Towards generating a new supernova equation of state: A systematic analysis of cold hybrid stars

TL;DR

This paper systematically analyzes cold hybrid stars to develop a new supernova equation of state that supports 2 solar mass neutron stars and explores phase transition properties, hyperons, and quark matter models.

Contribution

It introduces a new hybrid supernova EOS compatible with observations by scanning phase transition parameters and analyzing hyperons and reconfinement effects.

Findings

Identified parameter sets supporting 2 M$_\\odot$ neutron stars.

Demonstrated transferability of CSS EOS into the thermodynamic bag model.

Found quark matter can increase maximum mass under certain conditions.

Abstract

The hadron-quark phase transition in core-collapse supernovae (CCSNe) has the potential to trigger explosions in otherwise nonexploding models. However, those hybrid supernova equations of state (EOS) shown to trigger an explosion do not support the observational 2 M$_\odot$ neutron star maximum mass constraint. In this work, we analyze cold hybrid stars by the means of a systematic parameter scan for the phase transition properties, with the aim to develop a new hybrid supernova EOS. The hadronic phase is described with the state-of-the-art supernova EOS HS(DD2), and quark matter by an EOS with a constant speed of sound (CSS) of $c_{QM}^2=1/3$. We find promising cases which meet the 2 M$_\odot$ criterion and are interesting for CCSN explosions. We show that the very simple CSS EOS is transferable into the well-known thermodynamic bag model, important for future application in CCSN simulations. In the second part, the occurrence of reconfinement and multiple phase transitions is discussed. In the last part, the influence of hyperons in our parameter scan is studied. Including hyperons no change in the general behavior is found, except for overall lower maximum masses. In both cases (with and without hyperons) we find that quark matter with $c_{QM}^2=1/3$ can increase the maximum mass only if reconfinement is suppressed or if quark matter is absolutely stable.