Crust of accreting neutron stars within simplified reaction network

TL;DR

This paper introduces a simplified nuclear reaction network for modeling accreting neutron star crusts, accurately reproducing detailed models while highlighting the importance of nuclear mass tables and boundary treatments.

Contribution

The authors develop a simplified reaction network that efficiently models neutron star crust reactions, matching detailed results and emphasizing the impact of nuclear mass data choices.

Findings

The simplified network reproduces detailed model results well.

Composition and heating are sensitive to nuclear mass table choices.

Impurity parameter $Q_{imp}$ varies significantly with mass table and density.

Abstract

Transiently accreting neutron stars in low mass X-ray binaries are generally believed to be heated up by nuclear reactions in accreted matter during hydrostatic compression. Detailed modeling of these reactions is required for the correct interpretation of observations. In this paper, we construct a simplified reaction network, which can be easily implemented and depends mainly on atomic mass tables as nuclear physics input. We show that it reproduces results of the detailed network by Lau et al. (2018) very well, if one applies the same mass model. However, the composition and the heating power are shown to be sensitive to the mass table used and treatment of mass tables boundary, if one applies several of them in one simulation. In particular, the impurity parameter $Q_\mathrm{imp}$ at density $\rho=2\times 10^{12}$ g cm$^{-3}$ can differ for a factor of few, and even increase with density increase. The profile of integrated heat realize shown to be well confined between results by Fantina et al. (2018) and Lau et al. (2018).