Revised Relativistic Hydrodynamical Model for Neutron-Star Binaries

TL;DR

This paper presents a revised hydrodynamic simulation of binary neutron-star mergers, showing reduced compression effects and improved agreement with post-Newtonian models, with implications for neutron star stability prior to merger.

Contribution

The study introduces a corrected hydrodynamic model that accounts for recent findings, reducing compression effects and aligning orbital frequencies with theoretical expectations.

Findings

Compression is significantly reduced but not eliminated.

Inner most stable circular orbit shifts closer.

Orbital frequencies now match post-Newtonian predictions.

Abstract

We report on numerical results from a revised hydrodynamic simulation of binary neutron-star orbits near merger. We find that the correction recently identified by Flanagan significantly reduces but does not eliminate the neutron-star compression effect. Although results of the revised simulations show that the compression is reduced for a given total orbital angular momentum, the inner most stable circular orbit moves to closer separation distances. At these closer orbits significant compression and even collapse is still possible prior to merger for a sufficiently soft EOS. The reduced compression in the corrected simulation is consistent with other recent studies of rigid irrotational binaries in quasiequilibrium in which the compression effect is observed to be small. Another significant effect of this correction is that the derived binary orbital frequencies are now in closer agreement with post-Newtonian expectations.