Effects of Modified Theories of Gravity on Neutrino Pair Annihilation Energy Deposition near Neutron Stars

Abstract

We study the neutrino pair annihilation into electron–positron pairs ( ) near the surface of a neutron star. The analysis is performed in the framework of extended theories of gravity. The latter induce a modification of the minimum photon sphere radius (R ph) and the maximum energy deposition rate near R ph, as compared to those of general relativity. These results might lead to an efficient mechanism for generating GRBs.

Neutrino pair annihilation ($$\nu {\bar{\nu }}\rightarrow e^-e^+$$) in the presence of quintessence surrounding a black hole

“…In this section we recall the main features to treat the energy deposition in curved spacetimes [82,96]. As mentioned in the Introduction, previous calculations of the ν ν → e − e + reaction in the vicinity of a neutron star have been first based on Newtonian gravity [76,77], then the effect of gravity has been incorporated for static stars [75,79], and then extended to rotating stars [82,92].…”

“…Following the procedure of Ref. [75], one finds that the above expressions, written in terms of the metric component g 00 = g −1 rr = f (r ), are given by (see for example [96])…”

“…It is worth to mention that the neutrino pair annihilation rate into electron pairs between two neutron stars in a binary system has been investigated in [79], while the study of the structure of neutron star disks based on the two-region (inner and outer) disk scenario has been performed in [90], where the neutrino annihilation luminosity from the disk has been calculated in various cases (see also [91][92][93][94][95]). The neutrinoantineutrino annihilation into electron-positron pairs near the surface of a neutron star assuming that the gravitational background is described by modified theories of gravity has been investigated in [96].…”

“…Motivated by the fact that gravity may influence energy deposition rate near to the photon-sphere, R ph , as compared to one derived in the framework of Newtonian gravity [75], we extend this analysis to the case of black hole spacetimes modified by quintessence fields. In particular, we focus on the process ν ν → e + e − , which is important also for the delay shock mechanism into the Type II Supernova: indeed, at late time, from the hot proto-neutron star, the energy is deposited into the supernova envelope via neutrino pair annihilation and neutrino-lepton scattering [96]. As we shall see, the computation of the efficiency of the process ν ν → e + e − may increase by more than one order of magnitude respect to GR, making possible to explain the huge energy of the GRB energy emitted in the merging of a binary neutron star system, considering the neutrino annihilation as the unique source.…”

Photon frequency shift in curvature-based Extended Theories of Gravity

“…In particular, some models of ETG have been studied in the Newtonian limit [18,19], as well as in the Minkowskian limit [20][21][22][23][24][25][26]. The weak-field limit has to be tested against realistic self-gravitating systems.…”