Signature of deconfinement with spin down compression in cooling hybrid stars

TL;DR

This paper investigates how the phase transition to deconfined quark matter in hybrid neutron stars affects their cooling and surface temperature evolution during spin down, revealing a potential signature of deconfinement.

Contribution

It introduces a self-consistent model coupling spin down, phase transitions, and thermal evolution, highlighting the impact of latent heat and superfluidity on neutron star cooling.

Findings

Deconfinement delays neutron star cooling.

Latent heat reinforces temperature increase during quark core formation.

Superfluidity influences the thermal signature of phase transition.

Abstract

The thermal evolution of neutron stars is coupled to their spin down and the resulting changes in structure and chemical composition. This coupling correlates stellar surface temperatures with rotational state as well as time. We report an extensive investigation of the coupling between spin down and cooling for hybrid stars which undergo a phase transition to deconfined quark matter at the high densities present in stars at low rotation frequencies. The thermal balance of neutron stars is re-analyzed to incorporate phase transitions and the related latent heat self-consistently, and numerical calculations are undertaken to simultaneously evolve the stellar structure and temperature distribution. We find that the changes in stellar structure and chemical composition with the introduction of a pure quark matter phase in the core delay the cooling and produce a period of increasing surface temperature for strongly superfluid stars of strong and intermediate magnetic field strength. The latent heat of deconfinement is found to reinforce this signature if quark matter is superfluid and it can dominate the thermal balance during the formation of a pure quark matter core. At other times it is less important and does not significantly change the thermal evolution.