%0 Journal Article
%T VHE gamma-ray emission of PKS 2155-304: spectral and temporal variability
%+ Laboratoire de Physique Théorique et Astroparticules (LPTA)
%+ Centre d'étude spatiale des rayonnements (CESR)
%+ AstroParticule et Cosmologie (APC (UMR_7164))
%+ Laboratoire Univers et Théories (LUTH (UMR_8102))
%+ Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE)
%+ Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU)
%+ Laboratoire d'Astrophysique de Grenoble (LAOG)
%+ Laboratoire Leprince-Ringuet (LLR)
%+ Laboratoire d'Annecy de Physique des Particules (LAPP)
%+ APC - Astrophysique des Hautes Energies (APC - AHE)
%A Abramowski, A.
%A Acero, Fabio
%A Aharonian, F.
%A Akhperjanian, A. G.
%A Anton, G.
%A de Almeida, U. Barres
%A Bazer-Bachi, A. R.
%A Becherini, Y.
%A Behera, B.
%A Benbow, W.
%A Bernlohr, K.
%A Bochow, A.
%A Boisson, C.
%A Bolmont, J.
%A Borrel, V.
%A Brucker, J.
%A Brun, F.
%A Brun, P.
%A Buhler, R.
%A Bulik, T.
%A Busching, I.
%A Boutelier, T.
%A Chadwick, P. M.
%A Charbonnier, A.
%A Chaves, R. C. G.
%A Cheesebrough, A.
%A Conrad, J.
%A Chounet, L. -M.
%A Clapson, A. C.
%A Coignet, G.
%A Costamante, L.
%A Dalton, M.
%A Daniel, M. K.
%A Davids, I. D.
%A Degrange, B.
%A Deil, C.
%A Dickinson, H. J.
%A Djannati-Ataï, A.
%A Domainko, W.
%A Drury, L. O'C.
%A Dubois, F.
%A Dubus, G.
%A Dyks, J.
%A Dyrda, M.
%A Egberts, K.
%A Eger, P.
%A Espigat, P.
%A Fallon, L.
%A Farnier, C.
%A Fegan, S.
%A Feinstein, F.
%A Fernandes, M. V.
%A Fiasson, A.
%A Foerster, A.
%A Fontaine, G.
%A Fussling, M.
%A Gabici, S.
%A Gallant, Y. A.
%A Gerard, L.
%A Gerbig, D.
%A Giebels, B.
%A Glicenstein, J. F.
%A Glueck, B.
%A Goret, P.
%A Goering, D.
%A Hampf, D.
%A Hauser, M.
%A Heinz, S.
%A Heinzelmann, G.
%A Henri, G.
%A Hermann, G.
%A Hinton, J. A.
%A Hoffmann, A.
%A Hofmann, W.
%A Hofverberg, P.
%A Holleran, M.
%A Hoppe, S.
%A Horns, D.
%A Jacholkowska, A.
%A de Jager, O. C.
%A Jahn, C.
%A Jung, I.
%A Katarzynski, K.
%A Katz, U.
%A Kaufmann, S.
%A Kerschhaggl, M.
%A Khangulyan, D.
%A Khelifi, B.
%A Keogh, D.
%A Klochkov, D.
%A Kluzniak, W.
%A Kneiske, T.
%A Komin, Nu.
%A Kosack, K.
%A Kossakowski, R.
%A Lamanna, G.
%A Lenain, J. -P.
%A Lohse, T.
%A Lu, C. -C.
%A Marandon, V.
%A Marcowith, A.
%A Masbou, Julien
%A Maurin, D.
%A Mccomb, T. J. L.
%A Medina, M. C.
%A Mehault, J.
%A Moderski, R.
%A Moulin, Emmanuel
%A Naumann-Godo, M.
%A de Naurois, M.
%A Nedbal, D.
%A Nekrassov, D.
%A Nguyen, N.
%A Nicholas, B.
%A Niemiec, J.
%A Nolan, S. J.
%A Ohm, S.
%A Olive, J-F.
