Structures of the strange quark stars within a quasiparticle model

Abstract

The structures of strange quark stars are studied within a quasiparticle model obtained by the two-loop approximation. A softer equation of state yields a smaller maximum mass, a smaller radius, and makes the surface energy density and the surface quark chemical potential larger. The parameter space is obtained under the following constraints: the maximum mass of the strange quark star should be larger than 2.0 solar masses, which matches the masses of PSR $\mathrm{J}0348+0432$ and PSR $\mathrm{J}1614\text{\ensuremath{-}}2230$, and the surface energy density should be larger than $2.80\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }\mathrm{g}/{\mathrm{cm}}^{3}$. In our parameter space, the surface quark chemical potential is smaller than 308 MeV which is the critical quark chemical potential in QCD without electromagnetism. Also, the tidal Love number ${k}_{2}$ and deformability $\mathrm{\ensuremath{\Lambda}}$ are calculated for a 1.4-solar-mass strange quark star. A softer equation of state yields a smaller $\mathrm{\ensuremath{\Lambda}}(1.4)$ and leads to a strange quark star that is more compact and less likely to be tidally deformed. The data of GW170817 indicate that the upper bound of $\mathrm{\ensuremath{\Lambda}}(1.4)$ is 800 for the low-spin prior, which gives an upper bound of the parameter $\ensuremath{\zeta}$ of the running coupling constant ${\ensuremath{\alpha}}_{s}$ and gives a lower bound of the vacuum pressure density $B$, i.e., $\ensuremath{\zeta}l0.098\text{ }\text{ }\mathrm{GeV}$, $Bg(0.111\text{ }\text{ }\mathrm{GeV}{)}^{4}$. Moreover, the constraint on $\ensuremath{\zeta}$ also plays an important role in phenomenological studies of the quark-gluon plasma.