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The high-energy γ-ray emission of AP Librae.

H.E.S.S.Collaboration, and Abramowski, A. and Aharonian, F. and Ait Benkhali, F. and Akhperjanian, A.G. and Angüner, E. and Anton, G. and Backes, M. and Balenderan, S. and Balzer, A. and Barnacka, A. and Becherini, Y. and Becker Tjus, J. and Bernlöhr, K. and Birsin, E. and Bissaldi, E. and Biteau, J. and Böttcher, M. and Boisson, C. and Bolmont, J. and Bordas, P. and Brucker, J. and Brun, F. and Brun, P. and Bulik, T. and Carrigan, S. and Casanova, S. and Chadwick, P.M. and Chalme-Calvet, R. and Chaves, R.C.G. and Cheesebrough, A. and Chrétien, M. and Colafrancesco, S. and Cologna, G. and Conrad, J. and Couturier, C. and Cui, Y. and Dalton, M. and Daniel, M.K. and Davids, I.D. and Degrange, B. and Deil, C. and deWilt, P. and Dickinson, H.J. and Djannati-Ataï, A. and Domainko, W. and Drury, L.O'C. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, K. and Eger, P. and Espigat, P. and Farnier, C. and Fegan, S. and Feinstein, F. and Fernandes, M.V. and Fernandez, D. and Fiasson, A. and Fontaine, G. and Förster, A. and Füßling, M. and Gajdus, M. and Gallant, Y.A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J.F. and Grondin, M.-H. and Grudzińska, M. and Häffner, S. and Hahn, J. and Harris, J. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hervet, O. and Hillert, A. and Hinton, J.A. and Hofmann, W. and Hofverberg, P. and Holler, M. and Horns, D. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung, I. and Kastendieck, M.A. and Katarzyński, K. and Katz, U. and Kaufmann, S. and Khélifi, B. and Kieffer, M. and Klepser, S. and Klochkov, D. and Kluźniak, W. and Kneiske, T. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Krayzel, F. and Krüger, P.P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. and Lemière, A. and Lemoine-Goumard, M. and Lenain, J.-P. and Lohse, T. and Lopatin, A. and Lu, C.-C. and Marandon, V. and Marcowith, A. and Marx, R. and Maurin, G. and Maxted, N. and Mayer, M. and McComb, T.J.L. and Méhault, J. and Meintjes, P.J. and Menzler, U. and Meyer, M. and Moderski, R. and Mohamed, M. and Moulin, E. and Murach, T. and Naumann, C.L. and Naurois, M. de and Niemiec, J. and Nolan, S.J. and Oakes, L. and Odaka, H. and Ohm, S. and Oña Wilhelmi, E. de and Opitz, B. and Ostrowski, M. and Oya, I. and Panter, M. and Parsons, R.D. and Paz Arribas, M. and Pekeur, N.W. and Pelletier, G. and Perez, J. and Petrucci, P.-O. and Peyaud, B. and Pita, S. and Poon, H. and Pühlhofer, G. and Punch, M. and Quirrenbach, A. and Raab, S. and Raue, M. and Reichardt, I. and Reimer, A. and Reimer, O. and Renaud, M. and Reyes, R. de los and Rieger, F. and Rob, L. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C.B. and Sahakian, V. and Sanchez, D.A. and Santangelo, A. and Schlickeiser, R. and Schüssler, F. and Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sol, H. and Spengler, G. and Spies, F. and Stawarz, Ł. and Steenkamp, R. and Stegmann, C. and Stinzing, F. and Stycz, K. and Sushch, I. and Tavernet, J.-P. and Tavernier, T. and Taylor, A.M. and Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van Eldik, C. and van Soelen, B. and Vasileiadis, G. and Venter, C. and Viana, A. and Vincent, P. and Völk, H.J. and Volpe, F. and Vorster, M. and Vuillaume, T. and Wagner, S.J. and Wagner, P. and Wagner, R.M. and Ward, M. and Weidinger, M. and Weitze, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Wörnlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zacharias, M. and Zdziarski, A.A. and Zech, A. and Zechlin, H.-S. and Finke, J. and Fortin, P. and Horan, D. (2015) 'The high-energy γ-ray emission of AP Librae.', Astronomy & astrophysics., 573 . A31.

Abstract

The γ-ray spectrum of the low-frequency-peaked BL Lac (LBL) object AP Librae is studied, following the discovery of very-high-energy (VHE; E> 100 GeV) γ-ray emission up to the TeV range by the H.E.S.S. experiment. This makes AP Librae one of the few VHE emitters of the LBL type. The measured spectrum yields a flux of (8.8 ± 1.5stat ± 1.8sys) × 10-12 cm-2 s-1 above 130 GeV and a spectral index of Γ = 2.65 ± 0.19stat ± 0.20sys. This study also makes use of Fermi-LAT  observations in the high energy (HE, E> 100 MeV) range, providing the longest continuous light curve (5 years) ever published on this source. The source underwent a flaring event between MJD 56 306–56 376 in the HE range, with a flux increase of a factor of 3.5 in the 14 day bin light curve and no significant variation in spectral shape with respect to the low-flux state. While the H.E.S.S.  and (low state) Fermi-LAT fluxes are in good agreement where they overlap, a spectral curvature between the steep VHE spectrum and the Fermi-LAT  spectrum is observed. The maximum of the γ-ray emission in the spectral energy distribution is located below the GeV energy range.

Item Type:Article
Keywords:Galaxies: active, BL Lacertae objects: individual: AP Librae, Gamma rays: galaxies.
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1051/0004-6361/201321436
Publisher statement:Reproduced with permission from Astronomy & Astrophysics, © ESO, 2014.
Date accepted:20 October 2014
Date deposited:22 April 2015
Date of first online publication:January 2015
Date first made open access:No date available

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