Non-uniform Matter in Neutron Star Crusts Studied by the Variational Method with Thomas-Fermi Calculations

TL;DR

This paper develops a detailed equation of state for neutron star crusts using the variational method and Thomas-Fermi calculations, aligning well with experimental nuclear data and providing insights into crust composition and density profiles.

Contribution

It introduces a refined EOS for neutron star crusts based on variational nuclear matter calculations and Thomas-Fermi approximation, calibrated to experimental nuclear data.

Findings

Proton numbers in NS crust nuclei are consistent with Negele and Vautherin.

The EOS predicts larger proton numbers than Shen et al. due to symmetry energy differences.

Density profiles of neutron stars are derived from the constructed EOS.

Abstract

The equation of state (EOS) for neutron star (NS) crusts is studied in the Thomas-Fermi (TF) approximation using the EOS for uniform nuclear matter obtained by the variational method with the realistic nuclear Hamiltonian. The parameters associated with the nuclear three-body force, which are introduced to describe the saturation properties, are finely adjusted so that the TF calculations for isolated atomic nuclei reproduce the experimental data on masses and charge distributions satisfactorily. The resulting root-mean-square deviation of the masses from the experimental data for mass-measured nuclei is about 3 MeV. With use of the nuclear EOS thus determined, the nuclei in the crust of NS at zero temperature are calculated. The predicted proton numbers of the nuclei in the crust of NS are close to the gross behavior of the results by Negele and Vautherin, while they are larger than those for the EOS by Shen et al. due to the difference in the symmetry energy. The density profile of NS is calculated with the constructed EOS.