Colliding neutron stars --- Gravitational waves, neutrino emission, and gamma-ray bursts

TL;DR

This paper presents detailed simulations of neutron star collisions, analyzing gravitational waves, neutrino emissions, and gamma-ray burst implications, concluding that neutrino-powered gamma-ray bursts are unlikely due to baryon pollution.

Contribution

It introduces a Newtonian hydrodynamical simulation including gravitational wave emission and neutrino physics for neutron star collisions, providing new insights into their electromagnetic and gravitational signals.

Findings

Neutrino luminosity peaks at over 4E54 erg/s for milliseconds.

Neutrino annihilation efficiency is about 1%, depositing ~1E50 erg.

Baryon pollution prevents formation of relativistic fireballs for gamma-ray bursts.

Abstract

Three-dimensional hydrodynamical simulations are presented for the direct head-on or off-center collision of two neutron stars, employing a basically Newtonian PPM code but including the emission of gravitational waves and their back-reaction on the hydrodynamical flow. A physical nuclear equation of state is used that allows us to follow the thermodynamical evolution of the stellar matter and to compute the emission of neutrinos. Predicted gravitational wave signals, luminosities and waveforms, are presented. The models are evaluated for their implications for gamma-ray burst scenarios. We find an extremely luminous outburst of neutrinos with a peak luminosity of more than 4E54 erg/s for several milliseconds. This leads to an efficiency of about 1% for the annihilation of neutrinos with antineutrinos, corresponding to an average energy deposition rate of more than 1E52 erg/s and a total energy of about 1E50 erg deposited in electron-positron pairs around the collision site within 10ms. Although these numbers seem very favorable for gamma-ray burst scenarios, the pollution of the $e^\pm$ pair-plasma cloud with nearly 0.1$M_{\odot}$ of dynamically ejected baryons is 5 orders of magnitude too large. Therefore the formation of a relativistically expanding fireball that leads to a gamma-ray burst powered by neutrino emission from colliding neutron stars is definitely ruled out.