Neutron Star Crustal Mass Fractions

TL;DR

This study models the cooling and nuclear composition of neutron star crusts over one year, revealing the dominant isotopes and their distribution at various depths using a nuclear reaction network.

Contribution

It introduces a detailed calculation of crustal mass fractions after cooling, incorporating a nuclear reaction network up to technetium and specific cooling curves.

Findings

$^{28}$Si remains the lightest optically thick isotope after one year.

Nuclear composition varies with depth in the neutron star crust.

Cooling curves influence the distribution of nuclei in the crust.

Abstract

We are investigating mass fractions on the crust of a neutron star which would remain after one year of cooling. We use cooling curves corresponding with various densities, or depths, of the neutron star just after its formation. We assume the modified Urca process dominates the energy budget of the outer layers of the star in order to calculate the temperature of the neutron star as a function of time. Using a nuclear reaction network up to technetium, we calculate how the distribution of nuclei quenches at various depths of the neutron star crust. The initial results indicate that $^{28}$Si is the lightest isotope to be optically thick on the surface after one year of cooling.