Study of the nuclear matter equation of state and neutron star properties based on latest nicer radius observations and chiral effective field theory results

In this work, we employ the equation of state (EOS) of neutron star core matter with explicit isospin dependence, combined with the latest neutron star radius observations and chiral effective field theory (EFT) constraints at low densities, to perform a Bayesian analysis of the EOS parameter uncertainties and their impact on neutron star macroscopic properties. The results indicate that the constraints on the symmetric nuclear matter parameters K_0 and J_0 remain relatively stable, while the uncertainties in the symmetry energy parameters L and K_mathrmsymare significantly reduced, yielding L = 58.0^+2.0-10.0MeV and K_mathrmsym= -156.0^+24.0-60.0MeV at the 90% credible level. The symmetry energy at twice saturation density is further constrained within 39.5–49.5 MeV. These results suggest that chiral EFT plays a dominant role at low densities, whereas neutron star observations primarily constrain the high-density behavior of the EOS.The macroscopic properties of neutron stars are also more tightly constrained. At the 90% credible level, the maximum mass is 2.20^+0.10-0.20M_ødot, which disfavors interpreting the secondary compact object in GW190814 as a neutron star. The radius difference Δ R = R_2.0- R_1.4is constrained to -0.27^+0.18-0.42km, indicating that the joint analysis of the latest neutron star observations and chiral EFT favors a relatively soft EOS. In contrast, analyses based solely on neutron star observations or chiral EFT results yield Δ R > 0, corresponding to a stiffer EOS.