2022ApJ...929...82M

Using the relativistic mean-field model with nonlinear couplings between the isoscalar and isovector mesons, we study the properties of isospin-asymmetric nuclear matter. Not only the vector mixing, ω_µω^µρ_νρ^ν, but also the quartic interaction due to the scalar mesons, σ²δ², is taken into account to investigate the density dependence of nuclear symmetry energy, E_sym, and the neutron star properties. It is found that the δ meson increases E_sym at high densities, whereas the σ-δ mixing makes E_sym soft above the saturation density. Furthermore, the δ meson and its mixing have a large influence on the radius and tidal deformability of a neutron star. In particular, the σ-δ mixing reduces the neutron star radius; thus, the present calculation can simultaneously reproduce the dimensionless tidal deformabilities of a canonical 1.4 M_☉ neutron star observed from the binary neutron star merger GW170817 and the compact binary coalescence GW190814.