MeV–GeV neutrino propagation as a signal of magnetic field amplification in neutron star merger

Abstract

Short gamma-ray bursts (sGRBs) have widely been accepted to arise from a compact object binary merger; neutron star–neutron star or neutron star–black hole. During the merger of a binary neutron star system, magnetic field can be amplified beyond magnetar field strength (∼1015–1016 G) by Kelvin–Helmholtz instabilities. Considering this effect on the GRB “fireball” dynamics, we study the emission, propagation and oscillation of multi MeV–GeV neutrinos through their self-energies and using these we compute the neutrino effective potential up to order MW−4. Additionally, we calculate the number of neutrino events and neutrino flavor ratios that we would expect on Hyper-Kamiokande and DeepCore experiments. We found that MeV neutrinos in a strong magnetic field could provide information of the topology of the field, and that the number of GeV neutrinos expected in DeepCore detector would be directly affected by the strength of the field. It is worth noting that our estimates correspond to the only trustworthy method for verifying the effect of the magnetic field amplification.