stellar populations in the field and to compare the field subdwarf population with the globular clusters' hot subdwarfs. New fast-moving subdwarfs will allow the mass of the Galactic dark matter halo to be constrained and additional unbound hyper-velocity stars may be discovered.},
author = {Heber, Ulrich and Heber, Ulrich},
doi = {10.1088/1538-3873/128/966/082001},
faupublication = {yes},
journal = {Publications of the Astronomical Society of the Pacific},
keywords = {binaries: close;stars: abundances;stars: evolution;stars: oscillations;subdwarfs;white dwarfs},
peerreviewed = {Yes},
title = {{Hot} {Subluminous} {Stars}},
volume = {128},
year = {2016}
}
@article{faucris.246875118,
abstract = {The hypervelocity star (HVS) survey conducted at the Multiple Mirror Telescope (MMT) identified 42 B-type stars in the Galactic halo whose radial velocity in the Galactic rest-frame exceeds +275 km s 1. In order to unravel the nature and origin of those highvelocity outliers, their complete six-dimensional phase space information is needed. To this end, we complemented positions and proper motions from the second data release of Gaia with revised radial velocities and spectrophotometric distances that are based on a reanalysis of the available MMT spectra of 40 objects using state-of-the-art model spectra and a tailored analysis strategy. The resulting position and velocity vectors for 37 stars were then used as input for a subsequent kinematic investigation to obtain as complete a picture as possible. The combination of projected rotational velocity, position in the Kiel diagram, and kinematic properties suggests that all objects in the sample except two (B576, B598) are very likely to be main sequence stars. While the available data are still not precise enough to constrain the place of origin for 19 program stars, we identified eight objects that either come from the outer rim of the Galactic disk or not from the disk at all, along with ten that presumably stem from the Galactic disk. For almost all of those 18 targets with more or less well-constrained spatial origin, the Galactic center (GC) is disqualified as a possible place of origin. The most notable exception is B576, the origin of which coincides extremely well with the GC when assuming a blue horizontal branch nature for it. HVS 22 is by far the most extreme object in the sample. Although its origin is completely unconstrained, an ejection from the GC by the Hills mechanism is the most plausible explanation for its current Galactic rest-frame velocity of 1530(-560)(+690) km s(-1).},
author = {Kreuzer, Simon and Irrgang, Andreas and Heber, Ulrich},
doi = {10.1051/0004-6361/202037747},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: distances;stars: early-type;stars: fundamental parameters;stars: kinematics and dynamics},
peerreviewed = {Yes},
title = {{Hypervelocity} stars in the {Gaia} era {Revisiting} the most extreme stars from the {MMT} {HVS} survey},
volume = {637},
year = {2020}
}
@article{faucris.246881708,
abstract = {Context. Young massive stars in the halo are assumed to be runaway stars from the Galactic disk. Possible ejection scenarios are binary supernova ejections (BSE) or dynamical ejections from star clusters (DE). Hypervelocity stars (HVSs) are extreme runaway stars that are potentially unbound from the Galaxy. Powerful acceleration mechanisms such as the tidal disruption of a binary system by a supermassive black hole (SMBH) are required to produce them. Therefore, HVSs are believed to originate in the Galactic center (GC), the only place known to host an SMBH.Aims. The second Gaia data release (DR2) offers the opportunity of studying HVSs in an unprecedented manner. We revisit some of the most interesting high-velocity stars, that is, 15 stars (11 candidate HVSs and 4 radial velocity outliers) for which proper motions with the Hubble Space Telescope. were obtained in the pre-Gaia era, to unravel their origin.Methods. By carrying out kinematic analyses based on revised spectrophotometric distances and proper motions from Gaia DR2, kinematic properties were obtained that help constrain the spatial origins of these stars.Results. Stars that were previously considered (un)bound remain (un)bound in Galactic potentials favored by Gaia DR2 astrometry. For nine stars (five candidate HVSs plus all four radial velocity outliers), the GC can be ruled out as spatial origin at least at 2 sigma confidence level, suggesting that a large portion of the known HVSs are disk runaway stars launched close to or beyond Galactic escape velocities. The fastest star in the sample, HVS 3, is confirmed to originate in the Large Magellanic Cloud.Conclusions. Because the ejection velocities of five of our non-GC stars are close to or above the upper limits predicted for BSE and DE, another powerful dynamical ejection mechanism (e.g., involving massive perturbers such as intermediate-mass black holes) is likely to operate in addition to the three classical scenarios mentioned above.},
author = {Irrgang, Andreas and Kreuzer, Simon and Heber, Ulrich},
doi = {10.1051/0004-6361/201833874},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: early-type;stars: kinematics and dynamics},
peerreviewed = {Yes},
title = {{Hypervelocity} stars in the {Gaia} era {Runaway} {B} stars beyond the velocity limit of classical ejection mechanisms},
volume = {620},
year = {2018}
}
@article{faucris.111867184,
abstract = {Studying atmospheric neutrino oscillations in the few-GeV range with a multimegaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1-20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ic},
author = {Adrian-Martinez, S. and Ageron, M. and Aiello, S. and Albert, A. and Ameli, F. and Anassontzis, E. G. and Andre, Michel and Androulakis, G. and Anghinolfi, M. and Anton, Gisela and Ardid, M. and Avgitas, T. and Barbarino, G. and Barbarito, E. and Baret, B. and Barrios-Marti, J. and Belias, A. and Berbee, E. and Van Den Berg, A. and Bertin, V. and Beurthey, S. and Van Beveren, V. and Beverini, N. and Biagi, S. and Biagioni, A. and Billault, M. and Bondi, M. and Bormuth, R. and Bouhadef, B. and Bourlis, G. and Bourret, S. and Boutonnet, C. and Bouwhuis, M. and Bozza, C. and Bruijn, R. and Brunner, J. and Buis, E. and Buompane, Raffaele and Busto, J. and Cacopardo, G. and Caillat, L. and Calamai, M. and Calvo, D. and Capone, Antonio and Caramete, L. and Cecchini, S. and Celli, S. and Champion, C. and Cherubini, S. and Chiarella, V. and Chiarelli, L. and Chiarusi, T. and Circella, M. and Classen, Lew and Cobas, D. and Cocimano, R. and Coelho, J. A. B. and Coleiro, A. and Colonges, S. and Coniglione, R. and Cordelli, M. and Cosquer, A. and Coyle, P. and Creusot, A. and Cuttone, Giacomo and D'Amato, C. and D'Amico, A. and D'Onofrio, A. and De Bonis, G. and De Sio, C. and Di Palma, I. and Diaz, A. F. and Distefano, C. and Donzaud, C. and Dornic, D. and Dorosti-Hasankiadeh, Q. and Drakopoulou, E. and Drouhin, D. and Durocher, M. and Eberl, Thomas and Eichie, Sebastian and Van Eijk, D. and El Bojaddaini, I. and Elsaesser, D. and Enzenhofer, A. and Favaro, M. and Fermani, P. and Ferrara, G. and Frascadore, G. and Furini, M. and Fusco, L. A. and Gál, Tamás and Galata, S. and Garufi, F. and Gay, P. and Gebyehu, M. and Giacomini, F. and Gialanella, L. and Giordano, V. and Gizani, N. and Gracia, R. and Graf, Kay and Gregoire, T. and Grella, G. and Grmek, A. and Guerzoni, M. and Habel, R. and Hallmann, Steffen and Van Haren, H. and Harissopulos, S. and Heid, Thomas and Heijboer, A. and Heine, E. and Henry, S. and Hernandez-Rey, J. J. and Hevinga, M. and Hofestädt, Jannik and Hugon, C. M. F. and Illuminati, G. and James, Clancy and Jansweijer, P. and Jongen, M. and De Jong, M. and Kadler, M. and Kalekin, O. and Kappes, A. and Katz, Uli and Keller, P. and Kieft, G. and Kießling, Dominik and Koffeman, E. N. and Kooijman, P. and Kouchner, A. and Kreter, M. and Kulikovskiy, V. and Lahmann, Robert and Lamare, P. and Larosa, G. and Leisos, A. and Leone, F. and Leonora, E. and Clark, M. Lindsey and Liolios, A. and Llorens Alvarez, C. D. and Lo Presti, D. and Lohner, H. and Lonardo, A. and Lotze, M. and Loucatos, S. and Maccioni, E. and Mannheim, K. and Manzali, M. and Margiotta, A. and Margotti, A. and Marinelli, A. and Maris, O. and Markou, C. and Martinez-Mora, J. A. and Martini, A. and Marzaioli, F. and Mele, R. and Melis, K. W. and Michael, T. and Migliozzi, P. and Migneco, E. and Mijakowski, P. and Miraglia, A. and Mollo, C. M. and Mongelli, M. and Morganti, M. and Moussa, A. and Musico, P. and Musumeci, M. and Navas, Sergio and Nicolau, C. A. and Olcina, I. and Olivetto, C. and Orlando, A. and Orzelli, A. and Pancaldi, G. and Papaikonomou, A. and Papaleo, R. and Pavalas, G. E. and Peek, H. and Pellegrini, G. and Pellegrino, C. and Perrina, C. and Pfutzner, M. and Piattelli, P. and Pikounis, K. and Pleinert, Marc-Oliver and Poma, G. E. and Popa, V. and Pradier, T. and Pratolongo, F. and Puehlhofer, G. and Pulvirenti, S. and Quinn, L. and Racca, C. and Raffaelli, F. and Randazzo, N. and Rauch, Thomas and Real, D. and Resvanis, L. and Reubelt, Jonas and Riccobene, Giorgio Maria and Rossi, C. and Rovelli, A. and Saldana, M. and Salvadori, I. and Samtleben, D. F. E. and Garcia, A. Sanchez and Losa, A. Sanchez and Sanguineti, Matteo and Santangelo, A. and Santonocito, D. and Sapienza, P. and Schimmel, F. and Schmelling, J. and Schnabel, Jutta and Sciacca, Virginia and Sedita, M. and Seitz, Thomas and Sgura, I. and Simeone, F. and Sipala, V. and Spisso, B. and Spurio, M. and Stavropoulos, G. and Steijger, J. and Stellacci, S. M. and Stransky, Dominik and Taiuti, M. and Tayalati, Y. and Terrasi, F. and Tezier, D. and Theraube, S. and Timmer, P. and Tonnis, C. and Trasatti, L. and Travaglini, R. and Trovato, Agata and Tsirigotis, A. and Tzamarias, S. and Tzamariudaki, E. and Vallage, B. and Van Elewyck, V. and Vermeulen, J. and Versari, F. and Vicini, P. and Viola, Salvatore and Vivolo, D. and Volkert, Marco and Wiggers, L. and Wilms, Jörn and De Wolf, E. and Zachariadou, K. and Zani, S. and Zornoza, J. D. and Zuniga, J.},
doi = {10.1007/JHEP05(2017)008},
faupublication = {yes},
journal = {Journal of High Energy Physics},
keywords = {Neutrino Detectors and Telescopes (experiments)},
peerreviewed = {Yes},
title = {{Intrinsic} limits on resolutions in muon- and electron-neutrino charged-current events in the {KM3NeT}/{ORCA} detector},
year = {2017}
}
@article{faucris.269468399,
abstract = {Context. Kinematic and chemical tagging of stellar populations have both revealed much information on the past and recent history of the Milky Way, including its formation history, merger events, and mixing of populations across the Galactic disk and halo.},
author = {Raddi, Roberto and Torres, Santiago and Rebassa-Mansergas, Alberto and Maldonado, Jesus and Camisassa, Maria E. and Koester, Detlev and Fusillo, Nicola Pietro Gentile and Tremblay, Pier-Emmanuel and Dimpel, Markus and Heber, Ulrich and Cunningham, Tim and Ren, Juan-Juan},
doi = {10.1051/0004-6361/202141837},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
month = {Jan},
note = {CRIS-Team WoS Importer:2022-02-11},
peerreviewed = {Yes},
title = {{Kinematic} properties of white dwarfs {Galactic} orbital parameters and age-velocity dispersion relation},
volume = {658},
year = {2022}
}
@article{faucris.106287324,
abstract = {The main objectives of the KM3NeT Collaboration are (i) the discovery and subsequent observation of high-energy neutrino sources in the Universe and (ii) the determination of the mass hierarchy of neutrinos. These objectives are strongly motivated by two recent important discoveries, namely: (1) the high-energy astrophysical neutrino signal reported by IceCube and (2) the sizable contribution of electron neutrinos to the third neutrino mass eigenstate as reported by Daya Bay, Reno and others. To meet these objectives, the KM3NeT Collaboration plans to build a new Research Infrastructure consisting of a network of deep-sea neutrino telescopes in the Mediterranean Sea. A phased and distributed implementation is pursued which maximises the access to regional funds, the availability of human resources and the synergistic opportunities for the Earth and sea sciences community. Three suitable deep-sea sites are selected, namely off-shore Toulon (France), Capo Passero (Sicily, Italy) and Pylos (Peloponnese, Greece). The infrastructure will consist of three so-called building blocks. A building block comprises 115 strings, each string comprises 18 optical modules and each optical module comprises 31 photo-multiplier tubes. Each building block thus constitutes a three-dimensional array of photo sensors that can be used to detect the Cherenkov light produced by relativistic particles emerging from neutrino interactions. Two building blocks will be sparsely configured to fully explore the IceCube signal with similar instrumented volume, different methodology, improved resolution and complementary field of view, including the galactic plane. One building block will be densely configured to precisely measure atmospheric neutrino oscillations.},
