Hybrid stars can be self-bound

TL;DR

This paper demonstrates that hybrid stars can be self-bound objects, with their properties consistent with recent astronomical observations, by modeling their matter composition and equations of state.

Contribution

It introduces a novel finding that hybrid stars can be self-bound, contrasting with previous studies that considered them gravitationally bound.

Findings

Hybrid stars are composed of uniform hadronic matter on the surface.

The mass-radius relation and tidal deformability align with recent astronomical data.

Hybrid stars can be self-bound rather than gravitationally bound.

Abstract

Based on the properties of uniform nuclear matter at the nuclear saturation density and basic thermodynamic relations, we first re-study the composition of matter on the surface of normal neutron stars and hybrid stars. It is found that the hybrid stars are composed of uniform hadronic matter on the surface rather than heavy nuclei. Then we use the Walceka model and the self-consistent NJL model to describe the equation of state of low-density hadrons and quark matter at high densities respectively, and the P--interpolation method is employed to connect the equation of state at the extreme densities to study hybrid stars. As a result, we find that the obtained hybrid star mass-radius relation and tidal deformability meet the latest astronomical data. More importantly, we find that the hybrid stars we obtained can be self-bound rather than gravitationally bound, which is completely different from previous related studies.