In the present work, we systematically study the $\alpha$ decay preformation factors $P_{\alpha }$ within the cluster-formation model and $\alpha$ decay half-lives by the proximity potential 1977 formalism for nuclei around $Z=82,N=126$ closed shells. The calculations show that the realistic $P_{\alpha }$ is linearly dependent on the product of valance protons (holes) and valance neutrons (holes) $N_p{N}_n$. It is consistent with our previous works [Sun et al., Phys. Rev. C 94, 024338 (2016); Deng et al., Phys. Rev. C 96, 024318 (2017)], in which $P_{\alpha }$ are model dependent and extracted from the ratios of calculated $\alpha$ half-lives to experimental data. Combining with our previous works, we confirm that the valance proton-neutron interaction plays a key role in the $\alpha$ preformation for nuclei around $Z=82,N=126$ shell closures whether the $P_{\alpha }$ is model dependent or microcosmic. In addition, our calculated $\alpha$ decay half-lives by using the proximity potential 1977 formalism taking $P_{\alpha }$ evaluated by the cluster-formation model can well reproduce the experimental data and significantly reduce the errors.

Within a confining quark matter model which considers phenomenologically the quark confinement and asymptotic freedom as well as the chiral symmetry restoration and quark deconfinement at high baryon density, we find that if the up-down quark matter ($ud\mathrm{QM}$) is more stable than nuclear matter and strange quark matter (SQM), the maximum mass of static quark stars with $ud\mathrm{QM}$ is $2.87M_{\odot }$ under agreement with both the constraints on star tidal deformability from gravitational wave signal GW170817 and the mass-radius of PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+6620$ measured by NICER. In contrast, the conventional strange quark star with the SQM that is more stable than nuclear matter while the nuclear matter is more stable than $ud\mathrm{QM}$, has a maximum static mass of only $1.87M_{\odot }$ and its radius significantly deviates from NICER’s constraint. Our results thus provide circumstantial evidence suggesting the recently reported GW190814’s secondary component with a mass of ${2.59}_{-0.09}^{+0.08}{M}_{\odot }$ could be an up-down quark star.

We investigate the properties of asymmetric quark matter and strange quark matter in the framework of the SU(3) Nambu–Jona-Lasinio (NJL) model with two types of vector interactions: (1) the flavor-dependent repulsion among different flavors of quarks with the coupling constant $G_V$, and (2) the universal repulsion and the vector-isovector interaction among different flavors of quarks with the coupling constants $g_V$ and $G_{IV}$. Using these two types of vector interactions in the NJL model, we study the quark symmetry energy in asymmetric quark matter, the constituent quark mass, the quark fraction, the equation of state in strange quark matter, the maximum mass of a quark star, and the properties of the QCD phase diagram. We find that including the two types of vector interactions in the SU(3) NJL model can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. In particular, our results indicate that we can describe PSR $\mathrm{J}1614-2230$ and PSR $\mathrm{J}0348+0432$ as quark stars by considering the universal repulsion and the vector-isovector interaction among quark matter in the SU(3) NJL model.

We investigate the properties of the equation of state of strange-quark matter and $u\text{−}d$ quark matter, the sound velocity of quark matter, the stability region for star matter, the maximum mass of quark stars (QSs), and the tidal deformability for QSs by using a quark quasiparticle model. Our results indicate that the recently discovered heavy compact stars PSR $\mathrm{J}0348+0432$, MSR $\mathrm{J}0740+6620$, and PSR $\mathrm{J}2215+5135$, and especially the GW190814s secondary component $m_2$ can be well described as QSs within the quasiparticle model.

We extend the SU(3) Nambu–Jona-Lasinio (NJL) model to include two types of vector interaction. Using these two types of vector interaction in NJL mod

We study the thermodynamic properties of asymmetric quark matter, large mass quark stars (QSs), and proto-quark stars (PQSs) within the quasiparticle model. Considering the effects of temperature within quasiparticle model can significantly influence the EOS and the entropy of strange quark matter (SQM), quark fractions in SQM, as well as the tidal deformability and the maximum mass of PQSs along the star evolution line. Our results indicate that the recent discovered heavy compact stars PSR J0348+0432, MSR J0740+6620, PSR J2215+5135, and especially the GW190814’s secondary component $$m_2$$m 2 can be well described as QSs within the quasiparticle model. The tidal deformability for the QSs describing the heavy compact stars is extremely large, which can not well describe GW170817 as QSs, and the effects of the temperature in the heating process along the star evolution will further increase the tidal deformability and the maximum mass of PQSs.