author = {Adrian-Martinez, S. and Ageron, M. and Aharonian, F. and Aiello, S. and Albert, A. and Ameli, F. and Anassontzis, E. and Andre, Michel and Androulakis, G. and Anghinolfi, M. and Anton, Gisela and Ardid, Miguel and Avgitas, T. and Barbarino, G. and Barbarito, E. and Baret, B. and Barrios-Marti, J. and Belhorma, B. and Belias, A. and Berbee, E. and Van Den Berg, A. and Bertin, V. and Beurthey, S. and Van Beveren, V. and Beverini, Nicolo and Biagi, Simone and Biagioni, Andrea and Billault, M. and Bondi, M. and Bormuth, R. and Bouhadef, B. and Bourlis, G. and Bourret, S. and Boutonnet, C. and Bouwhuis, M. and Bozza, C. and Bruijn, R. and Brunner, J. and Buis, E. and Busto, J. and Cacopardo, G. and Caillat, L. and Calamai, M. and Calvo, D. and Capone, Antonio and Caramete, Laurentiu and Cecchini, S. and Celli, Silvia and Champion, C. and Cherkaoui El Moursli, R. and Cherubini, Silvio and Chiarusi, T. and Circella, M. and Classen, Lew and Cocimano, R. and Coelho, J. A. B. and Coleiro, Alexis and Colonges, S. and Coniglione, R. and Cordelli, M. and Cosquer, A. and Coyle, P. and Creusot, A. and Cuttone, Giacomo and D'Amico, A. and De Bonis, G. and De Rosa, Gianfranca and De Sio, C. and Di Capua, F. and Di Palma, Irene and Diaz Garcia, A. F. and Distefano, Carla and Donzaud, C. and Dornic, D. and Dorosti-Hasankiadeh, Q. and Drakopoulou, E. and Drouhin, D. and Drury, L. and Durocher, M. and Eberl, Thomas and Eichie, Sebastian and Van Eijk, D. and El Bojaddaini, I. and El Khayati, N. and Elsaesser, D. and Enzenhofer, A. and Fassi, Farida and Favali, P. and Fermani, Paolo and Ferrara, G. and Filippidis, C. and Frascadore, G. and Fusco, L. A. and Gál, Tamás and Galata, S. and Garufi, Fabio and Gay, P. and Gebyehu, M. and Giordano, Valentina and Gizani, N. and Gracia, R. and Graf, Kay and Gregoire, T. and Grella, G. and Habel, R. and Hallmann, Steffen and Van Haren, H. and Harissopulos, Sotirios and Heid, Thomas and Heijboer, A. and Heine, E. and Henry, S. and Hernandez-Rey, J. J. and Hevinga, M. and Hofestädt, Jannik and Hugon, C. M. F. and Illuminati, G. and James, Clancy and Jansweijer, P. and Jongen, M. and De Jong, M. and Kadler, Matthias and Kalekin, O. and Kappes, Alexander and Katz, Uli and Keller, P. and Kieft, G. and Kießling, Dominik and Koffeman, E. N. and Kooijman, P. and Kouchner, A. and Kulikovskiy, V. and Lahmann, Robert and Lamare, P. and Leisos, A. and Leonora, E. and Clark, M. Lindsey and Liolios, A. and Llorens Alvarez, C. D. and Lo Presti, Domenico and Lohner, H. and Lonardo, A. and Lotze, M. and Loucatos, S. and Maccioni, E. and Mannheim, K. and Margiotta, A. and Marinelli, A. and Maris, O. and Markou, C. and Martinez-Mora, J. A. and Martini, A. and Mele, R. and Melis, K. W. and Michael, T. and Migliozzi, Pasquale and Migneco, E. and Mijakowski, P. and Miraglia, A. and Mollo, C. M. and Mongelli, M. and Morganti, M. and Moussa, A. and Musico, P. and Musumeci, M. and Navas, Sergio and Nicolau, C. A. and Olcina, I. and Olivetto, C. and Orlando, Angelo and Papaikonomou, A. and Papaleo, R. and Pavalas, G. E. and Peek, H. and Pellegrino, Carmelo and Perrina, C. and Pfutzner, M. and Piattelli, Paolo and Pikounis, K. and Poma, G. E. and Popa, V. and Pradier, Thierry and Pratolongo, F. and Puehlhofer, G. and Pulvirenti, S. and Quinn, L. and Racca, C. and Raffaelli, F. and Randazzo, N. and Rapidis, P. and Razis, P. and Real, D. and Resvanis, L. and Reubelt, Jonas and Riccobene, Giorgio Maria and Rossi, C. and Rovelli, A. and Saldana, M. and Salvadori, I. and Samtleben, D. F. E. and Garcia, A. Sanchez and Losa, A. Sanchez and Sanguineti, Matteo and Santangelo, A. and Santonocito, D. and Sapienza, P. and Schimmel, F. and Schmelling, J. and Sciacca, Virginia and Sedita, M. and Seitz, Thomas and Sgura, I. and Simeone, F. and Siotis, I. and Sipala, V. and Spisso, B. and Spurio, Maurizio and Stavropoulos, G. and Steijger, J. and Stellacci, S. M. and Stransky, Dominik and Taiuti, M. and Tayalati, Y. and Tezier, D. and Theraube, S. and Thompson, Lee and Timmer, P. and Tonnis, C. and Trasatti, L. and Trovato, Agata and Tsirigotis, A. and Tzamarias, S. and Tzamariudaki, E. and Vallage, B. and Van Elewyck, V. and Vermeulen, J. and Vicini, Piero and Viola, Salvatore and Vivolo, D. and Volkert, Marco and Voulgaris, G. and Wiggers, Leo and Wilms, Jörn and De Wolf, E. and Zachariadou, K. and Zornoza, J. D. and Zuniga, Juan},
doi = {10.1088/0954-3899/43/8/084001},
faupublication = {yes},
journal = {Journal of Physics G: Nuclear and Particle Physics},
keywords = {deep sea neutrino telescope; neutrino astronomy; neutrino mass hierarchy; neutrino physics},
peerreviewed = {unknown},
title = {{Letter} of intent for {KM3NeT} 2.0},
volume = {43},
year = {2016}
}
@inproceedings{faucris.246884248,
abstract = {In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters omega Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters.},
author = {Geier, Stephan and Ostensen, R. H. and Nemeth, Peter and Heber, Ulrich and Fusillo, Nicola Pietro Gentile and Gänsicke, Boris T. and Telting, John and Green, E. M. and Schaffenroth, Johannes},
doi = {10.1515/astro-2017-0432},
faupublication = {yes},
keywords = {stars: subdwarfs;stars: horizontal branch;catalogs},
pages = {164-168},
peerreviewed = {Yes},
publisher = {DE GRUYTER POLAND SP ZOO},
title = {{Meet} the family - the catalog of known hot subdwarf stars},
volume = {26},
year = {2017}
}
@article{faucris.246878570,
abstract = {The formation of sdBs as well as the chemical composition of their atmospheres is still puzzling. While helium and other light elements are depleted relative to solar values, heavy elements are highly enriched. Diffusion processes in the hot, radiative atmosphere of these stars are the most likely explanation. Although several attempts have been made, it has not yet been possible to model all the observed features of sdB atmospheres. A drawback of most prior studies was the small sample size. We present a detailed abundance analysis of 139 sdBs. A general trend of enrichment was found with increasing temperature for most of the heavier elements. The lighter elements like carbon, oxygen and nitrogen are depleted and less affected by temperature. Although there is considerable scatter from one star to the other, the general abundance patterns in most sdBs are similar. An interplay between gravitational settling, radiative levitation and weak winds is most likely responsible. About 3% of the analysed stars show an enrichment in carbon and helium, which cannot be explained in the framework of diffusion alone. Nuclear processed material must have been transported to the surface somehow.},
author = {Geier, Stephan and Heber, Ulrich and Heber, Ulrich and Edelmann, Heinz and Morales-Rueda, L. and Napiwotzki, R.},
doi = {10.1007/s10509-010-0326-x},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Stars: horizontal branch;Stars: abundances;Stars: chemically peculiar;Stars: atmospheres},
pages = {127-131},
peerreviewed = {Yes},
title = {{Metal} abundances of subdwarf {B} stars-the extended sample},
volume = {329},
year = {2010}
}
@article{faucris.272207602,
abstract = {We report the discovery of J0624-6948, a low-surface brightness radio ring, lying between the Galactic Plane and the large magellanic cloud (LMC). It was first detected at 888 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP), and with a diameter of similar to 196 arcsec. This source has phenomenological similarities to odd radio circles (ORCs). Significant differences to the known ORCs - a flatter radio spectral index, the lack of a prominent central galaxy as a possible host, and larger apparent size - suggest that J0624-6948 may be a different type of object. We argue that the most plausible explanation for J0624-6948 is an intergalactic supernova remnant due to a star that resided in the LMC outskirts that had undergone a single-degenerate type Ia supernova, and we are seeing its remnant expand into a rarefied, intergalactic environment. We also examine if a massive star or a white dwarf binary ejected from either galaxy could be the supernova progenitor. Finally, we consider several other hypotheses for the nature of the object, including the jets of an active galactic nucleus (30Dor) or the remnant of a nearby stellar super-flare.},
author = {Filipovic, Miroslav D. and Payne, J. L. and Alsaberi, R. Z. E. and Norris, R. P. and Macgregor, P. J. and Rudnick, Lawrence and Koribalski, B. S. and Leahy, D. and Ducci, L. and Kothes, R. and Andernach, H. and Barnes, L. and Bojicic, I. S. and Bozzetto, L. M. and Brose, R. and Collier, J. D. and Crawford, E. J. and Crocker, R. M. and Dai, S. and Galvin, T. J. and Haberl, F. and Heber, Ulrich and Hill, T. and Hopkins, A. M. and Hurley-Walker, N. and Ingallinera, A. and Jarrett, T. and Kavanagh, P. J. and Lenc, E. and Luken, K. J. and Mackey, D. and Manojlovic, P. and Maggi, P. and Maitra, C. and Pennock, C. M. and Points, S. and Riggi, S. and Rowell, G. and Safi-Harb, S. and Sano, H. and Sasaki, Manami and Shabala, S. and Stevens, J. and Van Loon, J. Th and Tothill, N. F. H. and Umana, G. and Urosevic, D. and Velovic, V. and Vernstrom, T. and West, J. L. and Wan, Z.},
doi = {10.1093/mnras/stac210},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2022-04-01},
pages = {265-284},
peerreviewed = {Yes},
title = {{Mysterious} odd radio circle near the large magellanic cloud - an intergalactic supernova remnant?},
volume = {512},
year = {2022}
}
@article{faucris.246881975,
abstract = {Several B-type main-sequence stars show chemical peculiarities. A particularly striking class are the He-3 stars, which exhibit a remarkable enrichment of He-3 with respect to He-4. This isotopic anomaly has also been found in blue horizontal branch (BHB) and subdwarf B (sdB) stars, which are helium-core burning stars of the extreme horizontal branch. Recent surveys uncovered 11 He-3 sdBs. The He-3 anomaly is not due to thermonuclear processes, but caused by atomic diffusion in the stellar atmosphere. Using a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars, we analyzed high-quality spectra of two known He-3 BHBs and nine known He-3 sdBs to determine their isotopic helium abundances and He-4/He-3 abundance ratios. We redetermined their atmospheric parameters and analyzed selected He I lines, including lambda 4922 angstrom and lambda 6678 angstrom, which are very sensitive to He-4/He-3. Most of the He-3 sdBs cluster in a narrow temperature strip between 26 000K and 30 000K and are helium deficient in accordance with previous LTE analyses. BD + 48 degrees 2721 is reclassified as a BHB star because of its low temperature (T-eff = 20 700 K). Whereas He-4 is almost absent (He-4/He-3 < 0.25) in most of the known He-3 stars, other sample stars show abundance ratios up to He-4/He-3 similar to 2.51. A search for He-3 stars among 26 candidate sdBs from the ESO SPY survey led to the discovery of two new He-3 sdB stars (HE 0929-0424 and HE 1047-0436). The observed helium line profiles of all BHBs and of three sdBs are not matched by chemically homogeneous atmospheres, but hint at vertical helium stratification. This phenomenon has been seen in other peculiar B-type stars, but is found for the first time for sdBs. We estimate helium to increase from the outer to the inner atmosphere by factors ranging from 1.4 (SB 290) up to 8.0 (BD + 48 degrees 2721).},
author = {Schneider, David and Irrgang, Andreas and Heber, Ulrich and Heber, Ulrich and Nieva, M. F. and Przybilla, N.},
doi = {10.1051/0004-6361/201833182},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: chemically peculiar;stars: atmospheres;stars: fundamental parameters;stars: abundances;subdwarfs;stars: horizontal-branch},
peerreviewed = {Yes},
title = {{NLTE} spectroscopic analysis of the {He}-3 anomaly in subluminous {B}-type stars},
volume = {618},
year = {2018}
}
