Superfluidity of Λ hyperons in neutron stars

We study the 1S0 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 1S0 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 1S0 superfluidity of Λ hyperons exists in the core of neutron stars mainly depends on the ΛΛ interaction used.