Neutrino heating near hyper-accreting black holes

Abstract

Hyper-accretion discs around black holes emit copious neutrinos and anti-neutrinos. A fraction of the emitted neutrinos convert to electron-positron plasma above the disc through the annihilation reaction $\nu\bar\nu\to e^+e^-$. This process may drive relativistic jets associated with GRB explosions. We calculate the efficiency of energy deposition by neutrinos. Our calculation is fully relativistic and based on a geodesic-tracing method. We find that the efficiency of neutrino heating is a well-defined function of (i) accretion rate and (ii) spin of the black hole. It is practically independent of the details of neutrino transport in the opaque zone of the disc. The results help identify accretion discs whose neutrino emission can power GRBs.Comment: 8 pages, 8 figures, accepted for publication in MNRA

Neutrino Spectra From Accretion Disks: Neutrino General Relativistic Effects and the Consequences for Nucleosynthesis

“…It is interesting to contrast our results with Zalamea &Belobodorov (2011) andBirkl et al (2007). These authors found that the neutrino-antineutrino annihilation rate above the disk was greatly enhanced by the inclusion of general relativistic effects while we find that the influence of neutrinos on nucleosynthetic outcomes is decreased when general relativistic effects on emitted neutrinos are considered.…”

“…Null geodesics for neutrinos emitted from accretion disks have been studied for the purposes of determining neutrino and antineutrino annihilation rates that may be relevant as an energy deposition mechanism for gamma ray bursts, e.g., Zalamea &Belobodorov (2011) andBirkl et al (2007). The typical method is to follow the null geodesics starting from the observer and ending at the neutrino surface.…”

“…A more recent work compared different models for the accretion disk and applied their results to ultraluminous X-ray sources (Lorenzin & Zampieri 2009). To date, studies of the effects of general relativity, including ray bending, on neutrinos emerging from accretion disks have focused on neutrino pair annihilation rates and their production of gamma ray bursts (Asano & Fukuyama 2001;Birkl et al 2007;Zalamea & Belobodorov 2011).…”

Gravitational-Wave Observations May Constrain Gamma-Ray Burst Models: The Case of Gw150914–gbm

“…This corresponds to E=62 f r (0.67) M ☉ c 2 ≈6.7×10 54 erg, which is four orders of magnitude more than the observed energy release. Methods of tapping energy from the merged BH include neutrino-driven disks (Zalamea & Beloborodov 2011) and the Blandford-Znajek (BZ) process (Blandford & Znajek 1977;see however Lyutikov 2016).…”

Radiative decay of keV-mass sterile neutrino in magnetized electron plasma

“…In astrophysics, "magnetars" are usually identified with objects like Soft Gamma-ray Repeaters (SGR) and Anomalous X-ray Pulsars (AXP) [4]. Recent simulations of core-collapse supernovae [5][6][7] and the formation of accretion discs at the merger of compact objects in a close binary system [8,9] demonstrate that the magnetic field strength could reach the value of B ∼ 10 15 Gauss.…”