Fermi-LAT Study of Gamma-ray Emission in the Direction of Supernova Remnant W49B

A.A. Abdo , Markus Ackermann , Marco Ajello , Luca Baldini , Jean Ballet (1) , Guido Barbiellini , D. Bastieri , K. Bechtol , R. Bellazzini , E. D. Bloom , E. Bonamente , A. W. Borgland , A. Bouvier , J. Bregeon , A. Brez , M. Brigida , Pascal Bruel (2) , R. Buehler , S. Buson , G. A. Caliandro , R. A. Cameron , P. A. Caraveo , J. M. Casandjian (1) , C. Cecchi , Ö. Çelik , C. C. Cheung , J. Chiang , S. Ciprini , R. Claus , J. Cohen-Tanugi (3) , J. Conrad , C. D. Dermer , F. de Palma , S. W. Digel , E. Do Couto E Silva , P. S. Drell , D. Dumora (4) , C. Favuzzi , S. Funk , P. Fusco , F. Gargano , N. Gehrels , N. Giglietto , F. Giordano , M. Giroletti , T. Glanzman , G. Godfrey , I. A. Grenier (1) , M.-H. Grondin (4) , J. E. Grove , L. Guillemot (4) , S. Guiriec , D. Hadasch , Y. Hanabata , A. K. Harding , M. Hayashida , E. Hays , D. Horan (2) , R. E. Hughes , M. S. Jackson , G. Jóhannesson , A. S. Johnson , W. N. Johnson , T. Kamae , H. Katagiri , J. Kataoka , J. Katsuta , Jürgen Knödlseder (5) , M. Kuss , J. Lande , L. Latronico , S.-H. Lee , M. Lemoine-Goumard (4) , F. Longo , F. Loparco , M. N. Lovellette , P. Lubrano , A. Makeev , M. N. Mazziotta , T. Mizuno , C. Monte , M. E. Monzani , A. Morselli , I. V. Moskalenko , S. Murgia , M. Naumann-Godo (1) , P. L. Nolan , J. P. Norris , E. Nuss (3) , T. Ohsugi , A. Okumura , N. Omodei , E. Orlando , J. F. Ormes , V. Pelassa (3) , M. Pepe , M. Pesce-Rollins , F. Piron (3) , S. Rainò , R. Rando , M. Razzano , A. Reimer , O. Reimer , T. Reposeur (4) , J. Ripken , M. Roth , H. F.-W. Sadrozinski , A. Sander , P. M. Saz Parkinson , C. Sgrò , E. J. Siskind , David Stanley Smith (4) , P. D. Smith , P. Spinelli , M. S. Strickman , D. J. Suson , H. Tajima , H. Takahashi , T. Takahashi , T. Tanaka , L. Tibaldo (1) , O. Tibolla , D. F. Torres , G. Tosti , A. Tramacere , Y. Uchiyama , T. L. Usher , J. Vandenbroucke , V. Vasileiou , V. Vitale , A. P. Waite , P. Wang , B. L. Winer , K. S. Wood , T. Ylinen , M. Ziegler

1 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
2 LLR - Laboratoire Leprince-Ringuet
3 LPTA - Laboratoire de Physique Théorique et Astroparticules
4 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
5 CESR - Centre d'étude spatiale des rayonnements

We present an analysis of the gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the direction of SNR W49B (G43.3-0.2). A bright unresolved gamma-ray source detected at a significance of 38 sigma is found to coincide with SNR W49B. The energy spectrum in the 0.2-200 GeV range gradually steepens toward high energies. The luminosity is estimated to be 1.5x10^{36} (D/8 kpc)^2 erg s^-1 in this energy range. There is no indication that the gamma-ray emission comes from a pulsar. Assuming that the SNR shell is the site of gamma-ray production, the observed spectrum can be explained either by the decay of neutral pi mesons produced through the proton-proton collisions or by electron bremsstrahlung. The calculated energy density of relativistic particles responsible for the LAT flux is estimated to be remarkably large, U_{e,p}>10^4 eV cm^-3, for either gamma-ray production mechanism.

Mots clés: acceleration of particles; ISM: individual objects (W49B); radiation mechanisms: non-thermal

Domaines: Phénomènes cosmiques de haute energie [astro-ph.HE]; Phénomènes cosmiques de haute energie [astro-ph.HE]

A.A. Abdo, Markus Ackermann, Marco Ajello, Luca Baldini, Jean Ballet, et al.. Fermi-LAT Study of Gamma-ray Emission in the Direction of Supernova Remnant W49B. The Astrophysical Journal, 2010, 722, pp.1303-1311. ⟨10.1088/0004-637X/722/2/1303⟩. ⟨in2p3-00584255⟩