@inproceedings{faucris.247101154,
abstract = {Some young, massive stars can be found in the Galactic halo. As star formation is unlikely to occur in the halo, they must have been formed in the disk and been ejected shortly afterwards. One explanation is a supernova in a tight binary system. The companion is ejected and becomes a runaway star. HD271791 is the kinematically most extreme runaway star known (Galactic restframe velocity 725±195km s-1, which is even larger than the Galactic escape velocity). Moreover, an analysis of the optical spectrum showed an enhancement of the α-process elements. This indicates the capture of supernova ejecta, and therefore an origin in a core-collapse supernova. As such high space velocities are not reached by the runaway stars in classical binary supernova ejection scenarios, a very massive but compact primary, probably of Wolf-Rayet type is required. HD271791 is therefore a perfect candidate for studying nucleosynthesis in a supernova of probably type Ibc. The goal of this project is to determine the abundances of a large number of elements from the α-process, the iron group, and heavier elements by a quantitative analysis of the optical and UV spectral range. Detailed line-formation calculations are employed that account for deviations from local thermodynamic equilibrium (non-LTE). We intend to verify whether corecollapse supernova are a site of r-process element production. Here, we state the current status of the project.},
author = {Schaffenroth, Veronika and Przybilla, Norbert and Butler, Keith and Irrgang, Andreas and Heber, Ulrich},
booktitle = {Proceedings of Science},
date = {2014-07-07/2014-07-11},
editor = {Zoltan Elekes, Zsolt Fulop},
faupublication = {yes},
note = {CRIS-Team Scopus Importer:2020-12-21},
peerreviewed = {unknown},
publisher = {Proceedings of Science (PoS)},
title = {{Observations} of the extreme runaway {HD271791}: {Nucleosynthesis} in a core-collapse supernova},
venue = {Debrecen},
volume = {07-11-July-2015},
year = {2014}
}
@article{faucris.317553642,
abstract = {Blue large-amplitude pulsators (BLAPs) make up a rare class of hot pulsating stars with effective temperatures of ≈30 000 K and surface gravities of 4.0–5.0 dex (cgs). The evolutionary origin and current status of BLAPs is not well understood, largely based on a lack of spectroscopic observations and no available mass constraints. However, several theoretical models have been proposed that reproduce their observed properties, including studies that identify them as pulsating helium-core pre-white dwarfs (He-core pre-WDs). We present here follow-up high-speed photometry and phase-resolved spectroscopy of one of the original 14 BLAPs, OGLE-BLAP-009, discovered during the Optical Gravitational Lensing Experiment. We aim to explore its pulsation characteristics and determine stellar properties such as mass and radius in order to test the consistency of these results with He-core pre-WD models. Using the mean atmospheric parameters found using spectroscopy, we fit a spectral energy distribution to obtain a preliminary estimate of the radius, luminosity, and mass by making use of the Gaia parallax. We then compare the consistency of these results to He-core pre-WD models generated using Modules for Experiments in Stellar Astrophysics, with predicted pulsation periods implemented using GYRE. We find that our mass constraints are in agreement with a low-mass He-core pre-WD of ≈0.30 M◦},
author = {Bradshaw, Corey W. and Dorsch, Matti and Kupfer, Thomas and Barlow, Brad N. and Heber, Ulrich and Bauer, Evan B. and Bildsten, Lars and van Roestel, Jan},
doi = {10.1093/mnras/stad3845},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {asteroseismology; stars: evolution; stars: individual: OGLE-BLAP-009; stars: oscillations (including pulsations)},
note = {CRIS-Team Scopus Importer:2024-02-02},
pages = {10239-10253},
peerreviewed = {Yes},
title = {{OGLE}-{BLAP}-009 – a case study for the properties and evolution of blue large-amplitude pulsators},
volume = {527},
year = {2024}
}
@inproceedings{faucris.246884509,
abstract = {Decades ago, He-3 isotope enrichment in helium-weak B-type main-sequence, in blue horizontal branch and in hot subdwarf B (sdB) stars, i.e., helium-core burning stars of the extreme horizontal branch, were discovered. Diffusion processes in the atmosphere of these stars lead to the observed abundance anomalies. Quantitative spectral analyses of high-resolution spectra to derive photospheric isotopic helium abundance ratios for known He-3 sdBs have not been performed yet. We present preliminary results of high-resolution and high S/N spectra to determine the He-3 and He-4 abundances of nine known He-3 sdBs. We used a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars investigating multiple He I lines, including lambda 4922 angstrom and lambda 6678 angstrom, which show the strongest isotopic shifts in the optical spectral range. We also report the discovery of four new He-3 sdBs from the ESO Supernova Progenitor survey. Most of the He-3 sdBs cluster in a narrow temperature strip between similar to 26000 K and similar to 30000 K and have almost no atmospheric He-4 at all. Interestingly, three He-3 sdBs show evidence for vertical helium stratification.},
author = {Schneider, David and Irrgang, Andreas and Heber, Ulrich and Nieva, M. F. and Przybilla, Norbert},
doi = {10.1515/astro-2017-0430},
faupublication = {yes},
keywords = {Stars: chemically peculiar;Stars: atmospheres;Stars: fundamental parameters;Stars: abundances;subdwarfs;Stars: horizontal-branch},
pages = {139-151},
peerreviewed = {Yes},
publisher = {SCIENDO},
title = {{On} the {He}-3 anomaly in hot subdwarf {B} stars},
volume = {26},
year = {2017}
}
@article{faucris.229927584,
abstract = {We report the discovery of three stars that, along with the prototype LP 40-365, form a distinct class of chemically peculiar runaway stars that are the survivors of thermonuclear explosions. Spectroscopy of the four confirmed LP 40-365 stars finds ONe-dominated atmospheres enriched with remarkably similar amounts of nuclear ashes of partial O- and Si-burning. Kinematic evidence is consistent with ejection from a binary supernova progenitor; at least two stars have rest-frame velocities indicating they are unbound to the Galaxy. With masses and radii ranging between 0.20 and 0.28Mθ and between 0.16 and 0.60 Rθ, respectively, we speculate these inflated white dwarfs are the partly burnt remnants of either peculiar Type Iax or electron-capture supernovae. Adopting supernova rates from the literature, we estimate that ∼20 LP 40-365 stars brighter than 19 mag should be detectable within 2 kpc from the Sun at the end of the Gaia mission. We suggest that as they cool, these stars will evolve in their spectroscopic appearance, and eventually become peculiar O-rich white dwarfs. Finally, we stress that the discovery of new LP 40-365 stars will be useful to further constrain their evolution, supplying key boundary conditions to the modelling of explosion mechanisms, supernova rates, and nucleosynthetic yields of peculiar thermonuclear explosions.},
author = {Raddi, Roberto and Hollands, M. A. and Koester, D. and Hermes, J. J. and Gansicke, B. T. and Heber, Ulrich and Shen, K. J. and Townsley, D. M. and Pala, A. F. and Reding, J. S. and Toloza, O. F. and Pelisoli, I. and Geier, S. and Fusillo, N. P. Gentile and Munari, U. and Strader, J.},
doi = {10.1093/mnras/stz1618},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {Galaxy: Kinematics and dynamics; Stars: Individual: LP 40-365; Subdwarfs; Supernovae: General-white dwarfs},
note = {CRIS-Team Scopus Importer:2019-11-29},
pages = {1489-1508},
peerreviewed = {Yes},
title = {{Partly} burnt runaway stellar remnants from peculiar thermonuclear supernovae},
volume = {489},
year = {2019}
}
@article{faucris.246881127,
abstract = {Hypervelocity stars are rare objects, mostly main-sequence (MS) B stars, traveling so fast that they will eventually escape from the Milky Way. Recently, it has been shown that the popular Hills mechanism, in which a binary system is disrupted via a close encounter with the supermassive black hole at the Galactic center, may not be their only ejection mechanism. The analyses of Gaia data ruled out a Galactic center origin for some of them, and instead indicated that they are extreme disk runaway stars ejected at velocities exceeding the predicted limits of classical scenarios (dynamical ejection from star clusters or binary supernova ejection). We present the discovery of a new extreme disk runaway star, PG 1610+062, which is a slowly pulsating B star bright enough to be studied in detail. A quantitative analysis of spectra taken with ESI at the Keck Observatory revealed that PG 1610+062 is a late B-type MS star of 4-5 M-circle dot with low projected rotational velocity. Abundances (C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe) were derived differentially with respect to the normal B star HD 137366 and indicate that PG 1610+062 is somewhat metal rich. A kinematic analysis, based on our spectrophotometric distance (17.3 kpc) and on proper motions from Gaia's second data release, shows that PG 1610+062 was probably ejected from the Carina-Sagittarius spiral arm at a velocity of 550 +/- 40 km s(-1), which is beyond the classical limits. Accordingly, the star is in the top five of the most extreme MS disk runaway stars and is only the second among the five for which the chemical composition is known.},
author = {Irrgang, Andreas and Geier, Stephan and Heber, Ulrich and Kupfer, Thomas and Furst, F. S.},
doi = {10.1051/0004-6361/201935429},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;stars: individual: HD 137366;stars: kinematics and dynamics;stars: individual: PG 1610+062;stars: early-type},
peerreviewed = {Yes},
title = {{PG} 1610+062: a runaway {B} star challenging classical ejection mechanisms},
volume = {628},
year = {2019}
}
@article{faucris.246887495,
abstract = {PSR J1024-0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to a reexamination of its properties. We present updated radio timing observations along with new and archival optical data which show that PSR J1024-0719 is most likely in a long-period (2-20 kyr) binary system with a low-mass (approximate to 0.4 M-circle dot), low-metallicity (Z approximate to -0.9 dex) main-sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, which is consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters.},
author = {Kaplan, D. L. and Kupfer, Thomas and Nice, David J. and Irrgang, Andreas and Heber, Ulrich and Arzoumanian, Zaven and Beklen, Elif and Crowter, Kathryn and Decesar, Megan E. and Demorest, Paul B. and Dolch, Timothy and Ellis, Justin A. and Ferdman, Robert D. and Ferrara, Elizabeth C. and Fonseca, Emmanuel and Gentile, Peter A. and Jones, Glenn and Jones, Megan L. and Kreuzer, Simon and Lam, Michael T. and Levin, Lina and Lorimer, Duncan R. and Lynch, Ryan S. and McLaughlin, Maura A. and Miller, Adam A. and Ng, Cherry and Pennucci, Timothy T. and Prince, Tom A. and Ransom, Scott M. and Ray, Paul S. and Spiewak, Renee and Stairs, Ingrid H. and Stovall, Kevin and Swiggum, Joseph and Zhu, Weiwei},
doi = {10.3847/0004-637X/826/1/86},
faupublication = {yes},
journal = {Astrophysical Journal},
keywords = {binaries: general;pulsars: individual (PSR J1024-0719);stars: distances},
peerreviewed = {Yes},
title = {{PSR} {J1024}-0719: {A} {MILLISECOND} {PULSAR} {IN} {AN} {UNUSUAL} {LONG}-{PERIOD} {ORBIT}},
volume = {826},
year = {2016}
}
@article{faucris.246884770,
abstract = {We present the discovery of the hot subdwarf B star (sdB) binary PTF1 J082340.04+081936.5. The system has an orbital period of P-orb = 87.49668(1) minutes (0.060761584(10) days), making it the second-most compact sdB binary known. The light. curve shows ellipsoidal variations. Under the assumption that the sdB primary is synchronized with the orbit, we find a mass of = M-sdB =0.45(-0.07)(+0.009) M-circle dot, a companion white dwarf mass of M-WD = 0.46(-0.09)(+0.12)M(circle dot), and a mass ratio of q =M-WD/M(sdB)1.03+(+0.10)(0.08). The future evolution was calculated using the MESA stellar evolution code. Adopting a canonical sdB mass of M-sdB = 0.47 M-circle dot, we find that the sdB still burns helium at the time it will fill its Roche lobe if the orbital period was less than 106 minutes at the exit from the last common envelope (CE) phase. For longer CE exit periods, the sdB will have stopped burning helium and turned into a C/O white dwarf at the time of contact. Comparing the spectroscopically derived log g and T-eff with our MESA models, we find that an sdB model with a hydrogen envelope mass of 5 x 10(-4) M-circle dot matches the measurements at a post-CE age of 94 Myr, corresponding to a post-CE orbital period of 109 minutes, which is close to the limit to start accretion while the sdB is still burning helium.},