%A Wilhelmi, E. de Ona
%A Opitz, B.
%A Orford, K. J.
%A Ostrowski, M.
%A Panter, M.
%A Arribas, M. Paz
%A Pedaletti, G.
%A Pelletier, G.
%A Petrucci, P. -O.
%A Pita, S.
%A Puehlhofer, G.
%A Punch, M.
%A Quirrenbach, A.
%A Raubenheimer, B. C.
%A Raue, M.
%A Rayner, S. M.
%A Reimer, O.
%A Renaud, M.
%A Reyes, R. de Los
%A Rieger, F.
%A Ripken, J.
%A Rob, L.
%A Rosier-Lees, S.
%A Rowell, G.
%A Rudak, B.
%A Rulten, C. B.
%A Ruppel, J.
%A Ryde, F.
%A Sahakian, V.
%A Santangelo, A.
%A Schlickeiser, R.
%A Schoeck, F. M.
%A Schoenwald, A.
%A Schwanke, U.
%A Schwarzburg, S.
%A Schwemmer, S.
%A Shalchi, A.
%A Sushch, I.
%A Sikora, M.
%A Skilton, J. L.
%A Sol, H.
%A Stawarz, L.
%A Steenkamp, R.
%A Stegmann, C.
%A Stinzing, F.
%A Superina, G.
%A Szostek, A.
%A Tam, P. H.
%A Tavernet, J. -P.
%A Terrier, R.
%A Tibolla, O.
%A Tluczykont, M.
%A Valerius, K.
%A van Eldik, C.
%A Vasileiadis, G.
%A Venter, C.
%A Venter, L.
%A Vialle, J. P.
%A Viana, A.
%A Vincent, P.
%A Vivier, M.
%A Voelk, H. J.
%A Volpe, F.
%A Vorobiov, S.
%A Wagner, S. J.
%A Ward, M.
%A Zdziarski, A. A.
%A Zech, A.
%A Zechlin, H. -S.
%Z 17 pages, 13 figures, Accepted for publication to Astronomy & Astrophysics
%< avec comité de lecture
%@ 0004-6361
%J Astronomy and Astrophysics - A&A
%I EDP Sciences
%V 520
%P A83
%8 2010
%D 2010
%Z 1005.3702
%R 10.1051/0004-6361/201014484
%Z Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]
%Z Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]Journal articles
%X Observations of very high energy gamma-rays from blazars provide information about acceleration mechanisms occurring in their innermost regions. Studies of variability in these objects allow a better understanding of the mechanisms at play. To investigate the spectral and temporal variability of VHE (>100 GeV) gamma-rays of the well-known high-frequency-peaked BL Lac object PKS 2155-304 with the H.E.S.S. imaging atmospheric Cherenkov telescopes over a wide range of flux states. Data collected from 2005 to 2007 are analyzed. Spectra are derived on time scales ranging from 3 years to 4 minutes. Light curve variability is studied through doubling timescales and structure functions, and is compared with red noise process simulations. The source is found to be in a low state from 2005 to 2007, except for a set of exceptional flares which occurred in July 2006. The quiescent state of the source is characterized by an associated mean flux level of 4.32 +/-0.09 x 10^-11 cm^-2 s^-1 above 200 GeV, or approximately 15% of the Crab Nebula, and a power law photon index of 3.53 +/-0.06. 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 behaviour at low and high fluxes,which is a new phenomenon in VHE gamma-ray emitting blazars. The variability amplitude characterized by the fractional r.m.s. is strongly energy-dependent and is proportional to E^(0.19 +/- 0.01). The light curve r.m.s. correlates with the flux. This is the signature of a multiplicative process which can be accounted for as a red noise with a Fourier index of ~2. This unique data set shows evidence for a low level gamma-ray emission state from PKS 2155-304, which possibly has a different origin than the outbursts. The discovery of the light curve lognormal behaviour might be an indicator ..
%G English
%Z HESS
%L in2p3-00496200
%U https://hal.in2p3.fr/in2p3-00496200
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