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

Abstract

In this work, we use the equation of state (EOS) of the (2+1)-flavor Nambu-Jona-Lasinio (NJL) model to study the structure of the strange quark star. With a new free parameter α, the Lagrangian is constructed by two parts, the original NJL Lagrangian and the Fierz transformation of it, as L=(1-α)LNJL+αLFierz. To determine the range of α, we compare the binding energies in the two-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 α and B (bag constant) to study their influence on the structure of the strange quark star. As a result, we find that a larger α and a smaller B correspond 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 the tidal deformability of GW170817.