Studies of the structure of massive hybrid stars within a modified NJL model

TL;DR

This study investigates the structure of massive hybrid stars using a modified NJL model for quark matter and compares it with relativistic mean-field models for hadronic matter, finding stable stars with masses close to two solar masses and potential pure quark cores.

Contribution

It introduces a modified NJL model for quark matter in hybrid stars and compares hybrid EOSs with RMF models, highlighting the possibility of pure quark cores in massive stars.

Findings

Hybrid stars can reach nearly two solar masses.

Stable hybrid stars may have pure quark cores.

Hybrid EOSs are relatively soft but produce similar maximum masses.

Abstract

In this paper, we use the equation of state based on a modification of 2+1 flavors Nambu-Jona- Lasinio (NJL) model to study the quark matter of hybrid stars. For comparison, we utilize five EOSs of the relativistic mean-field (RMF) model to describe the hadronic phase. With the 3- window crossover interpolation approach, we try to construct relatively soft hybrid EOSs but find the maximum masses of hybrid stars do not differ too much. The results are quite close to two solar mass, which is consistent with the mass constraint of PSR J0348+0432. Furthermore it is noteworthy that the heaviest stable stars have central densities higher than that of the deconfinement transition thus suggesting a pure quark core in the hybrid star.