Neutron star tidal disruption in mixed binaries: the imprint of the equation of state

TL;DR

This paper investigates how neutron star tidal disruption in black hole-neutron star binaries affects gravitational wave signals, showing that the cutoff frequency can reveal neutron star radius and matter properties.

Contribution

It introduces a method to determine neutron star radius from gravitational wave cutoff frequency, linking waveform features to the star's equation of state.

Findings

Disruption occurs before the innermost stable circular orbit for certain conditions.

The cutoff frequency nu_GWtide can be used to measure neutron star radius with high precision.

Gravitational wave signals contain signatures of the neutron star's internal matter properties.

Abstract

We study the tidal disruption of neutron stars in black hole-neutron star coalescing binaries. We calculate the critical orbital separation at which the star is disrupted by the black hole tidal field for several equations of state describing the matter inside the neutron star, and for a large set of the binary parameters. When the disruption occurs before the star reaches the innermost stable circular orbit, the gravitational wave (GW) signal emitted by the system is expected to exhibit a cutoff frequency nu_GWtide, which is a distinctive feature of the waveform. We evaluate nu_GWtide and show that, if this frequency will be found in a detected gravitational wave, it will allow to determine the neutron star radius with an error of a few percent, providing valuable information on the behaviour of matter in the stellar core.