Superfluidity of ${\Sigma }^{-}$ hyperons in $\beta$-stable neutron star matter

Abstract

In this work we evaluate the ${}^1{S}_0$ energy gap of ${\Sigma }^{-}$ hyperons in $\beta$-stable neutron star matter. We solve the BCS gap equation for an effective ${\Sigma }^{-}{\Sigma }^{-}$ pairing interaction derived from the most recent parametrization of the hyperon-hyperon interaction constructed by the Nijmegen group. We find that the ${\Sigma }^{-}$ hyperons are in a ${}^1{S}_0$ superfluid state in the density region $\sim 0.27-0.7$ fm${}^{-3}$, with a maximum energy gap of order 8 MeV at a total baryon number density of $\sim 0.37$ fm${}^{-3}$ and a ${\Sigma }^{-}$ fraction of about 8%. We examine the implications on neutron star cooling.

Comments: 4 pages, double column, 4 figures. Accepted in PRC