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Abdo, A.A; Ajello, M; Barbiellini, G; Bastieri, D; Bechtol, K; Berenji, B; Bonamente, E; Borgland, A.W; Burnett, T.H; Caliandro, G.A; Caraveo, P.A; Casandjian, J.M; Cecchi, C; Chiang, J; Ciprini, S; Cognard, I; Cominsky, L.R; Cutini, S; Dermer, C.D; de Angelis, A; do Couto e Silva, E; Dumora, D; Espinoza, C; Farnier, C; Favuzzi, C; Focke, W.B; Fortin, P; Fukazawa, Y; Funk, S; Gehrels, N; Giebels, B; Giglietto, N; Godfrey, G; Grenier, I.A; Grondin, M.-H; Grove, J.E; Guillemot, L; Guiriec, S; Hanabata, Y; Hayashida, M; Jackson, M.S; Jóhannesson, G; Johnson, A.S; Johnson, T.J; Johnson, W.N; Kamae, T; Katagiri, H; Kataoka, J; Katsuta, J; Kawai, N; Kerr, M; Knödlseder, J; Kramer, M; Longo, F; Loparco, F; Lott, B; Lovellette, M.N; Lubrano, P; Madejski, G.M; Mazziotta, M.N; Meurer, C; Monte, C; Monzani, M.E; Morselli, A; Moskalenko, I.V; Norris, J.P; Nuss, E; Ohsugi, T; Ormes, J.F; Parent, D; Pelassa, V; Pesce-Rollins, M; Piron, F; Razzano, M; Reimer, A; Reimer, O; Rochester, L.S; Romani, R.W; Ryde, F; Sadrozinski, H.F.-W; Sander, A; Sgrò, C; Siskind, E.J; Smith, D.A; Smith, P.D; Stappers, B.W; Stecker, F.W; Strickman, M.S; Suson, D.J; Tajima, H; Takahashi, H; Thayer, J.G; Tibolla, O; Torres, D.F; Tramacere, A; Venter, C; Vilchez, N; Wood, K.S; Yamazaki, R; Ylinen, T
Science (American Association for the Advancement of Science), 02/2010, Letnik: 327, Številka: 5969Journal Article
Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to approximately 10¹⁵ electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10⁸ electron volts and 3 x10¹¹ electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10⁹ electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.
