Neutrino Oscillation Effects on the Luminosity of Neutrino-dominated Accretion Flows around Black Holes

Abstract

A stellar-mass black hole surrounded by the neutrino-dominated accretion flow (NDAF) has been proposed as the central engine of gamma-ray bursts. In this work, we investigate the neutrino/antineutrino luminosity and annihilation luminosity from the NDAF and pair annihilation model, taking into account the neutrino oscillation above the accretion disk. The disk's hydrodynamical properties are modeled using an empirical solution previously derived with boundary conditions, including the effect of electron degeneracy and neutrino trapping. Our key parameters are the mass accretion rate and the black hole spin given in the ranges of $\dot{M}=0.1$ –10 M _⊙ s ^−1 and 0 ≤ a < 1, respectively. Without neutrino oscillation, the obtained neutrino/antineutrino luminosity is ∼10 ^51 –10 ^53 erg s ^−1 , while the neutrino annihilation luminosity is found to be ∼10 ^46 –10 ^51 erg s ^−1 . In the presence of neutrino oscillation in the vacuum limit, the electron neutrino annihilation luminosity decreases by ≲22% through the flavor transformation, while the muon and tau neutrino luminosity can increase by up to ∼45% and 60%, respectively. As a result, the total annihilation luminosity can be reduced by up to ∼19% due to the oscillation process above the disk. Finally, we also investigate the case whereby the charge-conjugation-parity-symmetry-violating (CP-violating) phase is changed from δ CP = 0° to 245°. However, our results reveal that the CP-violating phase has minimal impact on the neutrino annihilation luminosity.

Keywords

• Accretion
• Black hole physics
• Neutrino oscillations