VHE γ-ray emission of PKS2155-304: Spectral and temporal variability

van Eldik C, Abramowski A, Acero F, Aharonian F, Akhperjanian AG, Anton G, De Almeida UB, Bazer-Bachi AR, Becherini Y, Behera B, Benbow W, Bernloehr K, Bochow A, Boisson C, Bolmont J, Borrel V, Brucker J, Brun F, Brun P, Buehler R, Bulik T, Buesching I, Boutelier T, Chadwick PM, Charbonnier A, Chaves RCG, Cheesebrough A, Chounet LM, Clapson AC, Coignet G, Conrad J, Costamante L, Dalton M, Daniel MK, Davids ID, Degrange B, Deil C, Dickinson HJ, Djannati-Atai A, Domainko W, Drury LO, Dubois F, Dubus G, Dyks J, Dyrda M, Egberts K, Eger P, Espigat P, Fallon L, Farnier C, Fegan S, Feinstein F, Fernandes MV, Fiasson A, Foerster A, Fontaine G, Fuessling M, Gabici S, Gallant YA, Gerard L, Gerbig D, Giebels B, Glicenstein JF, Glueck B, Goret P, Göring D, Hampf D, Hauser M, Heinz S, Heinzelmann G, Henri G, Hermann G, Hinton JA, Hoffmann A, Hofmann W, Hofverberg P, Holleran M, Hoppe S, Horns D, Jacholkowska A, De Jager OC, Jahn C, Jung I, Katarzynski K, Katz U, Kaufmann S, Kerschhaggl M, Khangulyan D, Khelifi B, Keogh D, Klochkov D, Kluzniak W, Kneiske T, Komin N, Kosack K, Kossakowski R, Lamanna G, Lenain JP, Lohse T, Lu CC, Marandon V, Marcowith A, Masbou J, Maurin D, Mccomb TJL, Medina MC, Mehault J, Moderski R, Moulin E, Naumann-Godo M, De Naurois M, Nedbal D, Nekrassov D, Nguyen N, Nicholas B, Niemiec J, Nolan SJ, Ohm S, Olive JF, Wilhelmi EDO, Opitz B, Orford KJ, Ostrowski M, Panter M, Arribas MP, Pedaletti G, Pelletier G, Petrucci PO, Pita S, Puehlhofer G, Punch M, Quirrenbach A, Raubenheimer BC, Raue M, Rayner SM, Reimer O, Renaud M, De Los Reyes R, Rieger F, Ripken J, Rob L, Rosier-Lees S, Rowell G, Rudak B, Rulten CB, Ruppel J, Ryde F, Sahakian V, Santangelo A, Schlickeiser R, Schoeck FM, Schoenwald A, Schwanke U, Schwarzburg S, Schwemmer S, Shalchi A, Sushch I, Sikora M, Skilton JL, Sol H, Stawarz L, Steenkamp R, Stegmann C, Stinzing F, Superina G, Szostek A, Tam PH, Tavernet JP, Terrier R, Tibolla O, Tluczykont M, Valerius K, Van Eldik C, Vasileiadis G, Venter C, Venter L, Vialle JP, Viana A, Vincent P, Vivier M, Voelk HJ, Volpe F, Vorobiov S, Wagner SJ, Ward M, Zdziarski AA, Zech A, Zechlin HS (2010)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2010

