Equations of state for hot neutron stars -- II. The role of exotic particle degrees of freedom

TL;DR

This paper develops and analyzes equations of state for hot neutron stars, including exotic particles like hyperons, $$Delta resonances, and quarks, to understand their impact on astrophysical phenomena such as supernovae and neutron star mergers.

Contribution

It introduces new equations of state incorporating $$Delta(1232) resonances within covariant density functional theory and evaluates their stability and thermal properties under astrophysical conditions.

Findings

$$Delta resonances affect the stability of nuclear matter.

Exotic particles modify the thermal properties relevant for supernovae.

Comparison of models shows significant differences in thermodynamic behavior.

Abstract

Explosive astrophysical systems - such as supernovae or compact star binary mergers - provide conditions where exotic degrees of freedom can be populated. Within the covariant density functional theory of nuclear matter we build several general purpose equations of state which, in addition to the baryonic octet, account for $\Delta(1232)$ resonance states. The thermodynamic stability of $\Delta$-admixed nuclear matter is investigated in the limiting case of vanishing temperature for charge fractions $Y_Q=0.01$ and $Y_Q=0.5$ and wide ranges of the coupling constants to the scalar and vector mesonic fields. General purpose equation of state models with exotica presently available on the \textsc{CompOSE} database are further reviewed; for a selection of them we then investigate thermal properties for thermodynamic conditions relevant for core-collapse supernovae and binary neutron star mergers. Modifications induced by hyperons, $\Delta(1232)$, $K^-$, pions and quarks are discussed.