Constraining neutron star properties with a new equation of state insensitive approach

TL;DR

This paper introduces a new method to constrain neutron star properties by parameterizing macroscopic relations, enabling improved inference of the equation of state from combined electromagnetic and gravitational wave observations.

Contribution

The authors develop a novel parameterization of R(M) and Lambda(M) relations that accurately approximate various EoSs, enhancing neutron star property inference from multi-messenger data.

Findings

Estimated neutron star radius at 1.4 solar masses: 12.05 km

Inferred maximum neutron star mass: 2.52 solar masses

Constrained neutron star deformability and radius with combined observations

Abstract

Instead of parameterizing the pressure-density relation of a neutron star (NS), one can parameterize its macroscopic properties such as mass ($M$), radius ($R$), and dimensionless tidal deformability ($\Lambda$) to infer the equation of state (EoS) combining electromagnetic and gravitational wave (GW) observations. We present a new method to parameterize $R(M)$ and $\Lambda(M)$ relations, which approximate the candidate EoSs with accuracy better than 5\% for all masses and span a broad region of $M-R-\Lambda$ plane. Using this method we combine the $M-\Lambda$ measurement from GW170817 and GW190425, and simultaneous $M-R$ measurement of PSR J0030+0451 and PSR J0740+6620 to place joint constraints on NS properties. At 90 \% confidence, we infer $R_{1.4}=12.05_{-0.87}^{+0.98}$ km and $\Lambda_{1.4}=372_{-150}^{+220}$ for a $1.4 M_{\odot}$ NS, and $R_{2.08}=12.65_{-1.46}^{+1.36}$ km for a $2.08 M_{\odot}$ NS. Furthermore, we use the inferred values of the maximum mass of a nonrotating NS $M_{\rm max}=2.52_{-0.29}^{+0.33} M_{\odot}$ to investigate the nature of the secondary objects in three potential neutron star-black hole merger (NSBH) system.