Neutrinos from gamma-ray bursts: propagation of cosmic rays in their host galaxies

TL;DR

This study investigates whether gamma-ray burst host galaxies can produce the PeV neutrinos observed by IceCube through cosmic ray interactions, finding the predicted flux is lower than observed but not conclusively ruled out.

Contribution

It introduces a method to estimate neutrino production efficiency from GRB host galaxy properties and calculates the expected neutrino flux based on current data.

Findings

Estimated neutrino flux is about 0.3×10^{-8} GeV cm^{-2} s^{-1} sr^{-1} per flavor.

The predicted flux is insufficient to explain IceCube observations.

Uncertainties in assumptions prevent ruling out GRBs as neutrino sources.

Abstract

Gamma-ray bursts (GRBs) are proposed as candidate sources of ultra-high energy cosmic rays (UHECRs). We study the possibility that the PeV neutrinos recently observed by IceCube are produced by GRB cosmic rays interacting with the interstellar gas in the host galaxies. By studying the relation between the X-ray absorption column density N_H and the surface star-formation rate of GRB host galaxies, we find that N_H is a good indicator of the surface gas density of the host galaxies. Then we are able to calculate the neutrino production efficiency of CRs for GRBs with known N_H. We collect a sample of GRBs that have both measurements of N_H and accurate gamma-ray fluence, and attempt to calculate the accumulated neutrino flux based on the current knowledge about GRBs and their host galaxies. When the CR intensity produced by GRBs is normalized with the observed UHECR flux above $10^{19}{\rm eV}$, the accumulated neutrino flux at PeV energies is estimated to be about $(0.3\pm0.2)\times10^{-8} \rm{GeV\ cm^{-2}\ s^{-1}\ sr^{-1}} $ (per flavor) under the assumption that GRB energy production rate follows the cosmic star-formation rate and the favorable assumption about the CR diffusion coefficient. This flux is insufficient to account for the IceCube observations, but the estimate suffers from some assumptions in the calculation and thus we can not rule out this scenario at present.