Neutron Star Inner Crust at Finite Temperatures: A Comparison Between Compressible Liquid Drop and Extended Thomas-Fermi Approaches

TL;DR

This paper compares two theoretical models, CLDM and TETF, for predicting the properties of neutron star inner crusts at finite temperatures, finding good agreement but noting some limitations of CLDM.

Contribution

It provides a systematic comparison between CLDM and TETF approaches, highlighting their agreement and differences in modeling neutron star crusts at finite temperatures.

Findings

CLDM and TETF show good agreement on thermodynamic properties.

CLDM can reproduce TETF composition with optimized surface energy.

Neglect of neutron skin in CLDM causes proton radius overestimation.

Abstract

We investigate the effects of temperature on the properties of the inner crust of a non-accreting neutron star. To this aim, we employ two different treatments: the compressible liquid drop model (CLDM) and the temperature-dependent extended Thomas-Fermi (TETF) method. Our systematic comparison shows an agreement between the two methods on their predictions for the crust thermodynamic properties. We find that the CLDM description can also reproduce reasonably well the TETF composition especially if the surface energy is optimized on the ETF calculation. However, the neglect of neutron skin in CLDM leads to an overestimation of the proton radii.