Simultaneously Constraining the Neutron Star Equation of State and Mass Distribution through Multimessenger Observations and Nuclear Benchmarks

TL;DR

This study combines nuclear theory, experiments, and multimessenger astrophysical data within a Bayesian framework to tightly constrain the neutron star equation of state and mass distribution, highlighting the impact of low-density nuclear physics.

Contribution

It introduces a hybrid EOS model integrating empirical and piecewise polytrope approaches and demonstrates the significant constraining power of $ ext{chi}$EFT data on the EOS.

Findings

$ ext{chi}$EFT data significantly tighten low-density EOS constraints.

pQCD and nuclear experiments have minimal impact on EOS constraints.

Hierarchical Bayesian analysis effectively combines diverse observational and experimental data.

Abstract

With ongoing advancements in nuclear theory and experimentation, together with a growing body of neutron star (NS) observations, a wealth of information on the equation of state (EOS) for matter at extreme densities has become accessible. Here, we utilize a hybrid EOS formulation that combines an empirical parameterization centered around the nuclear saturation density with a generic three-segment piecewise polytrope model at higher densities. We incorporate data derived from chiral effective field theory ($\chi$EFT), perturbative quantum chromodynamics (pQCD), and from experiments such as PREX-II and CREX. Furthermore, we examine the influence of a total of 129 NS mass measurements up to April 2023, as well as simultaneous mass and radius measurements derived from the X-ray emission from surface hot spots on NSs. Additionally, we consider constraints on tidal properties inferred from the gravitational waves emitted by coalescing NS binaries. To integrate this extensive and varied array of constraints, we utilize a hierarchical Bayesian statistical framework to simultaneously deduce the EOS and the distribution of NS masses. We find that incorporating data from $\chi$EFT significantly tightens the constraints on the EOS of NSs near or below the nuclear saturation density. However, constraints derived from pQCD computations and nuclear experiments such as PREX-II and CREX have minimal impact.