Numerical models of irrotational binary neutron stars in general relativity

TL;DR

This paper presents relativistic models of irrotational binary neutron stars in circular orbits, showing that they do not tend to collapse into black holes before merging, with implications for gravitational wave predictions.

Contribution

It introduces a method to compute quasiequilibrium irrotational binary neutron star configurations using the conformally flat approximation in general relativity.

Findings

Neutron stars' central density decreases less than in corotating cases

No evidence of individual collapse to black holes before merger

Sequences of constant baryon number analyzed

Abstract

We report on general relativistic calculations of quasiequilibrium configurations of binary neutron stars in circular orbits with zero vorticity. These configurations are expected to represent realistic situations as opposed to corotating configurations. The Einstein equations are solved under the assumption of a conformally flat spatial 3-metric (Wilson-Mathews approximation). The velocity field inside the stars is computed by solving an elliptical equation for the velocity scalar potential. Results are presented for sequences of constant baryon number (evolutionary sequences). Although the central density decreases much less with the binary separation than in the corotating case, it still decreases. Thus, no tendency is found for the stars to individually collapse to black hole prior to merger.