Neutrino emission from high-energy component gamma-ray bursts

Abstract

Gamma-ray bursts have the potential to produce the particle energies (up to $10^{21}$ eV) and the energy budget ($10^{44} \rm{erg yr^{-1} Mpc^{-3}}$) to accommodate the spectrum of the highest energy cosmic rays; on the other hand, there is no observational evidence yet that they accelerate hadrons. Fermi recently observed two bursts that exhibit a power-law high-energy extension of the typical (Band) spectrum that extends to $\sim 30$ GeV. On the basis of fireball phenomenology we argue that they, along with GRB941017 observed by EGRET in 1994, show indirect evidence for considerable baryon loading. Since the detection of neutrinos is the only unambiguous way to establish that GRBs accelerate cosmic rays, we use two methods to estimate the neutrino flux produced when the baryons interact with fireball photons to produce charged pions and neutrinos. While the number of events expected from the Fermi bursts is small, we conclude that an event like GRB941017 will be detected by IceCube if gamma-ray bursts are indeed the sources of the cosmic rays.