Abstract
The standard cooling scenario in the presence of nucleon superfluidity fits rather well to the observation of the neutron stars. It implies that the stellar cooling arguments could place a stringent constraint on the properties of novel particles. We study in particular the cooling rate induced by dark gauge bosons for very young neutron stars: remnants of Cassiopeia A and SN1987A. The cooling is dominantly contributed either by the nucleon pair breaking and formation in the core or by the electron bremsstrahlung in the crust, depending on the age of the stars and the form of the couplings. We compute how much the cooling curve of the young neutron stars could be modified by the extra dark gauge boson emission and obtain the bound for the dark gauge boson when its mass is lower than $\mathcal{O}(0.1)\text{ }\text{ }\mathrm{MeV}$; for the dark photon, we find the mixing parameter times its mass $ϵ{m}_{{\ensuremath{\gamma}}^{\ensuremath{'}}}<1.5\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{MeV}$ and for the $\mathrm{U}(1{)}_{B\ensuremath{-}L}$ gauge boson its coupling to nucleons and electrons ${e}^{\ensuremath{'}}<5\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}13}$. We also discuss the possibility that the rapid cooling of Cas A might provide a hint for the existence of the $\mathrm{U}(1{)}_{B\ensuremath{-}L}$ gauge boson of mass around eV and its coupling ${e}^{\ensuremath{'}}\ensuremath{\sim}1{0}^{\ensuremath{-}13}$.
Highlights
Neutron stars (NSs) are one of the typical remnants in the core of supernova explosion and considered as the densest objects, directly observed in nature
We study in particular the cooling rate induced by dark gauge bosons for very young neutron stars: remnants of Cassiopeia A and SN1987A
We compute how much the cooling curve of the young neutron stars could be modified by the extra dark gauge boson emission and obtain the bound for the dark gauge boson when its mass is lower than Oð0.1Þ MeV; for the dark photon, we find the mixing parameter times its mass εmγ0 < 1.5 × 10−8 MeV and for the Uð1ÞB−L gauge boson its coupling to nucleons and electrons e0 < 5 × 10−13
Summary
Neutron stars (NSs) are one of the typical remnants in the core of supernova explosion and considered as the densest objects, directly observed in nature. If further observations of Cas A confirm the cooling curve including the PBF process, that would be the first direct evidence of the superfluidity in NSs, which was predicted long ago [11] Another NS showing its early history is the conjectured compact object in the remnant of SN1987A, which is dubbed NS1987A. Through the recent observations attained by the Atacama Large Millimeter Array with its high angular resolution, it was identified from the infrared excess of a local dust blob near the predicted location of a kicked compact remnant [12] This strongly suggests the presence of the neutron star as a cooling remnant [13]. We provide new constraints on the existence of light dark particles with certain couplings, based on the fact that the thermal histories of Cas A and NS1987A fit well with the standard cooling curves.
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