Nuclear physics with gravitational waves from neutron stars disrupted by black holes

TL;DR

This paper develops a model to analyze gravitational waves from neutron star-black hole mergers, demonstrating that such signals can constrain neutron star radii, but with less precision than binary neutron star mergers.

Contribution

It introduces a phenomenological model for tidal disruption signatures in gravitational waves and assesses the measurement precision of neutron star radii using future detectors.

Findings

A two-detector Cosmic Explorer network can measure disruption time with 0.5 ms precision.

Disruption time measurement constrains neutron star radius to within 0.7 km.

Constraints from NSBH mergers are less tight than those from binary neutron star mergers.

Abstract

Gravitational waves from neutron star-black hole (NSBH) mergers that undergo tidal disruption provide a potential avenue to study the equation of state of neutron stars and hence the behaviour of matter at its most extreme densities. We present a phenomenological model for the gravitational-wave signature of tidal disruption, which allows us to measure the disruption time. We carry out a study with mock data, assuming an optimistically nearby NSBH event with parameters optimised for measuring the tidal disruption. We show that a two-detector network of 40 km Cosmic Explorer instruments can measure the time of disruption with a precision of 0.5 ms, which corresponds to a constraint on the neutron star radius of 0.7 km (90\% credibility). This radius constraint is wider than the constraint obtained by measuring the tidal deformability of the neutron star of the same system during the inspiral. Moreover, the neutron star radius is likely to be more tightly constrained using binary neutron star mergers. While NSBH mergers are important for the information they provide about stellar and binary astrophysics, they are unlikely to provide insights into nuclear physics beyond what we will already know from binary neutron star mergers.