The Nuclear Equation of State and Neutron Star Masses

TL;DR

This paper reviews how recent astrophysical observations, nuclear experiments, and theoretical studies collectively constrain the nuclear equation of state and neutron star properties, revealing a convergence in understanding dense matter.

Contribution

It synthesizes observational, experimental, and theoretical constraints to provide a comprehensive understanding of the nuclear equation of state and neutron star masses.

Findings

Mass measurements constrain high-density equation of state

Radius observations inform nuclear symmetry energy behavior

The convergence of constraints enhances understanding of dense matter

Abstract

Neutron stars are valuable laboratories for the study of dense matter. Recent observations have uncovered both massive and low-mass neutron stars and have also set constraints on neutron star radii. The largest mass measurements are powerfully influencing the high-density equation of state because of the existence of the neutron star maximum mass. The smallest mass measurements, and the distributions of masses, have implications for the progenitors and formation mechanisms of neutron stars. The ensemble of mass and radius observations can realistically restrict the properties of dense matter, and, in particular, the behavior of the nuclear symmetry energy near the nuclear saturation density. Simultaneously, various nuclear experiments are progressively restricting the ranges of parameters describing the symmetry properties of the nuclear equation of state. In addition, new theoretical studies of pure neutron matter are providing insights. These observational, experimental and theoretical constraints of dense matter, when combined, are now revealing a remarkable convergence.