Massive neutron star with strangeness in a relativistic mean-field model with a high-density cutoff

The properties of neutron stars with the strangeness degree of freedom are studied in the relativistic mean-field (RMF) model via including a logarithmic interaction as a function of the scalar meson field. This interaction, named the $\sigma$-cut potential, can largely reduce the attractive contributions of the scalar meson field at high density without any influence on the properties of nuclear structure around the normal saturation density. In this work, the TM1 parameter set is chosen as the RMF interaction, while the strengths of $\sigma$-cut potential are constrained by the properties of finite nuclei so that we can obtain a reasonable effective nucleon-nucleon interaction. The hyperons $\mathrm{\Lambda },\mathrm{\Sigma }$, and $\mathrm{\Xi }$ are considered in neutron stars within this framework, whose coupling constants with mesons are determined by the latest hyperon-nucleon and $\mathrm{\Lambda }-\mathrm{\Lambda }$ potentials extracted from the available experimental data of hypernuclei. The maximum mass of neutron star can be larger than $2M_{\odot }$ with these hyperons in the present framework. Furthermore, the nucleon mass at high density will be saturated due to this additional $\sigma$-cut potential, which is consistent with the conclusions obtained by other calculations such as Brueckner-Hartree-Fock theory and quark mean-field model.

Figure 1

The effective nucleon masses in symmetric nuclear matter as functions of density with the original TM1 and the $\sigma$-cut potentials with $f_s=0.55$ and 0.60.

Figure 2

The binding energies per nucleon as functions of density for symmetric nuclear matter (a) and for pure neutron matter (b) with the original TM1 and the $\sigma$-cut potentials with $f_s=0.55$ and 0.60.

Figure 3

The symmetry energies per nucleon as functions of density with the original TM1 and the $\sigma$-cut potentials with $f_s=0.55$ and 0.60.

Figure 4

The pressures as functions of energy density with different $\sigma$-cut potentials in neutron stars including hyperons and without hyperons and $\sigma$-cut potential. “Y” in parentheses means the results including hyperons.

Figure 5

(a) The mass-radius relation and (b) mass-density relation for neutron star with the original TM1 (with and without hyperons) and the $\sigma$-cut potentials at $f_s=0.55$ and 0.60. “Y” in parentheses means the results including hyperons.

Figure 6

The particle fractions in neutron star with the original TM1 and the $\sigma$-cut potentials with $f_s=0.55$ and 0.60.