NEW HYPERON EQUATIONS OF STATE FOR SUPERNOVAE AND NEUTRON STARS IN DENSITY-DEPENDENT HADRON FIELD THEORY

Abstract

We develop new hyperon equation of state (EoS) tables for core-collapse\nsupernova simulations and neutron stars. These EoS tables are based on a\ndensity-dependent relativistic hadron field theory where baryon-baryon\ninteraction is mediated by mesons, using the parameter set DD2 from Typel et\nal. (2010) for nucleons. Furthermore, light and heavy nuclei along with the\ninteracting nucleons are treated in the nuclear statistical equilibrium model\nof Hempel and Schaffner-Bielich which includes excluded volume effects. Of all\npossible hyperons, we consider only the contribution of $\\Lambda$s. We have\ndeveloped two variants of hyperonic EoS tables: in the np$\\Lambda \\phi$ case\nthe repulsive hyperon-hyperon interaction mediated by the strange $\\phi$ meson\nis taken into account, and in the np$\\Lambda$ case it is not. The EoS tables\nfor the two cases encompass wide range of density ($10^{-12}$ to $\\sim$ 1\nfm$^{-3}$), temperature (0.1 to 158.48 MeV), and proton fraction (0.01 to\n0.60). The effects of $\\Lambda$ hyperons on thermodynamic quantities such as\nfree energy per baryon, pressure, or entropy per baryon are investigated and\nfound to be significant at high densities. The cold, $\\beta$-equilibrated EoS\n(with the crust included self-consistently) results in a 2.1 M$_{\\odot}$\nmaximum mass neutron star for the np$\\Lambda \\phi$ case, whereas that for the\nnp$\\Lambda$ case is 1.95 M$_{\\odot}$. The np$\\Lambda \\phi$ EoS represents the\nfirst supernova EoS table involving hyperons that is directly compatible with\nthe recently measured 2 M$_{\\odot}$ neutron stars.\n