Study of nonstrange quark stars within a modified NJL model

In this work, a modified Nambu-Jona-Lasinio (NJL) model with proper-time regularization is employed to study the structure of nonstrange quark stars. The coupling constant four-fermion interaction in conventional NJL as $G=G_1+G_2\langle\bar{\psi}\psi\rangle$ highlight feedback propagator gluon propagator. To dependence equation state (EOS) on modification well vacuum pressure, we choose nine representative EOSs for comparison. It found that smaller $G_1$ leads stiffer EOS, and higher pressure (i.e., bag constant) yields softer EOS at low energy density. further shown heaviest star under satisfies not only recent mass measurement PSR J0740+6620, but also radius constraints from X-ray timing observations. corresponding tidal deformability agreement observations GW170817.