Strangeness in Neutron Star Cooling

Yeunhwan Lim, Chang Ho Hyun, Chang Hwan Lee

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We study the thermal evolution of neutron stars in the presence of hyperons or kaons in the core. Our results indicate that the nucleon and the hyperon direct Urca processes play crucial roles for macroscopic cooling behavior of neutron stars. The presence of hyperons drives fast cooling mechanisms in two ways: 1) it allows the hyperon direct Urca prior to the nucleon direct Urca, and 2) it makes the nucleon direct Urca more feasible by reducing the neutron Fermi momentum. All of the equations of state (EOSs) used in this work satisfy the maximum mass constraints and the allowed areas of mass and radii of neutron stars. We found that the neutron star EOS with hyperons can still be consistent with both mass and temperature observations if the original neutron star’s EOS without hyperons is stiff enough. On the other hand, we found that the neutron star’s EOS with kaons can be consistent only with mass observations, but can hardly explain the cooling behavior if we take into account the statistical distribution of observed neutron star masses.

Original languageEnglish
Pages (from-to)547-554
Number of pages8
JournalJournal of the Korean Physical Society
Issue number6
StatePublished - 1 Mar 2019

Bibliographical note

Funding Information:
YL was partially supported by the U.S. National Science Foundation under Grant No. PHY1652199. CHH was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (No. 2017R1D1A1B03029020 and No. 2018R1A5A10255 63). CHL was supported by the National Research Foundation of Korea (NRF) grants funded by the Korea government (Ministry of Sciencd and ICT and Ministry of Education) (No. 2016R1A5A1013277 and No. 2018R1D1 A1B07048599).

Publisher Copyright:
© 2019, The Korean Physical Society.


  • Cooling
  • Neutron stars
  • Strangeness


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