author = {Kupfer, Thomas and van Roestel, Jan and Brooks, Jared and Geier, Stephan and Marsh, Tom R. and Groot, Paul J. and Bloemen, Steven and Prince, Thomas A and Bellm, Eric and Heber, Ulrich and Bildsten, Lars and Miller, Adam A. and Dyer, Martin J. and Dhillon, Vik S. and Green, Matthew and Irawati, Puji and Laher, Russ R and Littlefair, Stuart P. and Shupe, David L and Steidel, Charles C. and Rattansoon, Somsawat and Pettini, Max},
doi = {10.3847/1538-4357/835/2/131},
faupublication = {yes},
journal = {Astrophysical Journal},
keywords = {binaries: close;stars: individual (PTF1 J082340.04+081936.5);subdwarfs;white dwarfs},
peerreviewed = {Yes},
title = {{PTF1} {J082340}.04+081936.5: {A} {Hot} {Subdwarf} {B} {Star} with a {Low}-mass {White} {Dwarf} {Companion} in an 87-minute {Orbit}},
volume = {835},
year = {2017}
}
@article{faucris.246882242,
abstract = {Context. Hypervelocity stars (HVSs) travel so fast that they may leave the Galaxy. The tidal disruption of a binary system by the supermassive black hole in the Galactic center is widely assumed to be their ejection mechanism.Aims. To test the hypothesis of an origin in the Galactic center using kinematic investigations, the current space velocities of the HVSs need to be determined. With the advent of Gaia's second data release, accurate radial velocities from spectroscopy are complemented by proper motion measurements of unprecedented quality. Based on a new spectroscopic analysis method, we provide revised distances and stellar ages, both of which are crucial to unravel the nature of the HVSs.Methods. We reanalyzed low-resolution optical spectra of 14 HVSs from the MMT HVS survey using a new grid of synthetic spectra, which account for deviations from local thermodynamic equilibrium, to derive effective temperatures, surface gravities, radial velocities, and projected rotational velocities. Stellar masses, radii, and ages were then determined by comparison with stellar evolutionary models that account for rotation. Finally, these results were combined with photometric measurements to obtain spectroscopic distances.Results. The resulting atmospheric parameters are consistent with those of main sequence stars with masses in the range 2.5-5.0 M-circle dot. The majority of the stars rotate at fast speeds, providing further evidence for their main sequence nature. Stellar ages range from 90 to 400 Myr and distances (with typical 1 sigma-uncertainties of about 10-15%) from 30 to 100 kpc. Except for one object (B 711), which we reclassify as A-type star, all stars are of spectral type B.Conclusions. The spectroscopic distances and stellar ages derived here are key ingredients for upcoming kinematic studies of HVSs based on Gaia proper motions.},
author = {Irrgang, Andreas and Kreuzer, Simon and Heber, Ulrich and Brown, W.},
doi = {10.1051/0004-6361/201833315},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: distances;stars: early-type;stars: fundamental parameters},
peerreviewed = {Yes},
title = {quantitative spectral analysis of 14 hypervelocity stars from the {MMT} survey},
volume = {615},
year = {2018}
}
@article{faucris.246887763,
abstract = {Context. HD 188112 is a bright (V = 10 : 2 mag) hot subdwarf B (sdB) star with a mass too low to ignite core helium burning and is therefore considered a pre-extremely low-mass (ELM) white dwarf (WD). ELM WDs (M less than or similar to 0.3 M-circle dot) are He-core objects produced by the evolution of compact binary systems.Aims. We present in this paper a detailed abundance analysis of HD188112 based on high-resolution Hubble Space Telescope (HST) near-and far-ultraviolet spectroscopy. We also constrain the mass of the star's companion.Methods. We use hybrid non-LTE model atmospheres to fit the observed spectral lines, and to derive the abundances of more than a dozen elements and the rotational broadening of metallic lines.Results. We confirm the previous binary system parameters by combining radial velocities measured in our UV spectra with the previously published values. The system has a period of 0.60658584 days and a WD companion with M >= 0.70 M-circle dot. By assuming a tidally locked rotation combined with the projected rotational velocity (v sin i = 7.9 +/- 0.3 km s(-1)), we constrain the companion mass to be between 0.9 and 1.3 M-circle dot. We further discuss the future evolution of the system as a potential progenitor of an underluminous type Ia supernova. We measure abundances for Mg, Al, Si, P, S, Ca, Ti, Cr, Mn, Fe, Ni, and Zn, and for the trans-iron elements Ga, Sn, and Pb. In addition, we derive upper limits for the C, N, O elements and find HD188112 to be strongly depleted in carbon. We find evidence of non-LTE e ff ects on the line strength of some ionic species such as Si II and Ni II. The metallic abundances indicate that the star is metal-poor, with an abundance pattern most likely produced by diffusion effects.},
author = {Latour, Marilyn and Heber, Ulrich and Irrgang, Andreas and Schaffenroth, Veronika and Geier, Stephan and Hillebrandt, W. and Roepke, F. K. and Taubenberger, S. and Kromer, Markus and Fink, M.},
doi = {10.1051/0004-6361/201527445},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: abundances;stars: atmospheres;stars: individual: HD 188112;subdwarfs;white dwarfs;binaries: general},
month = {Jan},
peerreviewed = {Yes},
title = {{Quantitative} spectral analysis of the {sdB} star {HD188112}: {A} helium-core white dwarf progenitor},
volume = {585},
year = {2016}
}
@article{faucris.246885039,
abstract = {Extreme helium stars (EHe stars) are hydrogen-deficient supergiants of spectral type A and B. They are believed to result from mergers in double degenerate systems. In this paper, we present a detailed quantitative non-LTE spectral analysis for BD+10. 2179, a prototype of this rare class of stars, using UV-Visual Echelle Spectrograph and Fiber-fed Extended Range Optical Spectrograph spectra covering the range from similar to 3100 to 10 000 angstrom. Atmosphere model computations were improved in two ways. First, since the UV metal line blanketing has a strong impact on the temperature-density stratification, we used the ATLAS12 code. Additionally, We tested ATLAS12 against the benchmark code STERNE3, and found only small differences in the temperature and density stratifications, and good agreement with the spectral energy distributions. Secondly, 12 chemical species were treated in non-LTE. Pronounced nonLTE effects occur in individual spectral lines but, for the majority, the effects are moderate to small. The spectroscopic parameters give T-eff = 17 300 +/- 300 K and log g = 2.80 +/- 0.10, and an evolutionary mass of 0.55 +/- 0.05 M circle dot. The star is thus slightly hotter, more compact and less massive than found in previous studies. The kinematic properties imply a thick-disc membership, which is consistent with the metallicity [Fe/H] approximate to -1 and alpha-enhancement. The refined light-element abundances are consistent with the white dwarf merger scenario. We further discuss the observed helium spectrum in an appendix, detecting dipole-allowed transitions from about 150 multiplets plus the most comprehensive set of known/predicted isolated forbidden components to date. Moreover, a so far unreported series of pronounced forbidden He I components is detected in the optical-UV.},
author = {Kupfer, Thomas and Przybilla, N. and Heber, Ulrich and Heber, Ulrich and Jeffery, C. S. and Behara, N. T. and Butler, K.},
doi = {10.1093/mnras/stx1541},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {line: formation;stars: abundances;stars: atmospheres;stars: fundamental parameters;stars: individual: BD+10 degrees 2179},
pages = {877-890},
peerreviewed = {Yes},
title = {{Quantitative} spectroscopy of extreme helium stars {Model} atmospheres and a non-{LTE} abundance analysis of {BD}+10 degrees 2179},
volume = {471},
year = {2017}
}
@article{faucris.246890005,
author = {Copperwheat, C. M. and Morales-Rueda, L. and Marsh, Thomas R. and Maxted, P. F. L. and Heber, Ulrich},
doi = {10.1093/mnras/stv1248},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {errata;addenda;binaries: close;binaries: spectroscopic;subdwarfs},
pages = {4412-4412},
peerreviewed = {Yes},
title = {{Radial} velocity measurements of {Subdwarf} {B} stars (vol 415, pg 1381, 2011)},
volume = {451},
year = {2015}
}
@article{faucris.276353609,
abstract = {Hot subdwarf stars represent a late and peculiar stage in the evolution of low-mass stars, since they are likely formed by close binary interactions. In this work, we perform a radial velocity (RV) variability study of a sample of 646 hot subdwarfs with multi-epoch radial velocities based on spectra from Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST). The atmospheric parameters and RVs were taken from the literature. For stars with archival spectra but without literature values, we determined the parameters by fitting model atmospheres. In addition, we redetermined the atmospheric parameters and RVs for all the He-enriched sdO/Bs. This broad sample allowed us to study RV-variability as a function of the location in the T-eff - log g- and T-eff - log n(He)/n(H) diagrams in a statistically significant way. We used the fraction of RV-variable stars and the distribution of the maximum RV variations Delta RVmax as diagnostics. Both indicators turned out to be quite inhomogeneous across the studied parameter ranges. A striking feature is the completely dissimilar behaviour of He-poor and He-rich hot subdwarfs. While the former have a high fraction of close binaries, almost no significant RV variations could be detected for the latter. This has led us to the conclusion that there is likely no evolutionary connection between these subtypes. On the other hand, intermediate He-rich- and extreme He-rich sdOB/Os are more likely to be related. Furthermore, we conclude that the vast majority of this population is formed via one or several binary merger channels. Hot subdwarfs with temperatures cooler than similar to 24 000 K tend to show fewer and smaller RV-variations. These objects might constitute a new subpopulation of binaries with longer periods and late-type or compact companions. The RV-variability properties of the extreme horizontal branch (EHB) and corresponding post-EHB populations of the He-poor hot subdwarfs match and confirm the predicted evolutionary connection between them. Stars found below the canonical EHB at somewhat higher surface gravities show large RV variations and a high RV variability fraction. These properties are consistent with most of them being low-mass EHB stars or progenitors of low-mass helium white dwarfs in close binaries.},
author = {Geier, S. and Dorsch, Matti and Pelisoli, I. and Reindl, N. and Heber, Ulrich and Irrgang, Andreas},
doi = {10.1051/0004-6361/202143022},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
note = {CRIS-Team WoS Importer:2022-06-03},
peerreviewed = {Yes},
title = {{Radial} velocity variability and the evolution of hot subdwarf stars},
volume = {661},
year = {2022}
}
@article{faucris.246888030,
abstract = {In the course of the MUCHFUSS project we recently discovered four radial velocity (RV) variable, hot (T-eff approximate to 80 000-110 000 K) post-asymptotic giant branch (AGB) stars. Among them, we found the first known RV variable O(He) star, the only second known RV variable PG1159 close binary candidate, as well as the first two naked (i.e., without planetary nebula (PN)) H-rich post-AGB stars of spectral type O(H) that show significant RV variations. We present a non-LTE spectral analysis of these stars along with one further O(H)-type star whose RV variations were found to be not significant. We also report the discovery of a far-infrared excess in the case of the PG1159 star. None of the stars in our sample displays nebular emission lines, which can be explained well in terms of a very late thermal pulse evolution in the case of the PG1159 star. The "missing" PNe around the O(H)-type stars seems strange, since we find that several central stars of PNe have much longer post-AGB times. Besides the non-ejection of a PN, the occurrence of a late thermal pulse, or the re-accretion of the PN in the previous post-AGB evolution offer possible explanations for those stars not harbouring a PN (anymore). In the case of the O(He) star J0757, we speculate that it might have been previously part of a compact He transferring binary system. In this scenario, the mass transfer must have stopped after a certain time, leaving behind a low-mass close companion that may be responsible for the extreme RV shift of 107.0 +/- 22.0 km s(-1) that was measured within only 31min.},
