High-resolution calculations of merging neutron stars - II. Neutrino emission

Abstract

The remnant resulting from the merger of two neutron stars produces neutrinos\nin copious amounts. In this paper we present the neutrino emission results\nobtained via Newtonian, high-resolution simulations of the coalescence event.\nThese simulations use three-dimensional smoothed particle hydrodynamics\ntogether with a nuclear, temperature dependent equation of state and a\nmulti-flavour neutrino leakage scheme. We present the details of our scheme,\ndiscuss the neutrino emission results from a neutron star coalescence and\ncompare them to the core-collapse supernova case where neutrino emission has\nbeen studied for several decades. The average neutrino energies are similar to\nthose in the supernova case, but contrary to the latter, the luminosities are\ndominated by electron-type antineutrinos which are produced in the hot,\nneutron-rich, thick disk of the merger remnant. The cooler parts of this disk\ncontain substantial fractions of heavy nuclei, which, however, do not influence\nthe overall neutrino emission results significantly. Our total neutrino\nluminosities from the merger event are considerably lower than those found in\nprevious investigations. This has serious consequences for the ability to\nproduce a gamma-ray burst via neutrino annihilation. The neutrinos are emitted\npreferentially along the initial binary rotation axis, an event seen\n``pole-on'' would appear much brighter in neutrinos than a similar event seen\n``edge-on''.\n