Collaboration, H.E.S.S. and Abramowski, A. and Aharonian, F. and Ait Benkhali, F. and Akhperjanian, A.G. and Angüner, E. and Backes, M. and Balenderan, S. and Balzer, A. and Barnacka, A. and Becherini, Y. and Becker Tjus, J. and Berge, D. and Bernhard, S. and Bernlöhr, K. and Birsin, E. and Biteau, J. and Böttcher, M. and Boisson, C. and Bolmont, J. and Bordas, P. and Bregeon, J. and Brun, F. and Brun, P. and Bulik, T. and Carrigan, S. and Casanova, S. and Chadwick, P.M. and Chakraborty, M. and Chalme-Calvet, R. and Chaves, R.C.G. and Chrétien, M. and Colafrancesco, S. and Cologna, G. and Conrad, J. and Couturier, C. and Cui, Y. and Davids, I.D. and Degrange, B. and Deil, C. and deWilt, P. and Djannati-Ataï, A. and Domainko, W. and Donath, A. 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 Gabici, S. and Gajdus, M. and Gallant, Y.A. and Garrigoux, T. and Giavitto, G. and Giebels, B. and Glicenstein, J.F. and Gottschall, D. and Grondin, M.-H. and Grudzińska, M. and Hadasch, D. 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 Ivascenko, A. and Jacholkowska, A. and Jahn, C. and Jamrozy, M. and Janiak, M. and Jankowsky, F. and Jung-Richardt, 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 Lefranc, V. 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 Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Morå, K. 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 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 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 Reichardt, I. and Reimer, A. and Reimer, O. and Renaud, M. and Reyes, R. de los and Rieger, F. and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C.B. and Sahakian, V. and Salek, D. 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 Spanier, F. 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 Veh, J. 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 Weitzel, Q. and White, R. and Wierzcholska, A. and Willmann, P. and Wörnlein, A. and Wouters, D. and Yang, R. and Zabalza, V. and Zaborov, D. and Zacharias, M. and Zajczyk, A. and Zdziarski, A.A. and Zech, A. and Zechlin, H.-S. (2015) 'H.E.S.S. reveals a lack of TeV emission from the supernova remnant Puppis A.', Astronomy & astrophysics., 575 . A81.
Context. Puppis A is an interesting ~4 kyr-old supernova remnant (SNR) that shows strong evidence of interaction between the forward shock and a molecular cloud. It has been studied in detail from radio frequencies to high-energy (HE, 0.1−100 GeV) γ-rays. An analysis of the Fermi-LAT data has shown extended HE γ-ray emission with a 0.2−100 GeV spectrum exhibiting no significant deviation from a power law, unlike most of the GeV-emitting SNRs known to be interacting with molecular clouds. This makes it a promising target for imaging atmospheric Cherenkov telescopes (IACTs) to probe the γ-ray emission above 100 GeV. Aims. Very-high-energy (VHE, E ≥ 0.1 TeV) γ-ray emission from Puppis A has been, for the first time, searched for with the High Energy Stereoscopic System (H.E.S.S.). Methods. Stereoscopic imaging of Cherenkov radiation from extensive air showers is used to reconstruct the direction and energy of the incident γ-rays in order to produce sky images and source spectra. The profile likelihood method is applied to find constraints on the existence of a potential break or cutoff in the photon spectrum. Results. The analysis of the H.E.S.S. data does not reveal any significant emission towards Puppis A. The derived upper limits on the differential photon flux imply that its broadband γ-ray spectrum must exhibit a spectral break or cutoff. By combining Fermi-LAT and H.E.S.S. measurements, the 99% confidence-level upper limits on such a cutoff are found to be 450 and 280 GeV, assuming a power law with a simple exponential and a sub-exponential cutoff, respectively. It is concluded that none of the standard limitations (age, size, radiative losses) on the particle acceleration mechanism, assumed to be continuing at present, can explain the lack of VHE signal. The scenario in which particle acceleration has ceased some time ago is considered as an alternative explanation. The HE/VHE spectrum of Puppis A could then exhibit a break of non-radiative origin (as observed in several other interacting SNRs, albeit at somewhat higher energies), owing to the interaction with dense and neutral material, in particular towards the NE region.
|Keywords:||Gamma rays: ISM, ISM: individual objects: Puppis A, Radiation mechanisms: non-thermal, Cosmic rays, Acceleration of particles.|
|Full text:||(VoR) Version of Record|
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|Publisher Web site:||http://dx.doi.org/10.1051/0004-6361/201424805|
|Publisher statement:||Reproduced with permission from Astronomy & Astrophysics, © ESO, 2015.|
|Date accepted:||20 December 2014|
|Date deposited:||22 April 2015|
|Date of first online publication:||March 2015|
|Date first made open access:||No date available|
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