author = {Reindl, N. and Geier, Stephan and Kupfer, Thomas and Bloemen, S. and Schaffenroth, Veronika and Heber, Ulrich and Barlow, Brad N. and Ostensen, R. H.},
doi = {10.1051/0004-6361/201527637},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {binaries: spectroscopic;stars: AGB and post-AGB;stars: evolution;stars: atmospheres},
peerreviewed = {Yes},
title = {{Radial} velocity variable, hot post-{AGB} stars from the {MUCHFUSS} project {Classification}, atmospheric parameters, formation scenarios},
volume = {587},
year = {2016}
}
@article{faucris.246892131,
abstract = {Context. Hyper-velocity stars (HVS) are moving so fast that they are unbound to the Galaxy. Dynamical ejection by a supermassive black hole is favoured to explain their origin.Aims. Locating the place of birth of an individual HVS is of utmost importance to understanding the ejection mechanism.Methods. SDSS J013655.91+242546.0 (J0136+2425 for short) was found amongst three high-velocity stars (drawn from a sample of more than 10 000 blue stars), for which proper motions were measured. A kinematical as well as a quantitative NLTE spectral analysis was performed. When combined with the radial velocity (RV) and the spectroscopic distance, the trajectory of the star in the Galactic potential was reconstructed.Results. J0136+2425 is found to be an A-type main-sequence star travelling at approximate to 590 km s(-1), possibly unbound to the Galaxy and originating in the outer Galactic rim nowhere near the Galactic centre.Conclusions. J0136+2425 is the second HVS candidate with measured proper motion, besides the massive B star HD 271791, and also the second for which its proper motion excludes a Galactic centre origin and, hence, the SMBH slingshot mechanism. Most known HVS are late B-type stars of about 3 M(circle dot). With a mass of 2.45 M(circle dot), J0136+2425 resembles a typical HVS far more than HD 271791 does. Hence, this is the first time that a typical HVS is found not to originate in the Galactic centre. Its ejection velocity from the disk is so high (550 km s(-1)) that the extreme supernova binary scenario proposed for HD 271791 is very unlikely.},
author = {Tillich, A. and Przybilla, N. and Scholz, R. -D. and Heber, Ulrich and Heber, Ulrich},
doi = {10.1051/0004-6361/200913173},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: kinematics;stars: individual: SDSSJ013655.91+242546.0;stars: atmospheres;line profiles},
pages = {L37-L40},
peerreviewed = {Yes},
title = {{SDSS} {J013655}.91+242546.0-an {A}-type hyper-velocity star from the outskirts of the {Galaxy}},
volume = {507},
year = {2009}
}
@article{faucris.310762797,
abstract = {Aims. We want to study the population of blue horizontal branch (HB) stars in the centres of globular clusters (GC) for the first time by exploiting the unique combination of MUSE spectroscopy and HST photometry. In this work, we characterize their properties in the GCs ω Cen and NGC 6752. Methods. We use dedicated model atmospheres and grids of synthetic spectra computed using a hybrid LTE/NLTE modeling approach to fit the MUSE spectra of HB stars hotter than 8000 K in both clusters. The spectral fits provide estimates of the effective temperature (Teff), surface gravity (log É¡), and helium abundance of the stars. The model grids are further used to fit the HST magnitudes of the stars, that is, their spectral energy distributions (SEDs). From the SED fits, we derive the average reddening, radius, luminosity, and mass of the stars in our sample. Results. The atmospheric and stellar properties that we derive for the stars in our sample are in good agreement with theoretical expectations. In particular, the stars cooler than ~15 000 K closely follow the theoretical predictions on radius, log É¡, and luminosity for helium-normal (Y = 0.25) models. In ω Cen, we show that the majority of these cooler HB stars cannot originate from a helium-enriched population with Y > 0.35. The properties of the hotter stars (radii and luminosities) are still in reasonable agreement with theoretical expectations, but the individual measurements show a large scatter. For these hot stars, we find a mismatch between the effective temperatures indicated from the MUSE spectral fits and the photometric fits, with the latter returning Teff lower by ~3000 K. We use three different diagnostics, namely the position of the G-jump and changes in metallicity and helium abundances, to place the onset of diffusion in the stellar atmospheres at Teff between 11 000 and 11 500 K. Our sample includes two stars known as photometric variables; we confirm one to be a bona fide extreme HB object but the other is a blue straggler star. Finally, unlike what has been reported in the literature, we do not find significant differences between the properties (e.g., log É¡, radius, and luminosity) of the stars in the two clusters. Conclusions. We show that our analysis method - combining MUSE spectra and HST photometry of HB stars in GCs - is a powerful tool for characterising their stellar properties. With the availability of MUSE and HST observations of additional GCs, we have a unique opportunity to combine homogeneous spectroscopic and photometric data to study and compare the properties of blue HB stars in different GCs. },
author = {Latour, M. and Hämmerich, Steven and Dorsch, Matti and Heber, Ulrich and Husser, T. O. and Kamman, S. and Dreizler, S. and Brinchmann, J.},
doi = {10.1051/0004-6361/202346597},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Globular clusters: individual: NGC 5139; Globular clusters: individual: NGC 6752; Stars: fundamental parameters; Stars: horizontal-branch},
note = {CRIS-Team Scopus Importer:2023-09-22},
peerreviewed = {Yes},
title = {{SHOTGLAS}: {II}. {MUSE} spectroscopy of blue horizontal branch stars in the core of ω {Centauri} and {NGC6752}},
volume = {677},
year = {2023}
}
@article{faucris.265347708,
abstract = {We present an overview of eclipsing systems of the HW-Virginis (HW-Vir) type, based on space observations from the Transiting Exoplanet Survey Satellite (TESS) mission. We perform a detailed analysis of the properties of AA Doradus (AA Dor), which was monitored for almost a full year. This excellent time series data set permitted us to search for both stellar pulsations and eclipse timing variations. In addition, we used the high-precision trigonometric parallax from Gaia Early Data Release 3 to make an independent determination of the fundamental stellar parameters. No convincing pulsations were detected down to a limit of 76 parts per million; however, we detected one peak with false alarm probability of 0.2 per cent. 20 s cadences being collected during Year 3 should confirm or reject our detection. From eclipse timing measurements we were able to confirm that the orbital period is stable, with an upper limit to any period change of 5.75 × 10−13 s s−1. The apparent offset of the secondary eclipse is consistent with the predicted Rømer delay when the primary mass is that of a canonical extended horizontal branch star. Using parallax and a spectral energy distribution corroborates that the mass of the primary in AA Dor is canonical, and its radius and luminosity are consistent with an evolutionary state beyond core helium burning. The mass of the secondary is found to be at the limit of hydrogen burning.},
author = {Baran, A. S. and Ostensen, R. H. and Heber, Ulrich and Irrgang, Andreas and Sanjayan, Sachu and Telting, J. H. and Reed, M. D. and Ostrowski, J.},
doi = {10.1093/mnras/stab620},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {Binaries: eclipsing; Binaries: general; Stars: individual: AA Dor; Stars: oscillations; Subdwarfs},
note = {CRIS-Team Scopus Importer:2021-10-22},
pages = {2157-2167},
peerreviewed = {Yes},
title = {{Space} observations of {AA} {Doradus} provide consistent mass determinations. {New} {HW}-{Vir} systems observed with {TESS}},
volume = {503},
year = {2021}
}
@inproceedings{faucris.246882509,
abstract = {The bright sdO star HD127493 is known to be of mixed H/He composition and excellent archival spectra covering both optical and ultraviolet ranges are available. UV spectra play a key role as they give access to many chemical species that do not show spectral lines in the optical, such as iron and nickel. This encouraged the quantitative spectral analysis of this prototypical mixed H/He composition sdO star.We determined atmospheric parameters for HD127493 in addition to the abundance of C, N, O, Si, S, Fe, and Ni in the atmosphere using non-LTE model atmospheres calculated with TLUSTY/SYNSPEC. A comparison between the parallax distance measured by Hipparcos and the derived spectroscopic distance indicate that the derived atmospheric parameters are realistic. From our metal abundance analysis, we find a strong CNO signature and enrichment in iron and nickel.},
author = {Dorsch, Matti and Latour, Marilyn and Heber, Ulrich},
doi = {10.1515/astro-2018-0007},
faupublication = {yes},
keywords = {HD127493;hot subdwarf;atmospheric abundances},
pages = {19-26},
peerreviewed = {unknown},
publisher = {DE GRUYTER POLAND SP ZOO},
title = {{Spectral} analysis of the {He}-enriched {sdO}-star {HD} 127493},
volume = {27},
year = {2018}
}
@inproceedings{faucris.246882770,
abstract = {Photometric surveys at optical, ultraviolet, and infrared wavelengths provide ever-growing datasets as major surveys proceed. Colour-colour diagrams are useful tools to identify classes of star and provide large samples. However, combining all photometric measurements of a star into a spectral energy distribution will allow quantitative analyses to be carried out. We demonstrate how to construct and exploit spectral energy distributions and colours for sublumious B (sdB) stars. The aim is to identify cool companions to hot subdwarfs and to determine atmospheric parameters of apparently single sdB stars as well as composite spectrum sdB binaries. We analyse two sdB stars with high-quality photometric data which serve as our benchmarks, the apparently single sdB HD205805 and the sdB + K5 binary PG 0749+658, briefly present preliminary results for the sample of 142 sdB binaries with known orbits, and discuss future prospects from ongoing all-sky optical space-(Gaia) and ground-based (e.g. SkyMapper) as well as NIR surveys.},
author = {Heber, Ulrich and Irrgang, Andreas and Schaffenroth, Johannes},
doi = {10.1515/astro-2018-0008},
faupublication = {yes},
keywords = {stars: early type;subdwarfs;Techniques: potometric},
pages = {35-43},
peerreviewed = {unknown},
publisher = {DE GRUYTER POLAND SP ZOO},
title = {{Spectral} energy distributions and colours of hot subluminous stars},
volume = {27},
year = {2018}
}
@inproceedings{faucris.246883031,
abstract = {HW Vir systems are rare eclipsing binary systems including a subdwarf B star (sdB) with a faint companion, mostly M-dwarfs. Up to now, 19 HW Vir systems have been published, three of them with substellar companions. We report the spectroscopic as well as photometric observation of the eclipsing sdB binary PTF1 J011339.09+225739.1 (PTF1 J0113) in a close (a=0.722 +/- 0.023 R-circle dot), short period (P = 0.0933731(3)d) orbit. A quantitative spectral analysis of the sdB yields T-eff =29280 +/- 720 K, log(g)=5.77 +/- 0.09 dex, and log(y)=-2.32 +/- 0.12. The circular orbital velocity of the sdB of K-1 =74.2 +/- 1.7 km s(-1) is derived from the radial velocity curve. Except for the strong reflection effect, no other light contribution of the companion could be detected. The light curves - recorded with ULTRACAM - were analyzed using the Wilson-Devinney code. We find an inclination angle of i=79.88 +/- 0.18 degrees. Because our first attempts to determine q failed, we calculated large grids of synthetic lightcurves for several mass ratios. Because of degeneracy, good solutions for different mass ratios were found - the one at q = 0.24 is consistent with the sdB's canonical mass (M-sdB = 0.47 M-circle dot). Accordingly, the mass of the companion is M-2=0.112 +/- 0.003 M-circle dot. The radii of the two components were also derived: R-sdB=0.178 +/- 0.006 R-circle dot and R-2 = 0.158 +/- 0.009 R-circle dot. Thus, the results for the secondary are consistent with an M-dwarf as secondary.},
