Superfluidity of $Λ$ hyperons in neutron stars

Abstract

We study the $^1S_0$ superfluidity of $Λ$ hyperons in neutron star matter and neutron stars. We use the relativistic mean field (RMF) theory to calculate the properties of neutron star matter. In the RMF approach, the meson-hyperon couplings are constrained by reasonable hyperon potentials that include the updated information from recent developments in hypernuclear physics. To examine the $^1S_0$ pairing gap of $Λ$ hyperons, we employ several $ΛΛ$ interactions based on the Nijmegen models and used in double-$Λ$ hypernuclei studies. It is found that the maximal pairing gap obtained is a few tenths of a MeV. The magnitude and the density region of the pairing gap are dependent on the $ΛΛ$ interaction and the treatment of neutron star matter. We calculate neutron star properties and find that whether the $^1S_0 $ superfluidity of $Λ$ hyperons exists in the core of neutron stars mainly depends on the $ΛΛ$ interaction used.

22 pages, 2 Tables, 6 Figure