Constraints on the maximum densities of neutron stars from postmerger gravitational waves with third-generation observations

TL;DR

This paper establishes a universal relation linking postmerger gravitational-wave frequency to neutron star core density, enabling precise constraints on the equation of state and maximum neutron star mass with future gravitational-wave detectors.

Contribution

It introduces a robust quasi-universal relation derived from simulations that connects postmerger GW features to neutron star core density, aiding future observational constraints.

Findings

Bayesian inference can constrain maximum density to ~15% with a single event.

Including postmerger signals improves constraints on the pressure-density relation.

Maximum neutron star mass can be measured with better than 12% accuracy.

Abstract

Using data from 289 numerical relativity simulations of merging binary neutron stars, we identify, for the first time, a robust quasi-universal relation connecting the postmerger peak gravitational-wave frequency and the value of the density at the center of the maximum mass nonrotating neutron star. This relation offers a new possibility for precision equation-of-state constraints with next-generation ground-based gravitational-wave interferometers. Mock Einstein Telescope observations of fiducial events indicate that Bayesian inferences can constrain the maximum density to ${\sim}15\%$ ($90\%$ confidence level) for a single signal at the minimum sensitivity threshold for a detection. If the postmerger signal is included in a full-spectrum (inspiral-merger-postmerger) analysis of such signal, the pressure-density function can be tightly constrained up to the maximum density, and the maximum neutron star mass can be measured with an accuracy better than $12\%$ ($90\%$ confidence level).