An extended equation of state for core-collapse simulations

TL;DR

This paper introduces an improved equation of state for stellar core-collapse simulations that includes pions and hyperons, significantly affecting thermodynamic properties during black hole formation.

Contribution

It develops an extended equation of state incorporating pions and hyperons, and tests its impact on core-collapse and black hole formation simulations.

Findings

Pions and hyperons influence pressure and internal energy significantly.

The extended EOS affects sound speed and thermodynamics in collapse regimes.

Simulations show notable differences in collapse dynamics with new particles.

Abstract

In stellar core-collapse events matter is heated and compressed to densities above nuclear matter saturation density. For progenitors stars with masses above about 25 solar masses, which eventually form a black hole, the temperatures and densities reached during the collapse are so high that a traditional description in terms of electrons, nuclei, and nucleons is no longer adequate. We present here an improved equation of state which contains in addition pions and hyperons. They become abundant in the high temperature and density regime. We study the different constraints on such an equation of state, coming from both hyperonic data and observations of neutron star properties. In order to test the zero-temperature versions, we perform numerical simulations of the collapse of a neutron star with such additional particles to a black hole. We discuss the influence of the additional particles on the thermodynamic properties within the hot versions of the equation of state and we show that in regimes relevant to core-collapse and black hole formation, the effects of pions and hyperons on pressure, internal energy and sound speed are not negligible.