Nuclear Physics of the Outer Layers of Accreting Neutron Stars

TL;DR

This review summarizes the current understanding of the nuclear physics in the outer layers of accreting neutron stars, highlighting how nuclear reactions influence observable phenomena and the challenges in modeling these systems.

Contribution

It provides a comprehensive overview of recent advances in nuclear physics related to accreting neutron stars and discusses the integration of astronomical observations with nuclear theory.

Findings

Nuclear burning alters the composition of neutron star crusts.

Compression-driven reactions impact thermal and chemical structures.

Astronomical data offers new tests for nuclear physics models.

Abstract

Now 50 years since the existence of the neutron star crust was proposed, we review the current understanding of the nuclear physics of the outer layers of accreting neutron stars. Nuclei produced during nuclear burning replace the nascent composition of the neutron star ocean and crust. Non-equilibrium nuclear reactions driven by compression alter the outer thermal structure and chemical composition, leaving observable imprints on astronomical phenomena. As observations of bursting neutron stars and cooling neutron stars have increased, the recent volume of astronomical data allows new insights into the microphysics of the neutron star interior and the possibility to test nuclear physics input in model calculations. Despite numerous advances in our understanding of neutron star interiors and observed neutron star phenomena, many challenges remain in the astrophysics theory of accreting neutron stars, the nuclear theory of neutron-rich nuclei, and the reach and precision of terrestrial nuclear physics experiments.