Measuring the nuclear equation of state with neutron star-black hole mergers

TL;DR

This paper introduces a novel non-parametric Gaussian process method to infer the nuclear equation of state from neutron star-black hole merger gravitational-wave data, providing precise constraints on neutron star properties.

Contribution

The authors develop a new non-parametric Gaussian process approach for EOS inference, enabling direct constraints on pressure at specific densities and correlation length-scales from GW observations.

Findings

GW detector network at O5 sensitivities can measure NS radius with 1.6% precision.

Maximum NS mass can be constrained with 13% accuracy.

Projected correlation length-scale constraint is ≥ 3.2 MeV fm^{-3}.

Abstract

Gravitational-wave (GW) observations of neutron star-black hole (NSBH) mergers are sensitive to the nuclear equation of state (EOS). We present a new methodology for EOS inference with non-parametric Gaussian process (GP) priors, enabling direct constraints on the pressure at specific densities and the length-scale of correlations on the EOS. Using realistic simulations of NSBH mergers, incorporating both GW and electromagnetic (EM) selection to ensure sample purity, we find that a GW detector network operating at O5-sensitivities will constrain the radius of a $\unit[1.4]{M_{\odot}}$ NS and the maximum NS mass with $1.6\%$ and $13\%$ precision, respectively. With the same sample, the projected constraint on the length-scale of correlations in the EOS is $\geq~\unit[3.2]{MeV~fm^{-3}}$. These results demonstrate strong potential for insights into the nuclear EOS from NSBH systems, provided they are robustly identified.