Journal

Publisher: EDP Sciences

Book Volume: 520

Pages Range: A83

Article Number: aa14484-10

Journal Issue: 13

DOI: 10.1051/0004-6361/201014484

Abstract

Context. Observations of very high-energy γ-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects lead to a better understanding of the mechanisms in play. Aims. To investigate the spectral and temporal variability of VHE (>100 GeV) γ-rays of the well-known high-frequency-peaked BL Lac object PKS 2155-304 with the HESS imaging atmospheric Cherenkov telescopes over a wide range of flux states. Methods. Data collected from 2005 to 2007 were analyzed. Spectra were derived on time scales ranging from 3 years to 4 min. Light curve variability was studied through doubling timescales and structure functions and compared with red noise process simulations. Results. The source was found to be in a low state from 2005 to 2007, except for a set of exceptional flares that occurred in July 2006. The quiescent state of the source is characterized by an associated mean flux level of (4.32 ± 0.09 ± 0.86) × 10 cm s above 200 GeV, or approximately 15\% of the Crab Nebula, and a power-law photon index of Γ = 3.53 ± 0.06 ± 0.10. During the flares of July 2006, doubling timescales of ∼2 min are found. The spectral index variation is examined over two orders of magnitude in flux, yielding different behavior at low and high fluxes, which is a new phenomenon in VHE γ-ray emitting blazars. The variability amplitude characterized by the fractional rms F is strongly energy-dependent and is E. The light curve rms correlates with the flux. This is the signature of a multiplicative process that can be accounted for as a red noise with a Fourier index of ∼2. Conclusions. This unique data set shows evidence of a low-level γ-ray emission state from PKS 2155-304 that possibly has a different origin than the outbursts. The discovery of the light curve lognormal behavior might be an indicator of the origin of aperiodic variability in blazars. © ESO, 2010.

Authors with CRIS profile

Involved external institutions

University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) Noordwes-Universiteit / North-West University South Africa (ZA) Université Joseph Fourier (UJF Grenoble 1) France (FR) École Polytechnique - Université Paris-Saclay France (FR) Humboldt-Universität zu Berlin Germany (DE) University of Montpellier / Université Montpellier France (FR) Universität Hamburg (UHH) Germany (DE) University of Leicester United Kingdom (GB) Max-Planck-Institut für Kernphysik (MPIK) / Max Planck Institute for Nuclear Physics Germany (DE) Durham University United Kingdom (GB) Eberhard Karls Universität Tübingen Germany (DE) Ruhr-Universität Bochum (RUB) Germany (DE) Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences Poland (PL) Yerevan Physics Institute (YerPhI) / Երևանի Ֆիզիկայի Ինստիտուտ Armenia (AM) Commissariat à l'énergie atomique France (FR) University of Savoy Mont Blanc / Université Savoie Mont Blanc France (FR) Stockholm University / Stockholms universitet Sweden (SE) Institute of Nuclear Physics PAN / Instytut Fizyki Jądrowej im. Henryka Niewodniczańskiego PAN Poland (PL) Université Toulouse III - Paul Sabatier France (FR) Ruprecht-Karls-Universität Heidelberg Germany (DE) University of Warsaw / Uniwersytet Warszawski Poland (PL) Dublin Institute for Advanced Studies (DIAS) Ireland (IE) Nicolaus Copernicus University (NCU) / Uniwersytet Mikołaja Kopernika w Toruniu (UMK) Poland (PL) Univerzita Karlova v Praze / Charles University in Prague Czech Republic (CZ) University of Adelaide Australia (AU) Jagiellonian University / Uniwersytet Jagielloński (UJ) Poland (PL) Leopold-Franzens-Universität Innsbruck / University of Innsbruck Austria (AT) Royal Institute of Technology / Kungliga Tekniska Högskolan (KTH) Sweden (SE) University of Leeds United Kingdom (GB) University of Namibia (UNAM) Namibia (NA)

How to cite

APA:

van Eldik, C., Abramowski, A., Acero, F., Aharonian, F., Akhperjanian, A.G., Anton, G.,... Zechlin, H.-S. (2010). VHE γ-ray emission of PKS2155-304: Spectral and temporal variability. Astronomy & Astrophysics, 520(13), A83. https://doi.org/10.1051/0004-6361/201014484

MLA:

van Eldik, Christopher, et al. "VHE γ-ray emission of PKS2155-304: Spectral and temporal variability." Astronomy & Astrophysics 520.13 (2010): A83.

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