Abramowski, A. and Aharonian, F. and Ait Benkhali, F. and Akhperjanian, A.G. and Angüner, E. and Anton, G. 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 Cerruti, M. 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 Lennarz, D. 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 de Naurois, M. and Niemiec, J. and Nolan, S.J. and Oakes, L. and Ohm, S. and de Oña Wilhelmi, E. 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 Reimer, A. and Reimer, O. and Renaud, M. and de los Reyes, R. 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 Szostek, A. 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 Ward, M. and Weidinger, M. and Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Wörnlein, A. and Wouters, D. and Zabalza, V. and Zacharias, M. and Zajczyk, A. and Zdziarski, A.A. and Zech, A. and Zechlin, H.-S. (2014) 'Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011.', Astronomy and astrophysics., 564 . A9.
Context. About 40% of the observation time of the High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim of increasing the sample of known extragalactic very-high-energy (VHE, E > 100 GeV) sources and constraining the physical processes at play in potential emitters. Aims. H.E.S.S. observations of AGN, spanning a period from April 2004 to December 2011, are investigated to constrain their γ-ray fluxes. Only the 47 sources without significant excess detected at the position of the targets are presented. Methods. Upper limits on VHE fluxes of the targets were computed and a search for variability was performed on the nightly time scale. Results. For 41 objects, the flux upper limits we derived are the most constraining reported to date. These constraints at VHE are compared with the flux level expected from extrapolations of Fermi-LAT measurements in the two-year catalog of AGN. The H.E.S.S. upper limits are at least a factor of two lower than the extrapolated Fermi-LAT fluxes for 11 objects. Taking into account the attenuation by the extragalactic background light reduces the tension for all but two of them, suggesting intrinsic curvature in the high-energy spectra of these two AGN. Conclusions. Compilation efforts led by current VHE instruments are of critical importance for target-selection strategies before the advent of the Cherenkov Telescope Array (CTA).
|Keywords:||Gamma rays: galaxies, Galaxies: active.|
|Full text:||(VoR) Version of Record|
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|Publisher Web site:||http://dx.doi.org/10.1051/0004-6361/201322897|
|Publisher statement:||Reproduced with permission from Astronomy & Astrophysics, © ESO|
|Date accepted:||No date available|
|Date deposited:||15 July 2014|
|Date of first online publication:||April 2014|
|Date first made open access:||No date available|
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