Strong Hyperon-Nucleon Pairing in Neutron Stars

We explore the possibilities of hyperon-nucleon pairing, involving $\Lambda$ or ${\Sigma }^{-}$ hyperons, using different Nijmegen hyperon-nucleon potentials. We find possible very large $n{\Sigma }^{-}$ gaps and estimate their relevance for neutron star physics.

Figure 1

The different hyperon-nucleon gaps in symmetric matter. The numbers near the curves denote the NSC89 (0) or the NSC97a-f (1–6) potentials.

Figure 2

The $n{\Sigma }^{-}$ ${}^{3}S{D}_1$ gap with the NSC89 potential in asymmetric matter as a function of asymmetry for different total densities. The numbers above the curves indicate the value of $k_F=(3{\pi }^2{\rho }_{n\Sigma }/2{)}^{1/3}$ (in ${\mathrm{fm}}^{-1}$). The inset shows the maximum asymmetry as a function of $k_F$ (solid line labeled 0) together with the estimate Eq. (8) (dashed line) for the NSC89 and the NSC97f potential (solid line labeled 6).

Figure 3

Baryon fractions in beta-stable matter (a); corresponding total $n+{\Sigma }^{-}$ density (b) and asymmetry (c); resulting $n{\Sigma }^{-}$ ${}^{3}S{D}_1$ gap with the NSC89 potential (d); nucleonic ${}^{3}P{F}_2$ BCS gaps with the $V_{18}$ potential (e).