Diffuse PeV neutrinos from gamma-ray bursts

TL;DR

This paper investigates whether gamma-ray bursts, including untriggered and low-luminosity ones, can produce the PeV neutrinos detected by IceCube, finding that they likely cannot fully account for the observed events.

Contribution

It models the neutrino production from both triggered and untriggered GRBs using Monte Carlo simulations, providing new insights into their combined contribution to PeV neutrinos.

Findings

Untriggered GRBs produce about twice the neutrino flux of triggered ones.

The total GRB neutrino flux is insufficient to explain IceCube's PeV neutrinos.

Low-luminosity and early GRBs may contribute but are unlikely to be the main sources.

Abstract

The IceCube collaboration recently reported the potential detection of two cascade neutrino events in the energy range 1-10 PeV. We study the possibility that these PeV neutrinos are produced by gamma-ray bursts (GRBs), paying special attention to the contribution by untriggered GRBs that elude detection due to their low photon flux. Based on the luminosity function, rate distribution with redshift and spectral properties of GRBs, we generate, using Monte-Carlo simulation, a GRB sample that reproduce the observed fluence distribution of Fermi/GBM GRBs and an accompanying sample of untriggered GRBs simultaneously. The neutrino flux of every individual GRBs is calculated in the standard internal shock scenario, so that the accumulative flux of the whole samples can be obtained. We find that the neutrino flux in PeV energies produced by untriggered GRBs is about 2 times higher than that produced by the triggered ones. Considering the existing IceCube limit on the neutrino flux of triggered GRBs, we find that the total flux of triggered and untriggered GRBs can reach at most a level of ~10^-9 GeV cm^-2 s^-1 sr^-1, which is insufficient to account for the reported two PeV neutrinos. Possible contributions to diffuse neutrinos by low-luminosity GRBs and the earliest population of GRBs are also discussed.