Properties of quark matter and quark stars at zero temperature or under strong magnetic fields within MIT bag model

In this work, we investigate the properties of the strange quark matter (SQM) and the color-flavor-locked (CFL) quark matter at zero temperature or under strong magnetic fields within MIT bag model. We find the thermodynamical properties of CFL quark matter is strongly influenced by the pairing energy gap △ and the magnetic field. The sound velocity of CFL quark matter and the tidal deformability of CFL quark stars both increase with △, while the central baryon density of the maximum star mass in CFL state decreasing with △. Especially, the equation of state (EOS) of the CFL quark matter becomes stiffer with the increment of △, and the pressure becomes anisotropic when considering the magnetic fields in CFL quark matter. Our results indicate that the mass-radius lines of the CFL quark matter within MIT bag model can describe the recent observations of pulsars, and the maximum star mass of CFL quark matter increases with △. Moreover, the results indicate that the star mass of CFL quark matter depends on the magnetic field strength and orientation distributions inside the magnetars, and the polytropic index of CFL quark matter decreases with the star mass.