Superfluidity of $\Lambda$ hyperons in neutron stars

TL;DR

This paper investigates the superfluidity of $ ext{Lambda}$ hyperons in neutron stars using relativistic mean field theory, examining how different interactions influence pairing gaps and the presence of superfluidity in neutron star cores.

Contribution

It introduces a detailed analysis of $ ext{Lambda}$ hyperon superfluidity in neutron stars considering updated hyperon potentials and various $ ext{Lambda} ext{Lambda}$ interactions, highlighting their impact on pairing gaps and superfluidity.

Findings

Maximal pairing gap is a few tenths of a MeV.

Superfluidity existence depends on the $ ext{Lambda} ext{Lambda}$ interaction used.

The density region of the pairing gap varies with interaction choice.

Abstract

We study the $^1S_0$ superfluidity of $\Lambda$ 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 $\Lambda$ hyperons, we employ several $\Lambda\Lambda$ interactions based on the Nijmegen models and used in double-$\Lambda$ 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 $\Lambda\Lambda$ interaction and the treatment of neutron star matter. We calculate neutron star properties and find that whether the $^1S_0 $ superfluidity of $\Lambda$ hyperons exists in the core of neutron stars mainly depends on the $\Lambda\Lambda$ interaction used.