Constraints On Properties Of The Neutron Star And Equation Of State From Astronomical Observations

With more and more observations about neutron star,scientists have made great progress on the constraints of neutron star EOS and properties.In this thesis,we use the data from the merged binary neutron star GW 170817 event released by LIGO collaboration and observation data of the NICER collaboration to constrain properties of the neutron star.Based on the distribution of tidal deformabilities and component masses of binary neutron star merger GW170817,the isospin-dependent parametric equation of state(EOS)is employed to probe the nuclear symmetry energy Esym at twice saturation density and the properties of the neutron star,especially for the canonical neutron star.To obtain a proper distribution of the parameters of the EOS that is consistent with the observation,Bayesian analysis is used and the constraints of causality and maximum mass are considered.From this analysis,it is found that the symmetry energy and pressure at twice the saturation density of nuclear matter can be constrained within Esym(2?0)=34.5-2.3+20.5 MeV and P(2?0)=3.81-2.32+1.18×1034 dyn cm-2 at 90%credible level,respectively.Moreover,the constraints on the radii and dimensionless tidal deformabilities of canonical neutron stars are also demonstrated through this analysis,and the corresponding constraints are R1.4=12.60-1.80+0.60km and ?1.4=500-367+186at 90%credible level,respectively.With respect to the prior,our result(posterior result)prefers a softer EOS,corresponding to a lower expected value of symmetry energy,a smaller stellar radius,and a smaller tidal deformability.The Neutron Star Interior Composition Explorer(NICER)recently simultaneously measured the gravitational mass(Mg)and radius(R)of the isolated neutron star PSR J0030+0451.Inspired by the groundbreaking observation,we establish two new universal relations related to Mg and R to infer the gravitational binding energy(Eg)and moment of inertia(?)of PSR J0030+0451.By combining these new universal relations with the data of(Mg,R)released by NICER collaboration,the gravitational binding energy and moment of inertia of PSR J0030+0451 can be constrained within |Eg|=0.21-0.003+0.03 M? and I=1.95-0.50+0.70× 1045g cm2 at 68%credible level,respectively.