Discovery of VHE gamma-rays from the BL Lac object PKS 0548-322
Abstract
PKS 0548-322 (z=0.069) is a ``high-frequency-peaked'' BL Lac object and a candidate very high energy (VHE, E>100 GeV) gamma-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. We report observations made between October 2004 and January 2008 with the H.E.S.S. array, a four imaging atmospheric-Cherenkov telescopes. Contemporaneous UV and X-ray observations with the Swift satellite in November 2006 are also reported. PKS 0548-322 is detected for the first time in the VHE band with H.E.S.S. We measure an excess of 216 gamma-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 Gamma=2.86 +/- 0.34 (stat) +/- 0.10 (sys). 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 F_{2-10 keV}=2.3 +/- 0.2 x 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.
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Cite
@article{arxiv.1006.5289,
title = {Discovery of VHE gamma-rays from the BL Lac object PKS 0548-322},
author = {H. E. S. S. collaboration and : and F. Aharonian and A. G. Akhperjanian and G. Anton and U. Barres de Almeida and A. R. Bazer-Bachi and Y. Becherini and B. Behera and W. Benbow and K. Bernlöhr and A. Bochow and C. Boisson and J. Bolmont and V. Borrel and J. Brucker and F. Brun and P. Brun and R. Bühler and T. Bulik and I. Büsching and T. Boutelier and P. M. Chadwick and A. Charbonnier and R. C. G. Chaves and A. Cheesebrough and L. -M. Chounet and A. C. Clapson and G. Coignet and M. Dalton and M. K. Daniel and I. D. Davids and B. Degrange and C. Deil and H. J. Dickinson and A. Djannati-Ataï and W. Domainko and L. O'C. Drury and F. Dubois and G. Dubus and J. Dyks and M. Dyrda and K. Egberts and D. Emmanoulopoulos and P. Espigat and C. Farnier and F. Feinstein and A. Fiasson and A. Förster and G. Fontaine and M. Füssling and S. Gabici and Y. A. Gallant and L. Gérard and D. Gerbig and B. Giebels and J. F. Glicenstein and B. Glück and P. Goret and D. Göring and D. Hauser and M. Hauser and S. Heinz and G. Heinzelmann and G. Henri and G. Hermann and J. A. Hinton and A. Hoffmann and W. Hofmann and M. Holleran and S. Hoppe and D. Horns and A. Jacholkowska and O. C. de Jager and C. Jahn and I. Jung and K. Katarzyński and U. Katz and S. Kaufmann and E. Kendziorra and M. Kerschhagg and D. Khangulyan and B. Khélifi and D. Keogh and W. Kluźniak and T. Kneiske and Nu. Komin and K. Kosack and G. Lamanna and J. -P. Lenain and T. Lohse and V. Marandon and J. M. Martin and O. Martineau-Huynh and A. Marcowith and J. Masbou and D. Maurin and T. J. L. McComb and M. C. Medina and R. Moderski and E. Moulin and M. Naumann-Godo and M. de Naurois and D. Nedbal and D. Nekrassov and B. Nicholas and J. Niemiec and S. J. Nolan and S. Ohm and J-F. Olive and E. de Oña Wilhelm and K. J. Orford and M. Ostrowski and M. Panter and M. Paz Arribas and G. Pedaletti and G. Pelletier and P. -O. Petrucci and S. Pita and G. Pühlhofer and M. Punch and A. Quirrenbach and B. C. Raubenheimer and M. Raue and S. M. Rayner and M. Renaud and F. Rieger and J. Ripken and L. Rob and S. Rosier-Lees and G. Rowell and B. Rudak and C. B. Rulten and J. Ruppel and V. Sahakian and A. Santangelo and R. Schlickeiser and F. M. Schöck and R. Schröder and U. Schwanke and S. Schwarzburg and S. Schwemmer and A. Shalchi and M. Sikora and J. L. Skilton and H. Sol and D. Spangler and L. Stawarz and R. Steenkamp and C. Stegmann and F. Stinzing and G. Superina and A. Szostek and P. H. Tam and J. -P. Tavernet and R. Terrier and O. Tibolla and M. Tluczykont and C. van Eldik and G. Vasileiadis and C. Venter and L. Venter and J. P. Vialle and P. Vincent and M. Vivier and H. J. Völk and F. Volp and S. J. Wagner and M. Ward and A. A. Zdziarski and A. Zech},
journal= {arXiv preprint arXiv:1006.5289},
year = {2015}
}
Comments
6 pages, 3 figures, Accepted for publication in Astronomy and Astrophysics