Delayed Thermal Relaxation of Rapidly Cooling Neutron Stars: Nucleon Superfluidity and Non-nucleon Particles

Fuente: arXiv
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Autores principales: Tu, Zhonghao, Li, Ang
Formato: Preprint
Publicado: 2025
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author Tu, Zhonghao
Li, Ang
author_facet Tu, Zhonghao
Li, Ang
contents The thermal relaxation time of neutron stars, typically defined by a sudden drop in surface temperature, is usually on the order of 10 to 100 years. In this study, we investigate neutron star thermal relaxation by incorporating nucleon superfluidity and non-nucleonic particles, specifically considering hyperons as a representative case. We find that rapidly cooling neutron stars driven by neutron superfluidity and direct Urca processes demonstrate delayed thermal relaxation under specific physical conditions. The former acquires that the neutron $^3P_2$ critical temperature is small enough, whereas the latter depends on the presence of a small core that permits direct Urca processes. To explore these scenarios, we propose simple theoretical frameworks to describe these delayed thermal relaxation behaviors and discuss how an recently-established enhanced modified Urca rate influences the relaxation time. By confronting the theoretical results with the observation of Cassiopeia A, we can effectively constrain the maximum neutron $^3P_2$ critical temperature.
format Preprint
id arxiv_https___arxiv_org_abs_2503_14059
institution arXiv
publishDate 2025
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spellingShingle Delayed Thermal Relaxation of Rapidly Cooling Neutron Stars: Nucleon Superfluidity and Non-nucleon Particles
Tu, Zhonghao
Li, Ang
Nuclear Theory
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
The thermal relaxation time of neutron stars, typically defined by a sudden drop in surface temperature, is usually on the order of 10 to 100 years. In this study, we investigate neutron star thermal relaxation by incorporating nucleon superfluidity and non-nucleonic particles, specifically considering hyperons as a representative case. We find that rapidly cooling neutron stars driven by neutron superfluidity and direct Urca processes demonstrate delayed thermal relaxation under specific physical conditions. The former acquires that the neutron $^3P_2$ critical temperature is small enough, whereas the latter depends on the presence of a small core that permits direct Urca processes. To explore these scenarios, we propose simple theoretical frameworks to describe these delayed thermal relaxation behaviors and discuss how an recently-established enhanced modified Urca rate influences the relaxation time. By confronting the theoretical results with the observation of Cassiopeia A, we can effectively constrain the maximum neutron $^3P_2$ critical temperature.
title Delayed Thermal Relaxation of Rapidly Cooling Neutron Stars: Nucleon Superfluidity and Non-nucleon Particles
topic Nuclear Theory
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2503.14059