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.
Highlights
The equation of state (EOS) plays a critical role in the study of the neutron star
The nonstrange quark star has been studied for the two-flavor case [13,14], and the results satisfy both the two solar mass constraint from PSR J0348 þ 0432 [2] and the tidal deformability constraint Λð1.4 M⊙Þ ≤ 800 from GW170817 in the previous study [6]
II, we introduce the EOS of the strange quark star with the modified (2 þ 1)-flavor NJL model
Summary
The equation of state (EOS) plays a critical role in the study of the neutron star. Substituting an EOS into the Tolman-Oppenheimer-Volkoff (TOV) equation, we can get the corresponding mass-radius relation of the star. In a recent study [44], the authors propose a modified NJL model containing both the original model Lagrangian and the Fierz transformation of it with the parameter (1 − α) and α adjusting the weight of these two parts, respectively, producing stiffer EOSs than before In this scheme, the nonstrange quark star has been studied for the two-flavor case [13,14], and the results satisfy both the two solar mass constraint from PSR J0348 þ 0432 [2] and the tidal deformability constraint Λð1.4 M⊙Þ ≤ 800 from GW170817 in the previous study [6]. The mass-radius relation and the tidal deformability of the strange quark star with the corresponding EOS are studied.
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