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          Institute: MPI für Kernphysik     Collection: High-Energy Astrophysics     Display Documents

ID: 522336.0, MPI für Kernphysik / High-Energy Astrophysics
Discovery of VHE γ-rays from the BL Lacertae object PKS 0548–322
Authors:Aharonian, F.; Akhperjanian, A. G.; Anton, G.; de Almeida, U. B.; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Bernlöhr, K.; Boisson, C.; Bochow, A.; Borrel, V.; Brun, F.; Benbow, Wystan; Brucker, J.; Brun, P.; Bühler, R.; Bulik, T.; Büsching, I.; Boutelier, T.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L. M.; Clapson, A. C.; Coignet, G.; Dalton, M.; Daniel, M. K.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Atai, A.; Domainko, W.; Drury, L. O.; Dubois, F.; Dubus, G.; Dyks, J.; Dyrda, M.; Egberts, K.; Emmanoulopoulos, D.; Espigat, P.; Farnier, C.; Feinstein, F.; Fiasson, A.; Förster, A.; Fontaine, G.; Fussling, M.; Gabici, S.; Gallant, Y. A.; Gerard, L.; Giebels, B.; Glicenstein, J. F.; Gluck, B.; Goret, P.; Hauser, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Holleran, M.; Hoppe, S.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jung, I.; Katarzynski, K.; Katz, U.; Kaufmann, S.; Kendziorra, E.; Kerschhaggl, M.; Khangulyan, D.; Khelifi, B.; Keogh, D.; Komin, N.; Kosack, K.; Lamanna, G.; Lenain, J. P.; Lohse, T.; Marandon, V.; Martin, J. M.; Martineau-Huynh, O.; Marcowith, A.; Maurin, D.; McComb, T. J. L.; Medina, M. C.; Moderski, R.; Moulin, E.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Niemiec, J.; Nolan, S. J.; Ohm, S.; Olive, J. F.; Wilhelmi, E. D.; Orford, K. J.; Ostrowski, M.; Panter, M.; Paz Arribas, M. P.; Pedaletti, G.; Pelletier, G.; Petrucci, P. O.; Pita, S.; Puhlhofer, G.; Punch, M.; Quirrenbach, A.; Raubenheimer, B. C.; Raue, M.; Rayner, S. M.; Renaud, M.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schock, F. M.; Schroder, R.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Skilton, J. L.; Sol, H.; Spangler, D.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Superina, G.; Szostek, A.; Tam, P. H.; Tavernet, J. P.; Terrier, R.; Tibolla, O.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Venter, L.; Vialle, J. P.; Vincent, P.; Vivier, M.; Völk, H. J.; Volpe, F.; Wagner, S. J.; Ward, M.; Zdziarski, A. A.; Zech, A.; Bolomont, J.; Davids, I.; Gerbig, D.; Göring, D.; Jahn, C.; Kluzniak, W.; Kneiske, T.; Masbou, J.; Nicholas, B; Sikora, M.; Stinzing, F.; Tluczykont, M.
Date of Publication (YYYY-MM-DD):2010-10
Title of Journal:Astronomy & Astrophysics
Journal Abbrev.:Astron. Astrophys.
Start Page:1
End Page:6
Sequence Number of Article:A69
Copyright:© ESO, 2010
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Aims. PKS 0548–322 (z = 0.069) is a “high-frequency-peaked” BL Lac object and a candidate very high energy (VHE, E > 100 GeV) γ-ray emitter, due to its high X-ray and radio flux. Observations at the VHE band provide insights into the origin of very energetic particles present in this source and the radiation processes at work.

Methods. We report observations made between October 2004 and January 2008 with the HESS array, a four imaging atmospheric-Cherenkov telescopes. Contemporaneous UV and X-ray observations with the Swift satellite in November 2006 are also reported.

Results. PKS 0548-322 is detected for the first time in the VHE band with HESS We measure an excess of 216 γ-rays corresponding to a significance of 5.6 standard deviations. The photon spectrum of the source is described by a power-law, with a photon index of Γ = 2.86 ± 0.34stat ± 0.10sys. The integral flux above 200 GeV is ~1.3% of the flux of the Crab Nebula, and is consistent with being constant in time. Contemporaneous Swift/XRT observations reveal an X-ray flux between 2 and 10 keV of F2-10 keV = (2.3±0.2)×10-11 erg cm-2 s-1, an intermediate intensity state with respect to previous observations. The spectral energy distribution can be reproduced using a simple one-zone synchrotron self Compton model, with parameters similar those observed for other sources of this type.
Free Keywords:gamma rays: observations / galaxies: active / BL Lacertae objects: individual: PKS 0548-322
External Publication Status:published
Document Type:Article
Affiliations:MPI für Kernphysik/Group of W. Hofmann/Experimental High-Energy Astrophysics (M. Panter, G. Hermann)
MPI für Kernphysik/Group of W. Hofmann/High Energy Astrophysics (F. Aharonian)
External Affiliations:Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
5 University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
6 Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, 9 av. du Colonel Roche, BP 4346, 31029 Toulouse Cedex 4, France
Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis Diderot, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France (UMR 7164 (CNRS, Université Paris VII, CEA, Observatoire de Paris).)
8 Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
9 Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
10 LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
11 LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 place Jussieu, 75252 Paris Cedex 5, France
12 IRFU/DSM/CEA, CE Saclay, 91191 Gif-sur-Yvette, Cedex, France
13 Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
14 Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
15 Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France e-mail: gilles.henri@obs.ujf-grenoble.fr
16 Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
17 Laboratoire d'Annecy-le-Vieux de Physique des Particules, Université de Savoie, CNRS/IN2P3, 74941 Annecy-le-Vieux, France
18 University of Namibia, Private Bag 13301, Windhoek, Namibia
19 Instytut Fizyki Jądrowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
20 Laboratoire de Physique Théorique et Astroparticules, Université Montpellier 2, CNRS/IN2P3, CC 70, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
21 Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
22 Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
23 School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
24 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
25 Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń, Poland
26 Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague, Czech Republic
27 School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia
28 European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
29 Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
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