Evolution of Close Neutron Star Binaries

TL;DR

This paper models the evolution of neutron star binaries towards merger, incorporating relativistic, hydrodynamical, and tidal effects, and examines how stellar structure influences gravitational wave signals.

Contribution

It introduces a comprehensive model including post-2.5 Newtonian and tidal effects, highlighting the impact of stellar structure on binary evolution and gravitational waveforms.

Findings

Stellar structure significantly affects gravitational waveforms.

Internal stellar deformation influences orbital dynamics.

Relativistic and hydrodynamical effects are crucial in the final merger phase.

Abstract

We have calculated evolution of neutron star binaries towards the coalescence driven by gravitational radiation. The hydrodynamical effects as well as the general relativistic effects are important in the final phase. All corrections up to post$^{2.5}$-Newtonian order and the tidal effect are included in the orbital motion. The star is approximated by a simple Newtonian stellar model called affine star model. Stellar spins and angular momentum are assumed to be aligned. We have showed how the internal stellar structure affects the stellar deformation, variations of the spins, and the orbital motion of the binary just before the contact. The gravitational wave forms from the last a few revolutions significantly depend on the stellar structure.