Mass–radius relation of neutron stars and massive pulsars with realistic equation of state

Abstract

Abstract We use up-to-date constraints on the mass and radius of 15 neutron star objects and pulsars, from electromagnetic and gravitational wave observables and different theoretical schemes, to extend the nuclear equation of state (EOS) based on realistic Michigan-three-Yukawa (M3Y) nucleon–nucleon interaction, which truly accounts for the low-density EOS of nuclear matter (NM), to describe dense NM. The considered EOSs are employed to map the mass–radius profiles using the Tolman–Oppenheimer–Volkoff equations of hydrostatic equilibrium. We found that the EOSs from CDM3Y-230 to CDM3Y-270, with saturation incompressibility K 0 = 230–270 MeV, successfully reproduce most of the recent constraints on the NS masses and radii. Based on both M3Y-Paris and M3Y-Reid NN interactions, these EOSs indicate radius of 11.67 ± 0.34 km for the NS of 1.4 M ʘ mass, and the expected maximum NS mass (M max) to be 1.93 ± 0.21 M ʘ. The upper limits of constraints indicated stiffer EOSs of K 0 = 300–330 MeV, which have estimated 1arger radii of 12.29 ± 0.14 km for NS (1.4 M ʘ) and heavier M max of 2.31 ± 0.14 M ʘ. Increasing the stiffness of the employed EOS is found to increase the indicated maximum mass of NS, its radius and maximum compactness, the core–crust transition density, the speed of sound in its interior, and slightly the transition proton-fraction, but to decrease the abundance of the proton, muon, and electron over npeμ core matter of NS, as well as the estimated central density.