On the Neutrino Flux from Gamma-Ray Bursts

Abstract

Observations imply that gamma-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a highly relativistic fireball. Photo-meson interactions of protons with gamma-rays within the fireball dissipation region are expected to convert a significant fraction of fireball energy to >10^14 eV neutrinos. We present an analysis of the internal shock model of GRBs, where production of synchrotron photons and photo-meson neutrinos are self-consistently calculated, and show that the fraction of fireball energy converted to high energy neutrinos is not sensitive to uncertainties in fireball model parameters, such as the expansion Lorentz factor and characteristic variability time. This is due in part to the constraints imposed on fireball parameters by observed GRB characteristics, and in part to the fact that for parameter values for which the photo-meson optical depth is high (implying high proton energy loss to pion production) neutrino production is suppressed by pion and muon synchrotron losses. The neutrino flux is therefore expected to be correlated mainly with the observed gamma-ray flux. The time averaged neutrino intensity predicted by the model, ~10^-8.5 GeV/cm^2 s sr, is consistent with the flux predicted by the assumption that GRBs are the sources of >10^19 eV cosmic-rays.