Strange quark stars within proper time regularized (2+1)-flavor NJL model

TL;DR

This paper investigates the structure of strange quark stars using a modified NJL model with a new parameter, analyzing how different parameters affect star properties and matching recent astrophysical observations.

Contribution

Introduces a new free parameter in the NJL model and studies its impact on strange quark star structure, aligning theoretical models with recent observational data.

Findings

Larger alpha and smaller B lead to heavier, stiffer stars.

The heaviest star model agrees with recent mass and radius observations.

Model satisfies constraints from GW170817 tidal deformability.

Abstract

In this work we use the equation of state (EOS) of (2+1)-flavor Nambu-Jona-Lasinio (NJL) model to study the structure of the strange quark star. With a new free parameter $\alpha$, the Lagrangian is constructed by two parts, the original NJL Lagrangian and the Fierz transformation of it, as $\mathcal{L}=(1-\alpha)\mathcal{L}_{NJL}+\alpha\mathcal{L}_{Fierz}$. To determine the range of $\alpha$, we compare the binding energies in the 2-flavor and (2+1)-flavor cases. We also consider the constraints of chemical equilibrium and electric charge neutrality in the strange quark star and choose six representative EOSs with different $\alpha$ and $B$ (bag constant) to study their influence on the structure of the strange quark star. As a result, we find that a larger $\alpha$ and a smaller $B$ corresponds to a heavier star with a stiffer EOS. Furthermore, the heaviest strange quark star is in agreement with not only the recent mass observation of PSR J0740+6620 and the X-ray observations on radius measurements, but also the constraint on tidal deformability of GW170817.