Astrophysical constraints on nuclear EOSs and coupling constants in relativistic-mean-field models

Utilizing various astrophysical constraints on neutron-star structures, we carry out a Bayesian analysis of the density-dependent behaviors of coupling constants in relativistic-mean-field (RMF) models as well as the nuclear matter properties at supranuclear densities. The effective nucleon interactions in the isoscalar-scalar, isoscalar-vector, and isovector-vector channels are considered, where the corresponding coupling constants (${\ensuremath{\alpha}}_{S},{\ensuremath{\alpha}}_{V},{\ensuremath{\alpha}}_{TV}$) are fixed by dividing the entire density range into three regions with six independent parameters. In this work, we focus on constraining the density-dependent point-coupling constants at supranuclear densities, while the coupling constants at subsaturation densities are derived from the covariant density functional DD-ME2. For those consistent with astrophysical observations, the coupling constants generally decrease with density and approach small positive values at large enough densities, which qualitatively agrees with various RMF models. The posterior probability density functions and their correlations of the coupling constants and various nuclear matter properties are examined as well. At the $1\ensuremath{\sigma}$ level, the constrained coupling constants at density $1.5{n}_{0}$ ($2.5{n}_{0}$) are ${\ensuremath{\alpha}}_{S}={3.1}_{\ensuremath{-}0.05}^{+0.1}(1.5{5}_{\ensuremath{-}0.2}^{+0.85})\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0ex}{0ex}}{10}^{\ensuremath{-}4}\text{ }\text{ }{\mathrm{MeV}}^{\ensuremath{-}2}$, ${\ensuremath{\alpha}}_{V}={2.3}_{\ensuremath{-}0.0}^{+0.1}({1.3}_{\ensuremath{-}0.1}^{+0.55})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }{\mathrm{MeV}}^{\ensuremath{-}2}$, and ${\ensuremath{\alpha}}_{TV}=2.0{5}_{\ensuremath{-}0.4}^{+0}(2.0{5}_{\ensuremath{-}0.5}^{+0})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{MeV}}^{\ensuremath{-}2}$. At larger densities, we find the lower limit of ${\ensuremath{\alpha}}_{TV}$ is not well constrained, so that more extensive calculations with a larger number of free parameters are necessary. Finally, the constrained pressure of neutron-star matter and symmetry energy of nuclear matter at $1.5{n}_{0}$ ($2.5{n}_{0}$) are $P=1{0}_{\ensuremath{-}0.0}^{+0.0}$ $({60}_{\ensuremath{-}20}^{+15})\text{ }\text{ }\mathrm{MeV}/{\mathrm{fm}}^{3}$ and ${\ensuremath{\epsilon}}_{\mathrm{sym}}=4{5}_{\ensuremath{-}3.0}^{+1.0}$ $({60}_{\ensuremath{-}6.0}^{+8.0})\text{ }\mathrm{MeV}$, respectively.