Strange quark matter and proto-strange stars in a baryon density-dependent quark mass model * *Supported by the National Natural Science Foundation of China (11875052, 11575190, 11135011)

Abstract

The properties of strange quark matter and the structures of (proto-)strange stars are studied within the framework of a baryon density-dependent quark mass model, where a novel quark mass scaling and self-consistent thermodynamic treatment are adopted. Our results indicate that the perturbative interaction has a significant impact on the properties of strange quark matter. It is determined that the energy per baryon increases with temperature, while the free energy decreases and eventually becomes negative. At fixed temperatures, the pressure at the minimum free energy per baryon is zero, suggesting that the thermodynamic self-consistency is preserved. Furthermore, the sound velocity v in quark matter approaches the extreme relativistic limit ( ) as the density increases. By increasing the strengths of the confinement parameter D and perturbation parameter C, the tendency for v to approach the extreme relativistic limit at high density is slightly weakened. For (proto-)strange stars, the novel quark mass scaling can accommodate massive proto-strange stars with their maximum mass surpassing twice the solar mass by considering the isentropic stages along the star evolution line, where the entropy per baryon of the star matter is set to be 0.5 and 1 with the lepton fraction = 0.4.