Effects of the symmetry energy on properties of neutron star crusts near the neutron drip density

TL;DR

This paper investigates how the symmetry energy influences the neutron drip density and crust composition in neutron stars, highlighting the importance of finite-size effects and comparing different modeling approaches.

Contribution

It provides a detailed analysis of the impact of symmetry energy and its slope on neutron star crust properties using the Thomas--Fermi approximation within a relativistic mean-field framework.

Findings

Neutron drip density correlates with symmetry energy parameters.

Finite-size effects significantly affect crust equilibrium states.

Comparison shows the importance of surface and Coulomb energy treatments.

Abstract

We study the effects of the symmetry energy on the neutron drip density and properties of nuclei in neutron star crusts. The nonuniform matter around the neutron drip point is calculated by using the Thomas--Fermi approximation with the relativistic mean-field model. The neutron drip density and the composition of the crust are found to be correlated with the symmetry energy and its slope. We compare the self-consistent Thomas--Fermi approximation with other treatments of surface and Coulomb energies and find that these finite-size effects play an essential role in determining the equilibrium state at low density.