Constraining the Neutron Star Radius with Joint Gravitational-Wave and Short Gamma-Ray Burst Observations of Neutron Star-Black Hole Coalescing Binaries

TL;DR

This paper proposes a method to measure neutron star radii by combining gravitational-wave and short gamma-ray burst observations of neutron star-black hole mergers, potentially constraining the neutron star equation of state with about 20% accuracy.

Contribution

It introduces a novel approach to determine neutron star radii using joint GW and SGRB data, enhancing constraints on neutron star physics.

Findings

Neutron star radius can be constrained to within 20% accuracy.

Joint GW and SGRB observations improve neutron star equation of state constraints.

Realistic detection scenarios with S/N of 10 are considered.

Abstract

Coalescing neutron star (NS)-black hole (BH) binaries are promising sources of gravitational-waves (GWs) to be detected within the next few years by current GW observatories. If the NS is tidally disrupted outside the BH innermost stable circular orbit, an accretion torus may form, and this could eventually power a short gamma-ray burst (SGRB). The observation of an SGRB in coincidence with gravitational radiation from an NS-BH coalescence would confirm the association between the two phenomena and also give us new insights on NS physics. We present here a new method to measure NS radii and thus constrain the NS equation of state using joint SGRB and GW observations of NS-BH mergers. We show that in the event of a joint detection with realistic GW signal-to-noise ratio (S/N) of 10, the NS radius can be constrained to $\lesssim\,$20% accuracy at 90% confidence.