author = {Woltz, Maximilian and Kupfer, Thomas and Drechsel, Horst and Heber, Ulrich and Irrgang, Andreas and Hermes, J. J. and Bloemen, Steven and Levitan, D. and Dhillon, Vik S. and Marsh, Thomas},
doi = {10.1515/astro-2018-0011},
faupublication = {yes},
keywords = {subdwarfs;binaries: eclipsing;stars: early-type;stars: evolution;stars: fundamental parameters;stars: horizontal-branch},
pages = {80-90},
peerreviewed = {unknown},
publisher = {DE GRUYTER POLAND SP ZOO},
title = {{Spectroscopic} and photometric analysis of the {HW} {Vir} star {PTF1} {J011339}.09+225739.1},
volume = {27},
year = {2018}
}
@article{faucris.246885309,
abstract = {Important tracers for the dark matter halo of the Galaxy are hypervelocity stars (HVSs), which are faster than the local escape velocity of the Galaxy and their slower counterparts, the high-velocity stars in the Galactic halo. Such HVSs are believed to be ejected from the Galactic centre (GC) through tidal disruption of a binary by the super-massive black hole (Hills mechanism). The Hyper-MUCHFUSS survey aims at finding high-velocity potentially unbound hot subdwarf stars. We present the spectroscopic and kinematical analyses of a He-sdO as well as three candidates among the sdB stars using optical Keck/ESI and VLT (X-shooter, FORS) spectroscopy. Proper motions are determined by combining positions from early-epoch photographic plates with those derived from modern digital sky surveys. The Galactic rest frame velocities range from 203 km s(-1) to 660 km s(-1), indicating that most likely all four stars are gravitationally bound to the Galaxy. With T-eff = 47 000 K and a surface gravity of log g = 5 : 7, SDSS J205030.39-061957.8 (J2050) is a spectroscopic twin of the hypervelocity He-sdO US 708. As for the latter, the GC is excluded as a place of origin based on the kinematic analysis. Hence, the Hills mechanism can be excluded for J2050. The ejection velocity is much more moderate (385 +/- 79 km s(-1)) than that of US 708 (998 +/- 68 km s(-1)). The binary thermonuclear supernova scenario suggested for US 708 would explain the observed properties of J2050 very well without pushing the model parameters to their extreme limits, as required for US 708. Accordingly, the star would be the surviving donor of a type Ia supernova. Three sdB stars also showed extreme kinematics; one could be a HVS ejected from the GC, whereas the other two could be ejected from the Galactic disk through the binary supernova mechanism. Alternatively, they might be extreme halo stars.},
author = {Ziegerer, Eva and Heber, Ulrich and Geier, Stephan and Irrgang, Andreas and Kupfer, Thomas and Fuerst, F. and Schaffenroth, Johannes},
doi = {10.1051/0004-6361/201730437},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {stars: kinematics and dynamics;subdwarfs;stars: atmospheres;Galaxy: halo},
peerreviewed = {Yes},
title = {{Spectroscopic} twin to the hypervelocity {sdO} star {US} 708 and three fast {sdB} stars from the {Hyper}-{MUCHFUSS} project},
volume = {601},
year = {2017}
}
@inproceedings{faucris.246883292,
abstract = {We present a status report of our spectroscopic analysis of subdwarf binaries consisting of a subdwarf and a F/G/K-type main-sequence companion. These systems selected from SDSS photometry show significant excess in the (infra-)red which can not be explained by interstellar reddening. Inspection of SDSS spectra revealed that most of them are composite spectrum sdB binaries. Once their spectra are disentangled, a detailed spectral analysis can be carried out. It reveals T-eff, log g and the metal abundance of each individual star. The cool companion is of particular interest, because its spectrum reveals the original chemical composition of the binary.},
author = {Kreuzer, Simon and Irrgang, Andreas and Heber, Ulrich},
doi = {10.1515/astro-2018-0013},
faupublication = {yes},
pages = {95-97},
peerreviewed = {unknown},
publisher = {DE GRUYTER POLAND SP ZOO},
title = {{Spectroscopy} of hot subdwarf binaries},
volume = {27},
year = {2018}
}
@inproceedings{faucris.246885576,
abstract = {Some gaps in the mosaic of binary star evolution have recently been filled by the discoveries of helium-core white dwarf progenitors (often called extremely low mass (ELM) white dwarfs) as stripped cores of first-giant branch objects. Two varieties can be distinguished. One class is made up by SB1 binaries, companions being white dwarfs as well. Another class, the so-called EL CVn stars, are composite spectrum binaries, with A-Type companions. Pulsating stars are found among both classes. A riddle is posed by the apparently single objects. There is a,one-to-one correspondence of the phenomena found for these new classes of star to those observed for sdB stars. In fact, standard evolutionary scenarios explain the origin of sdB stars as red giants that have been stripped close to the tip of first red giant branch. A subgroup of subluminous B stars can also be identified as stripped helium-cores of red giants. They form an extension of the ELM sequence to higher temperatures. Hence low mass white dwarfs of helium cores and sdB stars in binaries are close relatives in terms of stellar evolution.},
author = {Heber, Ulrich},
faupublication = {yes},
month = {Jan},
pages = {85-90},
peerreviewed = {unknown},
title = {{Stripped} {Red} {Giants} - {Helium} {Core} {White} {Dwarf} {Progenitors} and their {sdB} {Siblings}},
volume = {509},
year = {2017}
}
@article{faucris.281434251,
abstract = {Theories of planet formation give contradicting results of how frequent close-in giant planets of intermediate mass stars (IMSs; 1.3 <= M-* <= 3.2 M-circle dot) are. Some theories predict a high rate of IMSs with close-in gas giants, while others predict a very low rate. Thus, determining the frequency of close-in giant planets of IMSs is an important test for theories of planet formation. We use the CoRoT survey to determine the absolute frequency of IMSs that harbour at least one close-in giant planet and compare it to that of solar-like stars. The CoRoT transit survey is ideal for this purpose, because of its completeness for gas-giant planets with orbital periods of less than 10 d and its large sample of main-sequence IMSs. We present a high precision radial velocity follow-up programme and conclude on 17 promising transit candidates of IMSs, observed with CoRoT. We report the detection of CoRoT-34b, a brown dwarf close to the hydrogen burning limit, orbiting a 1.1 Gyr A-type main-sequence star. We also confirm two inflated giant planets, CoRoT-35b, part of a possible planetary system around a metal-poor star, and CoRoT-36b on a misaligned orbit. We find that 0.12 +/- 0.10 per cent of IMSs between 1.3 <= M-* <= 1.6 M-circle dot observed by CoRoT do harbour at least one close-in giant planet. This is significantly lower than the frequency (0.70 +/- 0.16 per cent) for solar-mass stars, as well as the frequency of IMSs harbouring long-period planets (similar to 8 per cent).},
author = {Sebastian, Daniel and Guenther, E. W. and Deleuil, M. and Dorsch, Matti and Heber, Ulrich and Heuser, Christian and Gandolfi, D. and Grziwa, S. and Deeg, H. J. and Alonso, R. and Bouchy, F. and Csizmadia, Sz and Cusano, F. and Fridlund, M. and Geier, S. and Irrgang, Andreas and Korth, J. and Nespral, D. and Rauer, H. and Tal-Or, L.},
doi = {10.1093/mnras/stac2131},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2022-09-09},
pages = {636-655},
peerreviewed = {Yes},
title = {{Sub}-stellar companions of intermediate-mass stars with {CoRoT}: {CoRoT}-34b, {CoRoT}-35b, and {CoRoT}-36b},
volume = {516},
year = {2022}
}
@article{faucris.228155984,
author = {Raddi, Roberto and Heber, Ulrich and Hollands, Mark A.},
doi = {10.1093/astrogeo/atz180},
faupublication = {yes},
journal = {Astronomy & Geophysics},
note = {CRIS-Team Scopus Importer:2019-10-22},
pages = {34-37},
peerreviewed = {Yes},
title = {{Surviving} a supernova: {Zombies} and runaways},
volume = {60},
year = {2019}
}
@article{faucris.246878840,
abstract = {We have produced simulated time series of high resolution spectroscopy for sdBs. We present the first results of testing classical mode identification techniques. Here, in particular, we analyse the behaviour of individual spectral lines and discuss the results and applicability of the moment method.},
author = {Oreiro, R. and Telting, J. H. and Ostensen, R. H. and Briquet, M. and Aerts, Conny and Heber, Ulrich and Heber, Ulrich and Vuckovic, Maja},
doi = {10.1007/s10509-010-0415-x},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Asteroseismology;Hot subdwarfs},
pages = {211-216},
peerreviewed = {Yes},
title = {{Synthetic} pulsational line profile variations},
volume = {329},
year = {2010}
}
@article{faucris.246875385,
abstract = {Context. The TESS satellite was launched in 2018 to perform high-precision photometry from space over almost the whole sky in a search for exoplanets orbiting bright stars. This instrument has opened new opportunities to study variable hot subdwarfs, white dwarfs, and related compact objects. Targets of interest include white dwarf and hot subdwarf pulsators, both carrying high potential for asteroseismology. Aims. We present the discovery and detailed asteroseismic analysis of a new g-mode hot B subdwarf (sdB) pulsator, EC 21494-7018 (TIC 278659026), monitored in TESS first sector using 120-s cadence. Methods. The TESS light curve was analyzed with standard prewhitening techniques, followed by forward modeling using our latest generation of sdB models developed for asteroseismic investigations. By simultaneously best-matching all the observed frequencies with those computed from models, we identified the pulsation modes detected and, more importantly, we determined the global parameters and structural configuration of the star. Results. The light curve analysis reveals that EC 21494-7018 is a sdB pulsator counting up to 20 frequencies associated with independent g-modes. The seismic analysis singles out an optimal model solution in full agreement with independent measurements provided by spectroscopy (atmospheric parameters derived from model atmospheres) and astrometry (distance evaluated from Gaia DR2 trigonometric parallax). Several key parameters of the star are derived. Its mass (0.391 +/- 0.009x2006;M-circle dot) is significantly lower than the typical mass of sdB stars and suggests that its progenitor has not undergone the He-core flash; therefore this progenitor could originate from a massive (greater than or similar to 2;M-circle dot) red giant, which is an alternative channel for the formation of sdBs. Other derived parameters include the H-rich envelope mass (0.0037 +/- 0.0010;M-circle dot), radius (0.1694 +/- 0.0081;R-circle dot), and luminosity (8.2 +/- 1.1;L-circle dot). The optimal model fit has a double-layered He+H composition profile, which we interpret as an incomplete but ongoing process of gravitational settling of helium at the bottom of a thick H-rich envelope. Moreover, the derived properties of the core indicate that EC 21494-7018 has burnt similar to 43% (in mass) of its central helium and possesses a relatively large mixed core (M-core;=;0.198 +/- 0.010;M-circle dot), in line with trends already uncovered from other g-mode sdB pulsators analyzed with asteroseismology. Finally, we obtain for the first time an estimate of the amount of oxygen (in mass; X(O)(core) = 0.16(-0.05)(+0.13)X(O)core=0.16-0.05+0.13$ X(\mathrm{O}){\_}{\mathrm{core}}=0.16{\_}{-0.05}<^>{+0.13} $) produced at this stage of evolution by an helium-burning core. This result, along with the core-size estimate, is an interesting constraint that may help to narrow down the still uncertain C-12(alpha,;gamma)O-16 nuclear reaction rate.},
author = {Heber, Ulrich and Charpinet, Stephane and Brassard, P. and Fontaine, G. and Van Grootel, V. and Zong, W. and Giammichele, N. and Heber, Ulrich and Bognar, Zs and Geier, S. and Green, E. M. and Hermes, J. J. and Kilkenny, D. and Ostensen, R. H. and Pelisoli, and Silvotti, R. and Telting, J. H. and Vuckovic, M. and Worters, H. L. and Baran, A. S. and Bell, K. J. and Bradley, P. A. and Debes, J. H. and Kawaler, S. D. and Kolaczek-Szymanski, P. and Murphy, S. J. and Pigulski, A. and Sodor, A. and Uzundag, M. and Handberg, Rasmus and Kjeldsen, H. and Ricker, G. R. and Vanderspek, R. K.},
