Transition Density and Pressure at the Inner Edge of Neutron Star Crusts

TL;DR

This paper uses recent experimental constraints on nuclear symmetry energy to accurately determine the transition density and pressure at the inner edge of neutron star crusts, improving neutron star models.

Contribution

It provides new estimates of transition density and pressure using constrained symmetry energy, and highlights the impact of approximation methods on these values.

Findings

Transition density range: 0.040-0.065 fm$^{-3}$

Transition pressure range: 0.01-0.26 MeV/fm$^{3}$

Improved mass-radius relation for neutron stars

Abstract

Using the nuclear symmetry energy that has been recently constrained by the isospin diffusion data in intermediate-energy heavy ion collisions, we have studied the transition density and pressure at the inner edge of neutron star crusts, and they are found to be 0.040 fm$^{-3}$ $\leq \rho_{t}\leq 0.065$ fm$^{-3}$ and 0.01 MeV/fm$^{3}$ $\leq P_{t}\leq 0.26$ MeV/fm$^{3}$, respectively, in both the dynamical and thermodynamical approaches. We have also found that the widely used parabolic approximation to the equation of state of asymmetric nuclear matter gives significantly higher values of core-crust transition density and pressure, especially for stiff symmetry energies. With these newly determined transition density and pressure, we have obtained an improved relation between the mass and radius of neutron stars.