Agile Detection of Delayed Gamma-Ray Emission from the Short Gamma-Ray Burst GRB 090510
astro-ph.HE
/ Authors
A. Giuliani, F. Fuschino, G. Vianello, M. Marisaldi, S. Mereghetti, M. Tavani, S. Cutini, G. Barbiellini, F. Longo, E. Moretti
and 52 more authors
M. Feroci, E. Del Monte, A. Argan, A. Bulgarelli, P. Caraveo, P. W. Cattaneo, A. W. Chen, T. Contessi, F. D'Ammando, E. Costa, G. De Paris, G. Di Cocco, I. Donnarumma, Y. Evangelista, A. Ferrari, M. Fiorini, M. Galli, F. Gianotti, C. Labanti, I. Lapshov, F. Lazzarotto, P. Lipari, A. Morselli, L. Pacciani
/ Abstract
Short gamma-ray bursts (GRBs), typically lasting less than 2 s, are a special class of GRBs of great interest. We report the detection by the AGILE satellite of the short GRB 090510 which shows two clearly distinct emission phases: a prompt phase lasting ~ 200 msec and a second phase lasting tens of seconds. The prompt phase is relatively intense in the 0.3-10 MeV range with a spectrum characterized by a large peak/cutoff energy near 3 MeV, in this phase, no significant high-energy gamma-ray emission is detected. At the end of the prompt phase, intense gamma-ray emission above 30 MeV is detected showing a power-law time decay of the flux of the type t^-1.3 and a broad-band spectrum remarkably different from that of the prompt phase. It extends from sub-MeV to hundreds of MeV energies with a photon index alpha ~ 1.5. GRB 090510 provides the first case of a short GRB with delayed gamma-ray emission. We present the timing and spectral data of GRB 090510 and briefly discuss its remarkable properties within the current models of gamma-ray emission of short GRBs.