TY  - JOUR
A1  - Lange, J.
A1  - Pohl, Martin
T1  - The average GeV-band emission from gamma-ray bursts
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We analyze the emission in the 0.3-30 GeV energy range of gamma-ray bursts detected with the Fermi Gamma-ray Space Telescope. We concentrate on bursts that were previously only detected with the Gamma-Ray Burst Monitor in the keV energy range. These bursts will then be compared to the bursts that were individually detected with the Large Area Telescope at higher energies.
 Methods. To estimate the emission of faint GRBs we used nonstandard analysis methods and sum over many GRBs to find an average signal that is significantly above background level. We used a subsample of 99 GRBs listed in the Burst Catalog from the first two years of observation.
 Results. Although most are not individually detectable, the bursts not detected by the Large Area Telescope on average emit a significant flux in the energy range from 0.3 GeV to 30 GeV, but their cumulative energy fluence is only 8% of that of all GRBs. Likewise, the GeV-to-MeV flux ratio is less and the GeV-band spectra are softer. We confirm that the GeV-band emission lasts much longer than the emission found in the keV energy range. The average allsky energy flux from GRBs in the GeV band is 6.4 x 10(-4) erg cm(-2) yr(-1) or only similar to 4% of the energy flux of cosmic rays above the ankle at 10(18.6) eV.
KW  - methods: statistical
KW  - surveys
KW  - gamma-ray burst: general
Y1  - 2013
U6  - https://doi.org/10.1051/0004-6361/201220652
SN  - 0004-6361
VL  - 551
IS  - 1
PB  - EDP Sciences
CY  - Les Ulis
ER  -