Nuclear constraints on the inner edge of neutron star crusts

TL;DR

This paper demonstrates that common approximations in modeling neutron star matter can lead to overestimations of the core-crust transition point, and it constrains these parameters using experimental data, impacting neutron star models.

Contribution

It provides new constraints on the density and pressure at the neutron star inner crust boundary based on experimental data, improving the accuracy of neutron star models.

Findings

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

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

Implications for Vela pulsar modeling

Abstract

We show that the widely used parabolic approximation to the Equation of State (EOS) of asymmetric nuclear matter leads systematically to significantly higher core-crust transition densities and pressures. Using an EOS for neutron-rich nuclear matter constrained by the isospin diffusion data from heavy-ion reactions in the same sub-saturation density range as the neutron star crust, the density and pressure at the inner edge separating the liquid core from the solid crust of neutron stars are determined 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. Implications of these constraints on the Vela pulsar are discussed.