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

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 ⊙ 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 2 QM ¼ 1=3. We find promising cases which meet the 2 M ⊙ criterion and are interesting for CCSN explosions. We show that the very simple CSS EOS is transferable into the wellknown 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 2 QM ¼ 1=3 can increase the maximum mass only if reconfinement is suppressed or if quark matter is absolutely stable.

Classifications of twin star solutions for a constant speed of sound parameterized equation of state

“…al. [49] did a parameter scan with an identical parametrization to the one used in our approach, but with c 2 s = 1/3. This leads to a much smaller area in parameter space containing twin star solutions with an even smaller parameter space containing stars with M > 2M , which is in accordance with [26,29].…”

A Systematic Analysis of Hybrid Stars Using a Hadronic Equation of State Suitable for Core-Collapse Supernovae

“…These calculations enable us to make further steps towards generating a new hybrid supernova EOS. In [8], we restrict an extended parameter scan using HS(DD2) EOS to a small region interesting for supernova simulations. We also address the problem of reconfinement and hyperons in our parameter scan and show its influence on the maximum mass.…”

Akmal-Pandharipande-Ravenhall equation of state for simulations of supernovae, neutron stars, and binary mergers

“…In the APR formalism, this phase transition is taken into account by including extra potential terms in the high density phase (HDP) compared to the low density phase (LDP); see Eqs. (12) and (13). The extra terms in the HDP soften the EOS at high densities and cause a discontinuity in the pressure and chemical potentials of the EOS of APR.…”

“…For simplicity, we choose to work solely with nucleons, nuclei, electrons, positrons, and photons in this work. Extensions to include muons and antimuons [10], hyperons [11], and efforts to include quarks [12][13][14] also exist. We consider charge neutral matter in which the number density of electrons matches that of protons and positrons.…”