CORE-COLLAPSE SUPERNOVA EQUATIONS OF STATE BASED ON NEUTRON STAR OBSERVATIONS

TLDR

Current core‑collapse supernova equations of state predict neutron‑star radii that are too large and maximum masses that are too small, conflicting with recent observations, and they inadequately explore the nuclear symmetry energy. This work introduces two new equations of state that align with recent neutron‑star measurements and allow systematic study of nuclear‑matter property dependencies. The EOS tables span wide ranges of density, temperature, and asymmetry and are incorporated into a spherically symmetric, general‑relativistic radiation‑hydrodynamics supernova model with three‑flavor Boltzmann neutrino transport, then compared to standard EOS for 15‑ and 40‑solar‑mass progenitors. Simulations reveal no straightforward link between individual saturation‑density nuclear properties and supernova outcomes, but the new EOS yield the most compact neutron stars among relativistic mean‑field models and preserve the observed correlation between black‑hole formation time and the maximum mass of an s = 4 neutron star.

Abstract

Many of the currently available equations of state for core-collapse supernova simulations give large neutron star radii and do not provide large enough neutron star masses, both of which are inconsistent with some recent neutron star observations. In addition, one of the critical uncertainties in the nucleon-nucleon interaction, the nuclear symmetry energy, is not fully explored by the currently available equations of state. In this article, we construct two new equations of state which match recent neutron star observations and provide more flexibility in studying the dependence on nuclear matter properties. The equations of state are also provided in tabular form, covering a wide range in density, temperature and asymmetry, suitable for astrophysical simulations. These new equations of state are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. The results are compared with commonly used equations of state in supernova simulations of 15 and 40 solar mass progenitors. We do not find any simple correlations between individual nuclear matter properties at saturation and the outcome of these simulations. However, the new equations of state lead to the most compact neutron stars among the relativistic mean-field models which we considered. The new models also obey the previously observed correlation between the time to black hole formation and the maximum mass of an s=4 neutron star.