Subjects: Physics >> Nuclear Physics Subjects: Physics >> Geophysics, Astronomy, and Astrophysics submitted time 2024-01-09
Abstract： According to the recent studies, the gravitational wave (GW) echoes are expected to be generated by quark stars composed of ultrastif quark matter. The ultrastif equations of state (EOS) for quark matter were usually obtained either by a simple bag model with artifcially assigned sound velocity or by employing interacting strange quark matter (SQM) depicted by simple reparameterization and rescaling. In this study, we investigate GW echoes with EOSs for SQM in the framework of the equivparticle model with density-dependent quark masses and pairing efects. We conclude that strange quark stars (SQSs) can be sufciently compact to possess a photon sphere capable of generating GW echoes with frequencies in the range of approximately 20 kHz. However, SQSs cannot account for the observed 72 Hz signal in GW170817 event. Furthermore, we determined that quark-pairing efects play a crucial role in enabling SQSs to satisfy the necessary conditions for producing these types of echoes.
Subjects: Physics >> Nuclear Physics submitted time 2023-06-09 Cooperative journals: 《Nuclear Science and Techniques》
Abstract： Research performed during the past decade revealed an important role of symmetry energy in the equation of state (EOS) of strange quark matter (SQM). By introducing an isospin-dependent term into the quark mass scaling, the SQM stability window in the equivparticle model was studied. The results show that a sufficiently strong isospin dependence CI can significantly widen the SQM region of absolute stability, yielding results that simultaneously satisfy the constraints of the astrophysical observations of PSR J1614-2230 with 1:928 0:017 M and tidal deformability 70 1:4 580 measured in the event GW170817. With increasing CI , the difference between the u, d, and s quark fractions for the SQM in equilibrium becomes inconspicuous for C > 1, leading to small isospin asymmetry , and further resulting in similar EOS and structures of strange quark stars (SQSs). Moreover, unlike the behavior of the maximum mass of u–d QSs, which varies with CI depending on the sign of the parameter C, the maximum mass of the SQSs decreases monotonously with increasing CI .
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