Cooling of Accretion-Heated Neutron Stars

TL;DR

This paper reviews observational studies of neutron star cooling post-accretion, highlighting how crust and core temperatures inform us about neutron star physics, including effects of magnetic fields.

Contribution

It provides a comprehensive overview of crust cooling observations and their implications for understanding neutron star interior physics, including magnetic field influences.

Findings

Crust cooling observations reveal details about neutron star crust properties.

Long-term temperature measurements inform about core thermal states.

Magnetic fields may significantly affect neutron star heating and cooling processes.

Abstract

We present a brief, observational review about the study of the cooling behaviour of accretion-heated neutron stars and the inferences about the neutron-star crust and core that have been obtained from these studies. Accretion of matter during outbursts can heat the crust out of thermal equilibrium with the core and after the accretion episodes are over, the crust will cool down until crust-core equilibrium is restored. We discuss the observed properties of the crust cooling sources and what has been learned about the physics of neutron-star crusts. We also briefly discuss those systems that have been observed long after their outbursts were over, i.e, during times when the crust and core are expected to be in thermal equilibrium. The surface temperature is then a direct probe for the core temperature. By comparing the expected temperatures based on estimates of the accretion history of the targets with the observed ones, the physics of neutron-star cores can be investigated. Finally, we discuss similar studies performed for strongly magnetized neutron stars in which the magnetic field might play an important role in the heating and cooling of the neutron stars.