We investigate the effects of non-Newtonian gravity on the properties of strange quark stars (QSs) and constrain the parameters of the standard MIT bag model used to describe strange quark matter (SQM) by employing the mass of PSR J0740+6620 and the tidal deformability of GW170817. We find that, for the standard MIT bag model, these mass and tidal deformability observations would rule out the existence of QSs if non-Newtonian gravity effects are ignored. For a strange quark mass of m s  = 95 MeV, we find that QSs can exist for values of the non-Newtonian gravity parameter g 2/μ 2 in the range of 1.37 GeV−2 ≤ g 2/μ 2 ≤ 7.28 GeV−2 and limits on the bag constant and the strong interaction coupling constant of the SQM model given by 141.3 MeV ≤ B 1/4 ≤ 150.9 MeV and α S  ≤ 0.56. For a strange quark mass of m s  = 150 MeV, QSs can exist for 1.88 GeV−2 ≤ g 2/μ 2 ≤ 6.27 GeV−2 and limits on the parameters of the SQM model given by 139.7 MeV ≤ B 1/4 ≤ 147.3 MeV and α S  ≤ 0.49.

No abstract

We proposed alternative explanation to the rapid cooling of neutron star in Cas A. It is suggested that the star is experiencing the recovery period following the r -mode heating process, assuming the star is differentially rotating. Like the neutron-superfluidity-triggering model, our model predicts the rapid cooling will continue for several decades. However, the behavior of the two models has slight differences, and they might be distinguished by observations in the near future.

We investigate the influence of nucleon superfluidity on the neutrino emissivity of nonequilibrium β processes. Calculations of the reduction factors for direct and modified Urca processes with three types of nucleon superfluidity in npe matter are performed. The numerical results are given because the analytical solution is impossible. We find that the superfluid influence is closely related to the chemical departure from β equilibrium. For a small chemical departure, the superfluid reduction factor depends almost only on the gap and is hardly affected by the departure, while for a large enough departure, it rapidly enhances neutrino emissivity. The onset of "enchanced" emission has some corresponding thresholds that seem to be linked to the ratio of the energy gap to the chemical departure.

No abstract