Details

Autor(en) / Beteiligte

• Axelsson, M
• Baldini, L
• Barbiellini, G
• Baring, M G
• Bellazzini, R
• BREGEON, J
• Brigida, M
• Bruel, P
• Buehler, R
• Caliandro, G A

Titel

GRB110721A: AN EXTREME PEAK ENERGY AND SIGNATURES OF THE PHOTOSPHERE

Ist Teil von

• Astrophysical journal. Letters, 2012-10, Vol.757 (2), p.1-6

Ort / Verlag

United States: Bristol : IOP Publishing

Erscheinungsjahr

2012

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 s (in the GBM) and had a peak flux of (5.7 + or - 0.2) x 10 super(?5) erg s super(?1) cm super(?2). The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 + or - 2 MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of -1.89 + or - 0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.