2010ApJ...722..543E -
Astrophys. J., 722, 543-549 (2010/October-2)
The high energy budget allocations in shocks and gamma ray bursts.
EICHLER D., GUETTA D. and POHL M.
Abstract (from CDS):
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, Fγ, 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 3-30 MeV energy range. The present-day energy input rate in γ-rays recorded by the GBM from long GRBs is found, assuming star formation rates in the literature, to be {dot}W(0)=0.5 F_γ H/c = 5 ×10^42 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 ∼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 γ-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 γ-ray beam. It is suggested that "orphan" neutrinos out of the γ-ray beam might be identifiable via orphan afterglow or other wide angle signatures of GRBs in lieu of coincidence with prompt γ-rays, and it is recommended that feasible single neutrino trigger criteria be established to search for such coincidences.
Abstract Copyright:
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Journal keyword(s):
astroparticle physics - cosmic rays - gamma-ray burst: general
Simbad objects:
14
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