A new equation of state for dense hydrogen-helium mixtures II: taking into account hydrogen-helium interactions

TL;DR

This paper extends a previous dense hydrogen-helium equation of state by incorporating hydrogen-helium interactions from quantum molecular dynamics, crucial for modeling brown dwarfs and giant planets.

Contribution

It introduces a new EOS that accounts for H/He interactions, improving accuracy over the additive volume law approach.

Findings

H/He interactions significantly affect the EOS at low temperatures and high densities.

The new EOS predicts phase separation phenomena in dense H/He mixtures.

Publicly available tables facilitate use in astrophysical modeling.

Abstract

In a recent paper (Chabrier et al. 2019), we have derived a new equation of state (EOS) for dense hydrogen/helium mixtures which covers the temperature-density domain from solar-type stars to brown dwarfs and gaseous planets. This EOS is based on the so-called additive volume law and thus does not take into account the interactions between the hydrogen and helium species. In the present paper, we go beyond these calculations by taking into account H/He interactions, derived from quantum molecular dynamics simulations. These interactions, which eventually lead to H/He phase separation, become important at low temperature and high density, in the domain of brown dwarfs and giant planets. The tables of this new EOS are made publicly available.