Neutrino emission in the jet propagation process

Abstract

Relativistic jets are universal in long-duration gamma-ray burst (GRB) models. Before breaking out, they must propagate in the progenitor envelope along with a forward shock and a reverse shock forming at the jet head. Both electrons and protons will be accelerated by the shocks. High-energy neutrinos could be produced by these protons interacting with stellar materials and electron-radiating photons. The jet will probably be collimated, which may have a strong effect on the final neutrino flux. Under the assumption of a power-law stellar-envelope density profile ρr -α with index α, we calculate the neutrino emission flux by these shocks for low-luminosity GRBs (LL-GRBs) and ultra-long GRBs (UL-GRBs) in different collimation regimes, using the jet propagation framework developed by Bromberg et al. We find that LL-GRBs and UL-GRBs are capable of producing detectable high-energy neutrinos up to PeV, from which the final neutrino spectrum can be obtained. Further, we conclude that a larger α corresponds to greater neutrino flux at the high-energy end (PeV) and to higher maximum neutrino energy as well. However, such differences are so small that it is not promising for us to be able to distinguish these in observations, given the energy resolution we have now. © 2014. The American Astronomical Society. All rights reserved..