AGILE DETECTION OF DELAYED GAMMA-RAY EMISSION FROM THE SHORT GAMMA-RAY BURST GRB 090510
Giuliani, A. ; Fuschino, F. ; Vianello, G. ; Giommi, P. ; Colafrancesco, S. ; Salotti, L.
Jan - 2010
DOI: 10.1088/2041-8205/708/2/L84
ISSN : 2041-8205 ;
journal : The Astrophysical Journal

Volume : 708 ; Issue : 2
type: Article Journal

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 ms 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 broadband spectrum remarkably different from that of the prompt phase. It extends from sub-MeV to hundreds of MeV energies with a photon index ± C 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.

keywords : gamma rays: bursts