Diversities in the properties of neutron stars at a fixed neutron-skin thickness in $^{208}$Pb nucleus

TL;DR

This paper investigates how variations in the nuclear symmetry energy, modeled through different meson cross-couplings in the extended RMF framework, affect neutron star properties while maintaining a fixed neutron-skin thickness in lead-208.

Contribution

It introduces two families of extended RMF models with different cross-couplings that produce wide neutron-skin variations and explores their impact on neutron star characteristics.

Findings

Neutron star properties vary by 10-40% between model families.

Models with similar neutron-skin thickness can predict different neutron star radii.

Significant differences are observed in core-crust transition density and tidal polarizability.

Abstract

We study the diversities in the properties of the neutron stars arising due to the different choices for the cross-coupling between various mesons which governs the density dependence of the nuclear symmetry energy in the extended relativistic mean-field(RMF) model. For this purpose, we obtain two different families of the extended RMF model corresponding to different non-linear cross-coupling term in the isovector part of the effective Lagrangian density. The lowest order contributions for the $\delta$ mesons are also included. The different models within the same family are so obtained that they yield wide variation in the value of neutron-skin thickness in the $^{208}$Pb nucleus. These models are employed to compute the neutron star properties such as, core-crust transition density, radius and red shift at canonical mass ($1.4M_{\odot}$), tidal polarizability parameter, and threshold mass required for the enhanced cooling through direct Urca process. Most of the neutron star properties considered are significantly different(10\%-40\%) for the different families of models at a smaller neutron-skin thickness ($\sim 0.15$ fm) in the $^{208}$Pb nucleus.