Speaker
Description
Hybrid neutron stars offer a promising platform to investigate the possible emergence of deconfined quark matter at supersaturation densities. The hadron-to-quark phase transition within hybrid neutron stars is commonly described by the Gibbs and Maxwell constructions of the equation of state. The two prescriptions respectively correspond to the limiting cases of vanishing and very large quark–hadron interface tension. Since the interface tension is poorly constrained, realistic hybrid matter may lie between these limits. We therefore employ a recently proposed interpolation framework based on the local-to-total electron ratio $\eta$, which continuously connects the Gibbs limit $\eta=0$ with global charge neutrality to the Maxwell limit $\eta=1$ with local charge neutrality. The hadronic phase is described by the Zhao--Lattimer parametrization and the quark phase by a three-flavor Nambu--Jona-Lasinio model with a repulsive vector interaction parametrized by the ratio $\xi = G_V/G_S$, where $G_V$ and $G_S$ represent the coupling constants in the vector and scalar interaction channels respectively. In addition to the stiffening of the mixed phase, we find that increasing $\xi$ at fixed $\eta$ further stiffens the quark branch. The combined effect increases the maximum mass from about $1.89\,M_\odot$ in the Gibbs limit without vector interaction ($\eta=0$, $\xi=0$) to approximately $2.28\,M_\odot$ near the Maxwell limit with the strongest vector coupling considered ($\eta=1$, $\xi=0.75$). The corresponding radii remain confined to a comparatively narrow range of $11.0$--$11.7$~km indicating that the mixed-phase treatment has a stronger influence on the maximum supported mass than on the stellar radius.