Journal
ASTROPHYSICAL JOURNAL
Volume 722, Issue 1, Pages 543-549Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/722/1/543
Keywords
astroparticle physics; cosmic rays; gamma-ray burst: general
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Funding
- Israel-US Binational Science Foundation
- Israeli Academy of Science
- Joan and Robert Arnow Chair of Theoretical Astrophysics
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The statistical distribution of energies among particles responsible for long gamma-ray burst (GRB) emission is analyzed in light of recent results of the Fermi Observatory. The all-sky flux, F., recorded by the Gamma-Ray Burst Monitor (GBM) is shown, despite its larger energy range, to be not significantly larger than that reported by the Burst and Transient Explorer, suggesting a relatively small flux in the 3-30MeV energy range. The present-day energy input rate in gamma-rays recorded by the GBM from long GRBs is found, assuming star formation rates in the literature, to be W(0) = 0.5F gamma H/c = 5x10(42) erg Mpc(-3) yr(-1). The Large Area Telescope fluence, when observed, is about 5%-10% per decade of the total, in good agreement with the predictions of saturated, nonlinear shock acceleration. The high-energy component of long GRBs, as measured by Fermi, is found to contain only similar to 10-2.5 of the energy needed to produce ultrahigh-energy cosmic rays (UHECRs) above 4 EeV, assuming the latter to be extragalactic, when various numerical factors are carefully included, if the cosmic-ray source spectrum has a spectral index of -2. The observed. -ray fraction of the required UHECR energy is even smaller if the source spectrum is softer than E-2. The AMANDA II limits rule out such a GRB origin for UHECRs if much more than 10(-2) of the cosmic-ray energy goes into neutrinos that are within, and simultaneous with, the gamma-ray beam. It is suggested that orphan neutrinos out of the gamma-ray beam might be identifiable via orphan afterglow or other wide angle signatures of GRBs in lieu of coincidence with prompt gamma-rays, and it is recommended that feasible single neutrino trigger criteria be established to search for such coincidences.
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