Bayesian inference of the crust–core transition density via the neutron-star radius and neutron-skin thickness data

In this work,we perform a Bayesian inference of the crust-core transition density ρ_(t) of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method.Uniform and Gaussian distributions for the ρ_(t) prior were adopted in the Bayesian approach.It has a larger probability of having values higher than 0.1 fm^(−3) for ρ_(t) as the uniform prior and neutron-star radius data were used.This was found to be controlled by the curvature K_(sym) of the nuclear symmetry energy.This phenomenon did not occur if K_(sym) was not extremely negative,namely,K_(sym)>−200 MeV.The value ofρ_(t) obtained was 0.075_(−0.01)^(+0.005) fm^(−3) at a confidence level of 68%when both the neutron-star radius and neutron-skin thickness data were considered.Strong anti-correlations were observed between ρ_(t),slope L,and curvature of the nuclear symmetry energy.The dependence of the three L-K_(sym) correlations predicted in the literature on crust-core density and pressure was quantitatively investigated.The most probable value of 0.08 fm^(−3) for ρ_(t) was obtained from the L-K_(sym) relationship proposed by Holt et al.while larger values were preferred for the other two relationships.

Transition density of the large mass hyperon star

The difference between the transition density of a larger mass hyperon star （for example, the neutron star PSR J1614-2230） and that of a smaller mass hyperon star is investigated in the framework of the relativistic mean field theory. We see that the transition density p0H increases with the increase of xw （i.e. the mass of the neutron star）. For the nucleons parts, the neutrons make the main contribution to the transition density as the baryon density P=p0H. With the increase of the xw （i.e. the mass of the neutron star）, the relative particle number density of neutrons decreases while that of protons increases. For the parts of hyperons, the ∧ and ≡. make the main contributions to the transition density as the baryon density p=p0H. The relative particle number density of A decreases while that of ≡ increases with the increase of the xw （i.e. the mass of the neutron star）. For the hyperons ∑-, ∑0 and E-, the total contributions are less than 16 per cent.

Stability of Quark Star Models

In this paper,we investigate the stability of quark stars with four different types of inner matter configurations;isotropic,charged isotropic,anisotropic and charged anisotropic by using the concept of cracking.For this purpose,we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the model.We conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.