Hyperons in hot dense matter: what do the constraints tell us for equation of state?

TL;DR

This paper develops new equations of state including hyperons for hot dense matter, consistent with nuclear physics constraints, and explores their implications for neutron star properties and astrophysical phenomena.

Contribution

The authors introduce two new hyperonic equations of state compatible with constraints and compare them with existing models, highlighting the impact of symmetry energy on dense matter.

Findings

New hyperonic EoS models satisfy 2 solar mass neutron star constraint.

Differences in symmetry energy affect strangeness content and thermodynamics.

Predictions influence neutron star merger and protoneutron star evolution.

Abstract

For core-collapse and neutron star merger simulations it is important to have at hand adequate equations of state, describing the underlying dense and hot matter as realistically as possible. Here, we present two newly constructed equation of state (EoS) including the entire baryon octet. Both EoS are compatible with the main constraints from nuclear physics, both experimental and theoretical. One of the EoS is equally describing maximum mass for cold $\beta$-equilibrated neutron stars of $2 M_\odot$ in agreement with recent observations. The predictions obtained with the new EoS are compared with the results obtained with DD2Y, the only presently existing EoS containing the baryon octet, that satisfies the same constraints within uncertainties. The main difference between our new EoS models and DD2Y is the harder symmetry energy of the latter. We show that the density dependence of the symmetry energy has a direct influence on the amount of strangeness inside hot and dense matter and consequently on thermodynamic quantities, e.g. the temperature for given entropy per baryon. We expect these differences to affect the evolution of a protoneutron star or binary neutron star mergers. We also propose several parametrizations calibrated to $\Lambda$ hypernuclei based on the DD2 and SFHo models that satisfy the two solar mass constraint.