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Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)
A. Abdo A., Ackermann M., Ajello M., Allafort A., Baldini L. et al
Astrophysical Journal 718 (2010) 348-356 - http://hal.in2p3.fr/in2p3-00529638
Physique/Astrophysique/Phénomènes cosmiques de haute energie
Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)
A. A. Abdo, M. Ackermann, M. Ajello, A. Allafort, L. Baldini, J. Ballet1, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, A. Bouvier, T. J. Brandt2, J. Bregeon, M. Brigida, P. Bruel3, R. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, S. Carrigan, J. M. Casandjian1, C. Cecchi, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi4, J. Conrad, C. D. Dermer, F. De Palma, E. Do Couto E Silva, P. S. Drell, R. Dubois, D. Dumora5, C. Farnier4, C. Favuzzi, S. J. Fegan3, Y. Fukazawa, Y. Fukui, S. Funk, P. Fusco, F. Gargano, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, T. Glanzman, G. Godfrey, I. A. Grenier1, J. E. Grove, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, E. Hays, D. Horan3, R. E. Hughes, G. Johannesson, A. S. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, J. Kataoka, J. Knodlseder2, M. Kuss, J. Lande, L. Latronico, S.-H. Lee, M. Lemoine-Goumard5, M. Llena Garde, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, A. Makeev, M. N. Mazziotta, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, P. L. Nolan, J. P. Norris, E. Nuss4, M. Ohno, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, J. H. Panetta, D. Parent5, V. Pelassa4, M. Pepe, M. Pesce-Rollins, F. Piron4, T. A. Porter, S. Raino, R. Rando, M. Razzano, A. Reimer, O. Reimer, T. Reposeur5, A. Y. Rodriguez, M. Roth, H. F.-W. Sadrozinski, A. Sander, P. M. Saz Parkinson, C. Sgro, E. J. Siskind, D. A. Smith5, P. D. Smith, G. Spandre, P. Spinelli, M. S. Strickman, D. J. Suson, H. Tajima, H. Takahashi, T. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, L. Tibaldo1, O. Tibolla, D. F. Torres, G. Tosti, Y. Uchiyama, T. Uehara, T. L. Usher, V. Vasileiou, N. Vilchez2, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, H. Yamamoto, R. Yamazaki, Z. Yang, T. Ylinen, M. Ziegler
1 :  AIM - UMR 7158 - Astrophysique Interactions Multi-échelles
http://irfu.cea.fr/Sap/
CNRS : UMR7158 – INSU – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
AIM - UMR 7158, Service d'astrophysique, CEA/Saclay, Orme des Merisiers F-91191 GIF SUR YVETTE CEDEX
France
2 :  CESR - Centre d'étude spatiale des rayonnements
http://www.cesr.fr
CNRS : UMR5187 – Observatoire Midi-Pyrénées – INSU – Université Paul Sabatier (UPS) - Toulouse III
9 Av du colonel Roche - BP 4346 31028 TOULOUSE CEDEX 4
France
3 :  LLR - Laboratoire Leprince-Ringuet
http://polywww.in2p3.fr/
CNRS : UMR7638 – IN2P3 – Polytechnique - X
Route de Saclay - 91128 Palaiseau Cedex
France
4 :  LPTA - Laboratoire de Physique Théorique et Astroparticules
http://www.lpta.in2p3.fr/
CNRS : UMR5207 – IN2P3 – Université Montpellier II - Sciences et techniques
Bât 13- 1er Et. - CC 070 Place Eugène Bataillon 34095 MONTPELLIER CEDEX 5
France
5 :  CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
http://www.cenbg.in2p3.fr/
CNRS : UMR5797 – IN2P3 – Université Sciences et Technologies - Bordeaux I
Chemin du Solarium - BP 120 - 33175 Gradignan Cedex
France
We present detailed analysis of the two gamma-ray sources,1FGL J1801.3-2322c and 1FGL J1800.5-2359c,that have been found toward the supernova remnant(SNR) W28 with the Large Area Telescope(LAT) on board the Fermi Gamma-ray Space Telescope.1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28,and to extensively overlap with the TeV gamma-ray source HESS J1801-233,which is associated with a dense molecular cloud interacting with the supernova remnant.The gamma-ray spectrum measured with LAT from 0.2--100 GeV can be described by a broken power-law function with a break of ~1GeV,and photon indices of 2.09$\pm$0.08(stat)$\pm$0.28(sys) below the break and 2.74$\pm$0.06(stat)$\pm$0.09(sys) above the break.Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV--TeV band,we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud.The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provide a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved.An upper limit on the size of the gamma-ray emission was estimated to be ~16$'$ using events above ~2GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B,which is considered to be associated with a dense molecular cloud that contains the ultra compact HII region W28A2(G5.89-0.39).We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C.The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10GeV and 100GeV.
Fermi-LAT

Articles dans des revues avec comité de lecture
20/07/2010
Astrophysical Journal (Astrophys. J.)
Publisher American Astronomical Society
ISSN 0004-637X 
718
348-356

98.58.Mj Supernova remnants 98.58.Db Molecular clouds, H2 clouds, dense clouds, and dark clouds 95.30.Ky Atomic and molecular data, spectra, and spectral parameters (opacities, rotation constants, line identification, oscillator strengths, g
23 pages, 6 figures. Accepted for publication in the Astrophysical Journal. Corresponding authors: H. Katagiri, H. Tajima, T. Tanaka, and Y. Uchiyama
Lien vers le texte intégral : 
http://fr.arXiv.org/abs/1005.4474