Irrotational binary neutron stars in quasiequilibrium

TL;DR

This paper presents an independent numerical analysis of irrotational binary neutron stars in quasi-equilibrium, challenging previous simulations by showing a much smaller density increase before the last orbit.

Contribution

It introduces an independent formalism to model binary neutron stars, providing a critical test against prior hydrodynamic simulation results.

Findings

Interior density increases slightly near last orbits

The effect is much smaller than previously reported

Supports the stability of neutron stars in close binaries

Abstract

We report on numerical results from an independent formalism to describe the quasi-equilibrium structure of nonsynchronous binary neutron stars in general relativity. This is an important independent test of controversial numerical hydrodynamic simulations which suggested that nonsynchronous neutron stars in a close binary can experience compression prior to the last stable circular orbit. We show that, for compact enough stars the interior density increases slightly as irrotational binary neutron stars approach their last orbits. The magnitude of the effect, however, is much smaller than that reported in previous hydrodynamic simulations.