The equation of state for dense nucleonic matter from a meta-modeling. II. Predictions for neutron stars properties

TL;DR

This study uses a meta-modeling approach to analyze neutron star properties, revealing a near-universal equation of state behavior, and highlights key empirical parameters influencing neutron star radii within nuclear physics constraints.

Contribution

It introduces a Bayesian meta-modeling framework for the nucleonic matter equation of state, analyzing neutron star properties and the impact of empirical parameter uncertainties.

Findings

Neutron star radii are approximately 12.7 km for 1-2 solar mass stars.

A radius below 11 km is marginally compatible with current nuclear parameter knowledge.

The slope and curvature of the symmetry energy significantly influence neutron star radii.

Abstract

Employing a recently proposed metamodeling for the nucleonic matter equation of state we analyze neutron star global properties such as masses, radii, momentum of inertia, and others. The impact of the uncertainty on empirical parameters on these global properties is analyzed in a Bayesian statistical approach. Physical constraints, such as causality and stability, are imposed on the equation of state and different hypotheses for the direct Urca (dUrca) process are investigated. In addition, only metamodels with maximum masses above 2$M_\odot$ are selected. Our main results are the following: the equation of state exhibits a universal behavior against the dUrca hypothesis under the condition of charge neutrality and $\beta$-equilibrium; neutron stars, if composed exclusively of nucleons and leptons, have a radius of 12.7$\pm$0.4~km for masses ranging from 1 up to 2$M_\odot$; a small radius lower than 11~km is very marginally compatible with our present knowledge of the nuclear empirical parameters; and finally, the most important empirical parameters which are still affected by large uncertainties and play an important role in determining the radius of neutrons stars are the slope and curvature of the symmetry energy ($L_{sym}$ and $K_{sym}$) and, to a lower extent, the skewness parameters ($Q_{sat/sym}$).