Neutron Star Cooling Within the Equation of State With Induced Surface Tension

Abstract

We study the thermal evolution of neutron stars described within the equation of state with induced surface tension (IST) that reproduces properties of normal nuclear matter, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision experiments, and it is equally compatible with the constraints from astrophysical observations and the GW170817 event. The model features strong direct Urca processes for the stars above 1.91M⊙. The IST equation of state shows very good agreement with the available cooling data, even without introducing nuclear pairing. We also analysed the effect of the singlet proton/neutron and triplet neutron pairing on the cooling of neutron stars of different mass. We show that the description of the compact object in the center of the Cassiopeia A does not necessarily require an inclusion of neutron superfluidity and/or proton superconductivity. Our results indicate that data of Cassiopeia A can be adequately well reproduced by a 1.66M⊙ star with an atmosphere of light elements. Moreover, the IST EoS reproduces each of the observational datasets for the surface temperature of Cassiopeia A either by a rapidly cooling ∼1.955M⊙ star with paired and unpaired matter or by a 1.91M⊙ star with the inclusion of neutron and proton pairings in the singlet channel.

Thermal evolution of neutron stars described within the equation of state with induced surface tension

“…The inclusion of the neutron pairing in the triplet channel, occurring in the NS core, led to an accelerated cooling, F I G U R E 3 The same as Figure 2, but supplemented with neutron superfluidity in the 1 S 0 channel following the SFB model (Schwenk et al 2003) and proton superconductivity in the 1 S 0 channel following the AO model (Amundsen & Østgaard 1985a) (upper panel) and CCDK model (Chen et al 1993) (lower panel) and further inconsistency with the observational data (for details see Tsiopelas & Sagun (2020)).…”

“…The inclusion of the neutron pairing in the triplet channel, occurring in the NS core, led to an accelerated cooling, and further inconsistency with the observational data (for details see Tsiopelas & Sagun (2020)).…”

The Impact of Asymmetric Dark Matter on the Thermal Evolution of Nucleonic and Hyperonic Compact Stars

“…As it was shown in Ref. [139], the IST EoS does not necessarily require the incorporation of the neutron superfluidity and/or proton conductivity to explain the Cas A temperature drop. The model reproduced the Cas A data with 1.66 M ⊙ and 1.91 M ⊙ stars with the inclusion of neutron and proton singlet pairings, as well as with the 1.96 M ⊙ star for unpaired matter [140].…”