Rotation-induced deep crustal heating of millisecond pulsars

TL;DR

This paper investigates how the spin-down of neutron stars causes crustal compression and nuclear reactions, leading to heating in recycled pulsars, and compares theoretical predictions with observations of thermal ultraviolet emission.

Contribution

It introduces a mechanism for deep crustal heating in millisecond pulsars caused by rotation-induced compression and nuclear reactions, providing quantitative estimates and observational comparisons.

Findings

The mechanism can explain the thermal ultraviolet emission of PSR J0437-4715.

Calculated emissivity aligns with observed heating levels.

Rotation-induced nuclear reactions significantly contribute to pulsar crust heating.

Abstract

The spin-down of a neutron star, e.g. due to magneto-dipole losses, results in compression of the stellar matter and induces nuclear reactions at phase transitions between different nuclear species in the crust. We show that this mechanism is effective in heating recycled pulsars, in which the previous accretion process has already been compressing the crust, so it is not in nuclear equilibrium. We calculate the corresponding emissivity and confront it with available observations, showing that it might account for the likely thermal ultraviolet emission of PSR J0437-4715.