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Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift.

Abramowski, A. and Acero, F. and Akhperjanian, A.G. and Anton, G. and Balenderan, S. and Balzer, A. and Barnacka, A. and Becherini, Y. and Becker Tjus, J. and Behera, B. and Bernlöhr, K. and Birsin, E. and Biteau, J. 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 Chaves, R.C.G. and Cheesebrough, A. and Colafrancesco, S. and Cologna, G. and Conrad, J. and Couturier, C. and Dalton, M. and Daniel, M.K. and Davids, I.D. and Degrange, B. and Deil, C. and Dickinson, H.J. and Djannati-Ataï, A. and Domainko, W. and O'C.Drury, L. and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Egberts, K. and Eger, P. and Espigat, P. and Fallon, L. 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 Gast, H. and Giebels, B. and Glicenstein, J.F. and Glück, B. and Göring, D. and Grondin, M.-H. and Grudzińska, M. and Häffner, S. and Hague, J.D. and Hahn, J. and Hampf, D. and Harris, J. and Heinz, S. and Heinzelmann, G. and Henri, G. and Hermann, G. and Hillert, A. and Hinton, J.A. and Hofmann, W. and Holler, M. and Horns, D. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Jung, I. and Kastendieck, M.A. and Katarzyński, K. and Katz, U. and Kaufmann, S. and Khélifi, B. and Klepser, S. and Klochkov, D. and Kluźniak , W. and Kneiske, T. and Kolitzus, D. and Komin, N. and Kosack, K. and Kossakowski, R. and Krayzel, F. and Krüger, P.P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. 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 Masbou, J. and Maurin, G. and Maxted, N. and Mayer, M. and McComb, T.J.L. and Medina, M.C. and Méhault, J. and Menzler, U. and Moderski, R. and Mohamed, M. and Moulin, E. and Naumann, C.L. and de Naurois, M. and Nedbal, D. and Nguyen, N. and Niemiec, J. and Nolan, S.J. 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 Pelletier, G. and Perez, J. and Petrucci, P.-O. and Peyaud, B. and Pita, S. 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 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 Schulz, A. and Schwanke, U. and Schwarzburg, S. and Schwemmer, S. and Sheidaei, F. and Skilton, J.L. and Sol, H. and Spengler, G. 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 Terrier, R. and Tluczykont, M. and Trichard, C. and Valerius, K. and van Eldik, C. and Vasileiadis, G. and Venter, C. and Viana, A. and Vincent, P. and Völk, H.J. and Volpe, F. and Vorobiov, S. and Vorster, M. and Wagner, S.J. and Ward, M. and White, R. and deWilt, P. and Wierzcholska, A. and Wouters, D. and Zacharias, M. and Zajczyk, A. and Zdziarski, A.A. and Zech, A. and Zechlin, H.-S. and Pelat, D. and Bochow, A. and Hofverberg, P. and Naumann-Godo, M. and Pekeur, N.W. and Ripken, J. (2013) 'Discovery of TeV γ-ray emission from PKS 0447-439 and derivation of an upper limit on its redshift.', Astronomy and astrophysics., 552 . A118.


Very high-energy γ-ray emission from PKS 0447−439 was detected with the H.E.S.S. Cherenkov telescope array in December 2009. This blazar is one of the brightest extragalactic objects in the Fermi bright source list and has a hard spectrum in the MeV to GeV range. In the TeV range, a photon index of 3.89 ± 0.37 (stat) ±0.22 (sys) and a flux normalisation at 1 TeV, Φ1 TeV = (3.5 ± 1.1(stat) ± 0.9(sys)) × 10-13 cm-2   s-1   TeV-1 were found. The detection with H.E.S.S. triggered observations in the X-ray band with the Swift and RXTE telescopes. Simultaneous UV and optical data from Swift UVOT and data from the optical telescopes ATOM and ROTSE are also available. The spectrum and light curve measured with H.E.S.S. are presented and compared to the multi-wavelength data at lower energies. A rapid flare is seen in the Swift XRT and RXTE data, together with a flux variation in the UV band, at a time scale of the order of one day. A firm upper limit of z < 0.59 on the redshift of PKS 0447−439 is derived from the combined Fermi-LAT and H.E.S.S. data, given the assumptions that there is no upturn in the intrinsic spectrum above the Fermi-LAT energy range and that absorption on the extragalactic background light (EBL) is not weaker than the lower limit provided by current models. The spectral energy distribution is well described by a simple one-zone synchrotron self-Compton scenario, if the redshift of the source is less than z ≲ 0.4.

Item Type:Article
Keywords:Galaxies: active, BL Lacertae objects: individual: PKS 0447-439, Radiation mechanisms: non-thermal, Gamma rays: galaxies.
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Publisher statement:Reproduced with permission from Astronomy & Astrophysics, © ESO
Date accepted:05 March 2013
Date deposited:15 July 2014
Date of first online publication:April 2013
Date first made open access:No date available

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