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NEW HYPERON EQUATIONS OF STATE FOR SUPERNOVAE AND NEUTRON STARS IN DENSITY-DEPENDENT HADRON FIELD THEORY
Journal
Astrophysical journal. Supplement series
Volume
214
Number
2
Pages / Article-Number
22
Keywords
equation of state, stars: neutron, supernovae: general
Abstract
We develop new hyperon equation of state (EoS) tables for core-collapse supernova simulations and neutron stars. These EoS tables are based on a density-dependent relativistic hadron field theory where baryon-baryon interaction is mediated by mesons, using the parameter set DD2 for nucleons. Furthermore, light and heavy nuclei along with interacting nucleons are treated in the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich which includes excluded volume effects. Of all possible hyperons, we consider only the contribution Lambda s. We have developed two variants of hyperonic EoS tables: in the np Lambda phi case the repulsive hyperon-hyperon interaction mediated by the strange phi meson is taken into account, and in the np Lambda case it is not. The EoS tables for the two cases encompass a wide range of densities (10(-12) to similar to 1 fm(-3)), temperatures (0.1 to 158.48 MeV), and proton fractions (0.01 to 0.60). The effects of Lambda hyperons on thermodynamic quantities such as free energy per baryon, pressure, or entropy per baryon are investigated and found to be significant at higher densities. The cold, beta-equilibrated EoS (with the crust included self-consistently) results in a 2.1 M-circle dot maximum mass neutron star for the np Lambda phi case, whereas that for the np Lambda phi case is 1.95 M-circle dot. The np Lambda phi EoS represents the first supernova EoS table involving hyperons that is directly compatible with the recently measured 2 M-circle dot neutron stars.
