Narrow Results

We use a modified SU(2) chiral sigma model to study nuclear matter at high density using mean field approach. We also study the phase transition of nuclear matter to quark matter in the interior of highly dense neutron stars. Stable solutions of Tolman–Oppenheimer–Volkoff equations representing hybrid stars are obtained with a maximum mass of 1.69M_⊙, radii around 9.3 km and a quark matter core constituting nearly 55–85% of the star radii.

We use a modified SU(2) chiral sigma model to study nuclear matter component and simple bag model for quark matter constituting a neutron star. We also study the phase transition of nuclear matter to quark matter with the mixed phase characterized by two conserved charges in the interior of highly dense neutron stars. Stable solutions of Tolman–Oppenheimer–Volkoff equations representing hybrid stars are obtained with a maximum mass of 1.67M_⊙ and radius around 8.9 km.

The properties of hybrid stars are studied via the hybrid EOSs that are compatible with astrophysical observables. These hybrid EOSs are constructed by interpolating between hadronic EOS at lower densities and the quark EOS at higher densities. The BSR6 EOS derived from the RMF model is adopted as the hadronic EOS, while the quark EOS is calculated via a quasiparticle model. The maximum masses obtained from the hybrid EOSs are larger than $2M_{\odot }$, and the tidal deformabilities for $1.4M_{\odot }$ hybrid stars are smaller than 800. The combined tidal deformability $\tilde{\mathrm{\Lambda }}$ is a monotonically increasing function of mass ratio $\eta$ for both hybrid EOSs and hadronic EOS, and it depends weakly on $\eta$. The results of all hybrid EOSs can strictly satisfy the constraint of $70<\tilde{\mathrm{\Lambda }}<720$ and the mass and radius constraints from the newest joint analysis of NICER, XMM-Newton and GW170817 data.