doi = {10.1051/0004-6361/201935395},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {asteroseismology;stars;interiors;stars;oscillations;stars;horizontal-branch;stars;individual;TIC 278659026;subdwarfs},
peerreviewed = {Yes},
title = {{TESS} first look at evolved compact pulsators {Discovery} and asteroseismic probing of the g-mode hot {B} subdwarf pulsator {EC} 21494-7018},
volume = {632},
year = {2019}
}
@article{faucris.247099899,
abstract = {The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions such as massive white dwarfs, neutron stars, or black holes. Here we provide classifications, atmospheric parameters, and a complete radial velocity (RV) catalogue containing 1914 single measurements for a sample of 177 hot subluminous stars discovered based on SDSS DR7; 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions of hydrogen-rich hot subdwarfs in our sample to be smaller than ∼1.3%, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding ∼8 d. We detect a mismatch between the ΔRVmax-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with amplitudes of up to ∼180 km s-1 on timescales of years, days, and even hours have been detected in some He-sdO stars. They might be connected to irregular photometric variations in some cases.},
author = {Geier, S. and Kupfer, Thomas and Heber, Ulrich and Schaffenroth, Veronika and Barlow, B. N. and Ostensen, R. H. and O'Toole, S. J. and Ziegerer, Eva and Heuser, Christian and Maxted, P. F. L. and Gaensicke, B. T. and Marsh, T. R. and Napiwotzki, R. and Brünner, Patrick and Schindewolf, Markus and Niederhofer, F.},
doi = {10.1051/0004-6361/201525666},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Binaries: spectroscopic; Stars: atmospheres; Stars: horizontal-branch; Subdwarfs},
note = {CRIS-Team Scopus Importer:2020-12-21},
peerreviewed = {Yes},
title = {{The} catalogue of radial velocity variable hot subluminous stars from the {MUCHFUSS} project},
volume = {577},
year = {2015}
}
@article{faucris.246885832,
author = {Geier, S. and Kupfer, T. and Heber, Ulrich and Schaffenroth, Veronika and Barlow, B. N. and Ostensen, R. H. and O'Toole, S. J. and Ziegerer, Eva and Heuser, Christian and Maxted, P. F. L. and Gansicke, B. T. and Marsh, T. R. and Napiwotzki, R. and Brünner, Patrick and Schindewolf, Markus and Niederhofer, F.},
doi = {10.1051/0004-6361/201525666e},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {binaries: spectroscopic;subdwarfs;stars: horizontal branch;stars: atmospheres;errata, addenda},
peerreviewed = {Yes},
title = {{The} catalogue of radial velocity variable hot subluminous stars from the {MUCHFUSS} project (vol 577, pg {A26}, 2015)},
volume = {602},
year = {2017}
}
@article{faucris.227775416,
abstract = {Eclipsing post-common-envelope binaries are highly important for resolving the poorly understood, very short-lived common-envelope phase of stellar evolution. Most hot subdwarfs (sdO/Bs) are the bare helium-burning cores of red giants that have lost almost all of their hydrogen envelope. This mass loss is often triggered by common-envelope interactions with close stellar or even substellar companions. Cool companions to hot subdwarf stars such as late-type stars and brown dwarfs are detectable from characteristic light-curve variations - reflection effects and often eclipses. In the recently published catalog of eclipsing binaries in the Galactic Bulge and in the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey, we discovered 125 new eclipsing systems showing a reflection effect seen by visual inspection of the light curves and using a machine-learning algorithm, in addition to the 36 systems previously discovered by the Optical Gravitational Lesing Experiment (OGLE) team. The Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project aims at analyzing all newly discovered eclipsing binaries of the HW Vir type (hot subdwarf + close, cool companion) based on a spectroscopic and photometric follow up to derive the mass distribution of the companions, constrain the fraction of substellar companions, and determine the minimum mass needed to strip off the red-giant envelope. To constrain the nature of the primary we derived the absolute magnitude and the reduced proper motion of all our targets with the help of the parallaxes and proper motions measured by the Gaia mission and compared those to the Gaia white-dwarf candidate catalog. It was possible to derive the nature of a subset of our targets, for which observed spectra are available, by measuring the atmospheric parameter of the primary, confirming that less than 10% of our systems are not sdO/Bs with cool companions but are white dwarfs or central stars of planetary nebula. This large sample of eclipsing hot subdwarfs with cool companions allowed us to derive a significant period distribution for hot subdwarfs with cool companions for the first time showing that the period distribution is much broader than previously thought and is ideally suited to finding the lowest-mass companions to hot subdwarf stars. The comparison with related binary populations shows that the period distribution of HW Vir systems is very similar to WD+dM systems and central stars of planetary nebula with cool companions. In the future, several new photometric surveys will be carried out, which will further increase the sample of this project, providing the potential to test many aspects of common-envelope theory and binary evolution.},
author = {Schaffenroth, V. and Barlow, B. N. and Geier, S. and Vuckovic, M. and Kilkenny, D. and Wolz, Maximilian and Kupfer, T. and Heber, Ulrich and Drechsel, Horst and Kimeswenger, S. and Marsh, T. and Wolf, M. and Pelisoli, I. and Freudenthal, J. and Dreizler, S. and Kreuzer, Simon and Ziegerer, Eva},
doi = {10.1051/0004-6361/201936019},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
note = {CRIS-Team WoS Importer:2019-10-11},
peerreviewed = {Yes},
title = {{The} {EREBOS} project: {Investigating} the effect of substellar and low-mass stellar companions on late stellar evolution {Survey}, target selection, and atmospheric parameters},
volume = {630},
year = {2019}
}
@article{faucris.246890275,
abstract = {Hypervelocity stars (HVSs) travel with velocities so high that they exceed the escape velocity of the Galaxy. Several acceleration mechanisms have been discussed. Only one HVS (US 708, HVS 2) is a compact helium star. Here we present a spectroscopic and kinematic analysis of US 708. Traveling with a velocity of similar to 1200 kilometers per second, it is the fastest unbound star in our Galaxy. In reconstructing its trajectory, the Galactic center becomes very unlikely as an origin, which is hardly consistent with the most favored ejection mechanism for the other HVSs. Furthermore, we detected that US 708 is a fast rotator. According to our binary evolution model, it was spun-up by tidal interaction in a close binary and is likely to be the ejected donor remnant of a thermonuclear supernova.},
author = {Geier, Stephan and Furst, Felix and Ziegerer, Eva and Kupfer, Thomas and Heber, Ulrich and Irrgang, Andreas and Wang, Bo and Liu, Z. and Han, Z. and Sesar, B. and Levitan, D. and Kotak, R. and Magnier, E. A. and Smith, K. and Burgett, W. S. and Chambers, K. and Flewelling, H. and Kaiser, N. and Wainscoat, R and Waters, C.},
doi = {10.1126/science.1259063},
faupublication = {yes},
journal = {Science},
pages = {1126-1128},
peerreviewed = {Yes},
title = {{The} fastest unbound star in our {Galaxy} ejected by a thermonuclear supernova},
volume = {347},
year = {2015}
}
@article{faucris.310445901,
abstract = {We report the discovery of the first hot subdwarf B (sdB) star with a massive compact companion in a wide (P = 892.5 ± 60.2 d) binary system. It was discovered based on an astrometric binary solution provided by the Gaia mission Data Release 3. We performed detailed analyses of the spectral energy distribution (SED) as well as spectroscopic follow-up observations and confirm the nature of the visible component as a sdB star. The companion is invisible despite of its high mass of Mcomp = 1.50- 0.45+0.37 M·. A main sequence star of this mass would significantly contribute to the SED and can be excluded. The companion must be a compact object, either a massive white dwarf or a neutron star. Stable Roche lobe overflow to the companion likely led to the stripping of a red giant and the formation of the sdB, the hot and exposed helium core of the giant. Based on very preliminary data, we estimate that ∼9% of the sdBs might be formed through this new channel. This binary might also be the prototype for a new progenitor class of supernovae type Ia, which has been predicted by theory. },
author = {Geier, S. and Dorsch, M. and Dawson, H. and Pelisoli, I. and Munday, J. and Marsh, T. R. and Schaffenroth, V. and Heber, Ulrich},
doi = {10.1051/0004-6361/202346407},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {Binaries: general; Stars: horizontal-branch; Stars: neutron; Subdwarfs; Supernovae: general; White dwarfs},
note = {CRIS-Team Scopus Importer:2023-09-15},
peerreviewed = {Yes},
title = {{The} first massive compact companion in a wide orbit around a hot subdwarf star},
volume = {677},
year = {2023}
}
@article{faucris.246879380,
abstract = {The HYPER-MUCHFUSS project targets a population of high velocity subluminous B stars to discover either close binaries with massive unseen companions or hyper-velocity stars. Our starting point is the enormous database of SDSS. We preselected sdO/B candidates by colour and classified them by visual inspection of their spectra. We measured the radial velocity from the coadded SDSS spectra, which serves as first epoch measurement. Stars with high Galactic rest-frame velocities were selected and second epoch observations were obtained starting in 2007 at several sites. For the brighter targets we also included the SDSS individual spectra as additional information. In the course of our survey we observed 88 out of 265 stars from our target list. We discovered 39 HVS candidates as well as 49 close binaries. In addition we analysed all single spectra of sdBs from SDSS and found 120 close binaries. For the targets with constant RVs we performed a proper motion analysis with the highest possible accuracy from the available digitised photographic plates. Together with the analysed spectra and the calculation of the spectroscopic distance, we calculated complete trajectories and deduced the origins of these stars. Targets with high RV variability on short timescales were selected for follow-up. Numerical simulations based on the period and companion mass distribution of the known sdB binary sample were carried out to optimise the target selection and single out candidate binaries with massive companions. The follow-up campaign using WHT/ISIS and CAHA-3.5m/TWIN started in 2009.},
author = {Tillich, A. and Geier, S. and Heber, Ulrich and Hirsch, H. and Maxted, P. F. L. and Marsh, T. and Gansicke, B. and Napiwotzki, R. and Ostensen, R. and Scholz, R-D},
doi = {10.1007/s10509-010-0306-1},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Kinematics;Individual;Atmospheres;Line profiles},
pages = {63-68},
peerreviewed = {Yes},
title = {{The} {HYPER}-{MUCHFUSS} project-target selection and analysis},
volume = {329},
year = {2010}
}
@article{faucris.246879650,
abstract = {The HYPER-MUCHFUSS (HYPER-velocity stars or Massive Unseen Companions of Hot Faint Underluminous Stars from SDSS) project targets a population of high-velocity subluminous B stars to discover either close binaries with massive unseen companions or hyper-velocity stars. We re-observed high-velocity subdwarf selected candidates from the SDSS spectroscopic Data Release 6. Starting in 2007 we used several instruments and have now reached a completion level of 33% (from 265 targets), whereas we found at least 16 close binaries. Here we present results for two of our 39 hyper-velocity star candidates. From the available Digitized Sky Surveys photographic plates we measured a significant proper motion for 14 stars. Combining this information with a detailed spectroscopic analysis allows for the first time a complete determination of the 3D-trajectories for a high-velocity sample. We present our preliminary results for the two subdwarfs J1644+4523 and J1211+1437. Assuming the Standard Allen and Santillan (Rev. Mex. Astron. Astrofis. 22:255, 1991) potential the first one is bound and originates in the central region of the Galaxy. The subdwarf B star J1211+1437 is possibly unbound and seems to originate in the Galactic rim. We also performed numerical kinematical experiments with increased dark matter halo mass. and found that the origin of J1644+4523 in the central region is not changed but the time-of-flight is drastically shortened. J1211+1437 would be bound and probably belongs to population II.},
