GW170817 Constraint On Neutron-Star Equation Of State

Neutron star?NS?,one of the most compact forms for substances in the observable universe,remains irreplaceable laboratory to probe the secrets of the super-dense matters.From the perspectives of microphysics,the asymmetric nuclear matter?ANM?equation of state?EoS?governs most macroscopic properties of the NS.The astrophysical observations can therefore be inversely applied to constrain the EoS of the NS.The precise mass measurement of the two massive NSs,PSR J0348+0432 and PSR J1614-2230,imposed strong restriction on the maximum mass M_max of NS a while ago,eliminating a bulk of EoSs that are excessively soft.The recent gravitational wave detection,GW170817,which corresponds to the coalesce of a double neutron star system has provided valuable information on NS interior structure.The combined tidal polarizability which describes the deformation of the two NSs in the tidal field was constrained to ????800 by LIGO.This paper studies how the nuclear symmetric energy relates to the observable properties of a NS.The joint distributions of both the masses and the tidal deformabilities,inferred from GW170817,are then used to constrain the symmetric-energy parameters,under the frameworks of Bayesian analysis.Together with observational restriction on M_max,employing more than4×10⁶ samples of ANM EoS,the posterior distributions indicate that the canonical radius and the tidal deformability for an individual star with a mass of 1.4M_?are separately constrained to 11.2<R_1.4km<12.8 and 126<?_1.4<547.The statistical results strongly disfavor the EoSs that are excessively stiff.The most probable value for the posterior M_max is estimated as 2.10M_?.In addition to ANM EoS,the likelihood of several widely-used EoSs in NS investigation are also inspected under the same frameworks,including APR,SLy4,DBHF,WFF1,etc.In virtue of the great amount of generated EoS tables,this paper tests and demonstrates several EoS-insensitive relations among the moment of inertia,the tidal Love number and the stellar compactness.The best-fitted relations for ANM EoSs are provided.Based on massive instances,this paper also proposes a simple resolution standard to reduce the interpolation-induced errors in computing the NS structure,that is,the EoS tables should contain more than 50 points at the density segment?1,10? ?₀,where ?₀ refers to the nuclear saturation density.