Stellar properties and nuclear matter constraints

TL;DR

This paper evaluates relativistic mean-field models for neutron star properties, confirming which models meet nuclear matter constraints, maximum mass limits, and sound velocity bounds, and discusses the impact of hyperons and the sigma-cut scheme.

Contribution

It identifies RMF parametrizations consistent with nuclear matter constraints and neutron star observations, and explores the effects of hyperons and the sigma-cut scheme on these models.

Findings

Only two RMF models do not allow the direct Urca process.

Fourteen models produce neutron stars with maximum masses between 1.93 and 2.05 solar masses.

Models satisfying mass constraints do not violate the sound velocity bound.

Abstract

We have analyzed stellar properties of the relativistic mean-field (RMF) parametrizations shown to be consistent with the recently studied constraints related to nuclear matter, pure neutron matter, symmetry energy and its derivatives [Dutra et al., Phys. Rev. C 90, 055203 (2014)]. Our results show that only two RMF parametrizations do not allow the emergence of the direct Urca process, important aspect regarding the evolution of a neutron star. Moreover, among all approved RMF models, fourteen of them produce neutron stars with maximum masses inside the range $1.93\leqslant M/M_\odot\leqslant 2.05$, with $M_\odot$ being the solar mass. Only three models yield maximum masses above this range and a discussion on the inclusion of hyperons is presented. Finally, we have verified that the models satisfying the neutron star maximum mass constraint do not observe the squared sound velocity bound, namely, $v_s^2 < 1/3$, corroborating recent findings. However, the recently proposed $\sigma$-cut scheme can make the RMF models consistent with both constraints depending on the isoscalar-vector interaction of each parametrization.