Narrow Results

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.

The low density contribution to the tidal deformability and moment of inertia of a neutron star are calculated via various well known equations of state. The contributions to the moment of inertia are directly calculated, whilst the tidal deformability’s are constructed through comparing an equation of state with a fit with the low density region removed. With the recent measurement of GW170817 providing constraints on the tidal deformability, it is very important to understand what features of the equation of state have the biggest effect on it.