author = {Tillich, A. and Geier, Stephan and Heber, Ulrich and Hirsch, H. and Maxted, P. F. L. and Marsh, T. and Gaensicke, Boris T and Napiwotzki, R. and Otensen, R. and Scholz, R-D},
doi = {10.1007/s10509-010-0342-x},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Kinematics;Individual;Atmospheres;Line profiles},
pages = {69-76},
peerreviewed = {Yes},
title = {{The} {HYPER}-{MUCHFUSS} project-the constant high-velocity population},
volume = {329},
year = {2010}
}
@article{faucris.246883551,
abstract = {Hot subdwarfs (sdO/Bs) are the helium-burning cores of red giants, which have lost almost all of their hydrogen envelope. This mass loss is often triggered by common envelope interactions with close stellar or even substellar companions. Cool companions like late-type stars or brown dwarfs are detectable via characteristic light-curve variations like reflection effects and often also eclipses. To search for such objects, we obtained multi-band light curves of 26 close sdO/B binary candidates from the MUCHFUSS project with the BUSCA instrument. We discovered a new eclipsing reflection effect system (P = 0 : 168938 d) with a low-mass M dwarf companion (0.116 M-circle dot). Three more reflection effect binaries found in the course of the campaign have already been published; two of them are eclipsing systems, and in one system only showing the reflection effect but no eclipses, the sdB primary is found to be pulsating. Amongst the targets without reflection effect a new long-period sdB pulsator was discovered and irregular light variations were found in two sdO stars. The found light variations allowed us to constrain the fraction of reflection effect binaries and the substellar companion fraction around sdB stars. The minimum fraction of reflection effect systems amongst the close sdB binaries might be greater than 15% and the fraction of close substellar companions in sdB binaries may be as high as 8 .0%. This would result in a close substellar companion fraction to sdB stars of about 3%. This fraction is much higher than the fraction of brown dwarfs around possible progenitor systems, which are solar-type stars with substellar companions around 1AU, as well as close binary white dwarfs with brown dwarf companions. This might suggest that common envelope interactions with substellar objects are preferentially followed by a hot subdwarf phase.},
author = {Schaffenroth, Veronika and Geier, S. and Heber, Ulrich and Gerber, Raoul and Schneider, David and Ziegerer, Eva and Cordes, O.},
doi = {10.1051/0004-6361/201629789},
faupublication = {yes},
journal = {Astronomy & Astrophysics},
keywords = {subdwarfs;binaries: eclipsing;binaries: spectroscopic;brown dwarfs;stars: fundamental parameters},
peerreviewed = {Yes},
title = {{The} {MUCHFUSS} photometric campaign},
volume = {614},
year = {2018}
}
@article{faucris.275329103,
abstract = {Blue Large-Amplitude Pulsators (BLAPs) are a relatively new class of blue variable stars showing periodic variations in their light curves with periods shorter than a few tens of minutes and amplitudes of more than 10 per cent. We report nine blue variable stars identified in the OmegaWhite survey conducted using ESO's VST, which shows a periodic modulation in the range 7-37 min and an amplitude in the range 0.11-0.28 mag. We have obtained a series of followup photometric and spectroscopic observations made primarily using SALT and telescopes at SAAO. We find four stars which we identify as BLAPs, one of which was previously known. One star, OW J0820-3301, appears to be a member of the V361 Hya class of pulsating stars and is spatially close to an extended nebula. One further star, OW J1819-2729, has characteristics similar to the sdAV pulsators. In contrast, OW J0815-3421 is a binary star containing an sdB and a white dwarf with an orbital period of 73.7 min, making it only one of six white dwarf-sdB binaries with an orbital period shorter than 80 min. Finally, high cadence photometry of four of the candidate BLAPs show features that we compare with notch-like features seen in the much longer period Cepheid pulsators.},
author = {Ramsay, Gavin and Woudt, Patrick A. and Kupfer, Thomas and Van Roestel, Jan and Paterson, Kerry and Warner, Brian and Buckley, David A. H. and Groot, Paul J. and Heber, Ulrich and Irrgang, Andreas and Jeffery, C. Simon and Motsoaledi, Mokhine and Schwartz, Martinus J. and Wevers, Thomas},
doi = {10.1093/mnras/stac1000},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2022-05-20},
pages = {2215-2225},
peerreviewed = {Yes},
title = {{The} {OmegaWhite} survey for short-period variable stars - {VII}. {High} amplitude short-period blue variables},
volume = {513},
year = {2022}
}
@article{faucris.246892401,
abstract = {The UV-Excess survey of the northern Galactic plane images a 10 degrees x 185 degrees wide band, centred on the Galactic equator using the 2.5-m Isaac Newton Telescope in four bands (U, g, r, He 15875) down to similar to 21-22 mag (similar to 20 in He 15875). The setup and data reduction procedures are described. Simulations of the colours of main-sequence stars, giant, supergiants, DA and DB white dwarfs and AM Canum Venaticorum stars are made, including the effects of reddening. A first look at the data of the survey (currently 30 per cent complete) is given.},
author = {Groot, Paul J. and Verbeek, Kars and Greimel, Robert and Irwin, Mike and Gonzalez-Solares, Eduardo and Gaensicke, Boris T. and De Groot, Eelco and Drew, Janet and Augusteijn, Thomas and Aungwerojwit, Amornrat and Barlow, Mike and Barros, Susana and Van Den Besselaar, Else J. M. and Casares, Jorge and Corradi, Romano and Corral-Santana, Jesus M. and Deacon, Niall and Van Ham, Wilbert and Hu, Haili and Heber, Ulrich and Jonker, Peter G. and King, Rob and Knigge, Christian and Mampaso, Antonio and Marsh, Tom R. and Morales-Rueda, Luisa and Napiwotzki, Ralf and Naylor, Tim and Nelemans, Gijs and Oosting, Tim and Pyrzas, Stylianos and Pretorius, Magaretha and Rodriguez-Gil, Pablo and Roelofs, Gijs H. A. and Sale, Stuart and Schellart, Pim and Steeghs, Danny and Szyszka, Cezary and Unruh, Yvonne and Walton, Nicholas A. and Weston, Simon and Witham, Andrew and Woudt, Patrick and Zijlstra, Albert},
doi = {10.1111/j.1365-2966.2009.15273.x},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {surveys;stars: general;ISM: general;Galaxy: disc;Galaxy: stellar content;Galaxy: structure},
pages = {323-339},
peerreviewed = {Yes},
title = {{The} {UV}-{Excess} survey of the northern {Galactic} plane},
volume = {399},
year = {2009}
}
@article{faucris.246879920,
abstract = {In March 2008 we obtained 2 nights of time-resolved high-resolution spectroscopy with UVES@VLT of the pulsating sdB QQ Vir (PG1325+101), totalling more than 750 spectra. We aim to study in detail the atmospheric response to the pulsations, and to derive observational constraints on the eigenmode of the main pulsation. In this paper we present the first preliminary results.We follow the technique outlined in Telting et al. (Astron. Astrophys. 492:815, 2008) in order to obtain high-quality line-profile variations from phase-folded spectra. From the modelling of such line-profile variations we aim to derive constraints on the pulsational degree a"" and azimuthal number m of the main pulsation mode in this star.To facilitate accurate frequency determination of the pulsations in QQ Vir, and to strengthen the derivation of the degree a"" of the main mode, we organised a photometric campaign around the spectroscopic observations. This photometric campaign will be discussed in a separate contribution (Baran et al. in Astrophys. Space Sci. 2010, this volume).},
author = {Telting, J. and Ostensen, R. and Oreiro, R. and Heber, Ulrich and Vuckovic, Maja and Randall, S. and Baran, Andrzej},
doi = {10.1007/s10509-010-0333-y},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Stellar pulsations;Subdarf B stars;QQ Vir (PG1325+101);Pulsation-mode identification;Time-resolved spectroscopy;Internal stellar structure;Stellar evolution},
pages = {163-166},
peerreviewed = {Yes},
title = {{Time}-resolved high-resolution spectroscopy of the pulsating {sdB} star {QQ} {Vir} ({PG1325}+101)},
volume = {329},
year = {2010}
}
@article{faucris.246880190,
abstract = {We obtained 1955 high-resolution spectra of the high-amplitude pulsating subdwarf B star V338 Ser with the FIES spectrograph at the 2.5 m Nordic Optical Telescope covering 4 full nights in May-June 2009. Here we present the first results from phase-folding the data on the main pulsation mode, as revealed by simultaneous B-band photometry obtained with the Mercator 1.25 m and Baker 0.4 m telescopes. We compare the results with a sample line-profile model produced with LTE atmospheres and bruce+kylie.},
author = {Ostensen, R. H. and Telting, J. H. and Oreiro, R. and Heber, Ulrich and Heber, Ulrich and De Beck, Elvire and Reed, Michael},
doi = {10.1007/s10509-010-0287-0},
faupublication = {yes},
journal = {Astrophysics and Space Science},
keywords = {Subdwarfs;Pulsators;Line-profile variations},
pages = {167-174},
peerreviewed = {Yes},
title = {{Time}-resolved spectroscopy of the {sdBV} {V338} {Serpentis}},
volume = {329},
year = {2010}
}
@inproceedings{faucris.246890544,
abstract = {We use the CoRoT-survey to search for transiting close-in planets of intermediate-mass stars (M-* = 1.3 - 2.1 M-circle dot). We present recent results of our survey. RV-surveys and direct imaging campaigns showed, that intermediate-mass main-sequence stars have more massive planets then solar-like stars. Even brown dwarfs have been found. In our study we concentrated on short-period planets for which a mass-determination is possible. The detection of close-in planets of intermediate-mass stars put strong constraints on the timescales of the formation and migration. We already have identified transiting Jupiter-like planet candidates with short orbital periods and observed these candidates with high-resolution echelle-spectrographs at various Telescopes.},
author = {Sebastian, Daniel and Guenther, Eike W. and Heber, Ulrich and Geier, Stephan and Grziwa, Sascha},
doi = {10.1051/epjconf/201510106056},
faupublication = {yes},
month = {Jan},
peerreviewed = {unknown},
title = {{Transiting} {Sub}-stellar companions of {Intermediate}-mass stars},
volume = {101},
year = {2015}
}
@article{faucris.270692354,
abstract = {As part of a survey to find close binary systems among central stars of planetary nebula, we present two newly discovered binary systems. GALEX J015054.4+310745 is identified as the central star of the possible planetary nebula Fr 2-22. We find it to be a single-lined spectroscopic binary with an orbital period of 0.2554435(10) d. We support the previous identification of GALEX J015054.4+310745 as an sdB star and provide physical parameters for the star from spectral modelling. We identify its undetected companion as a likely He white dwarf. Based on this information, we find it unlikely that Fr 2-22 is a true planetary nebula. In addition, the central star of the true planetary nebula Hen 2-84 is found to be a photometric variable, likely due to the irradiation of a cool companion. The system has an orbital period of 0.485645(30) d. We discuss limits on binary parameters based on the available light-curve data. Hen 2-84 is a strongly shaped bipolar planetary nebula, which we now add to the growing list of axially or point-symmetric planetary nebulae with a close binary central star.},
author = {Hillwig, Todd C. and Reindl, Nicole and Rotter, Hannah M. and Rengstorf, Adam W. and Heber, Ulrich and Irrgang, Andreas},
doi = {10.1093/mnras/stac226},
faupublication = {yes},
journal = {Monthly Notices of the Royal Astronomical Society},
note = {CRIS-Team WoS Importer:2022-03-11},
pages = {2033-2039},
peerreviewed = {Yes},
title = {{Two} evolved close binary stars: {GALEX} {J015054}.4+310745 and the central star of the planetary nebula {Hen} 2-84},
volume = {511},
year = {2022}
}