Neutrino Oscillations Within the Induced Gravitational Collapse Paradigm of Long Gamma-Ray Bursts

The induced gravitational collapse (IGC) paradigm of long gamma-ray bursts (GRBs) associated with supernovae (SNe) predicts a copious neutrino-antineutrino ($\nu\bar{\nu}$) emission owing to the hypercritical accretion process of SN ejecta onto a neutron star (NS) binary companion. The neutrino emission can reach luminosities of up to $10^{57}$MeV s$^{-1}$, mean neutrino energies 20 MeV, and neutrino densities $10^{31}$ cm$^{-3}$. Along their path from the vicinity of the NS surface outward, such neutrinos experience flavor transformations dictated by the neutrino to electron density ratio. We determine the neutrino and electron on the accretion zone and use them to compute the neutrino flavor evolution. For normal and inverted neutrino-mass hierarchies and within the two-flavor formalism ($\nu_{e}\nu_{x}$), we estimate the final electronic and non-electronic neutrino content after two oscillation processes: (1) neutrino collective effects due to neutrino self-interactions where the neutrino density dominates and, (2) the Mikheyev-Smirnov-Wolfenstein (MSW) effect, where the electron density dominates. We find that the final neutrino content is composed by $\sim$55% ($\sim$62%) of electronic neutrinos, i.e. $\nu_{e}+\bar{\nu}_{e}$, for the normal (inverted) neutrino-mass hierarchy. The results of this work are the first step toward the characterization of a novel source of astrophysical MeV-neutrinos in addition to core-collapse SNe and, as such, deserve further attention.