Equation of state and composition of proto-neutron stars and merger remnants with hyperons

Abstract

Finite-temperature equation of state (EoS) and the composition of dense nuclear and hypernuclear matter under conditions characteristic of neutron star binary merger remnants and supernovas are discussed. We consider both neutrino free-streaming and trapped regimes which are separated by a temperature of a few MeV. The formalism is based on covariant density functional (CDF) theory for the full baryon octet with density-dependent couplings, suitably adjusted in the hypernuclear sector. The softening of the EoS with the introduction of the hyperons is quantified under various conditions of lepton fractions and temperatures. We find that $\Lambda$, ${\Xi }^{-}$, and ${\Xi }^0$ hyperons appear in the given order with a sharp density increase at zero temperature at the threshold being replaced by an extended increment over a wide density range at high temperatures. The $\Lambda$ hyperon survives in the deep subnuclear regime. The triplet of $\Sigma$s is suppressed in cold hypernuclear matter up to around seven times the nuclear saturation density, but appears in significant fractions at higher temperatures, $T\ge 20$ MeV, in both supernova and merger remnant matter. We point out that a special isospin degeneracy point exists where the baryon abundances within each of the three isospin multiplets are equal to each other as a result of (approximate) isospin symmetry. At that point, the charge chemical potential of the system vanishes. We find that under the merger remnant conditions, the fractions of electron and $\mu$-on neutrinos are close and are about 1\%, whereas in the supernova case, we only find a significant fraction ($\sim$10\%) of electron neutrinos, given that in this case, the $\mu$-on lepton number is zero.

v2: 16 pages, 7 figure, minor clarifications, matches published version. v1: 17 pages, 6 figures, submitted to "Universe"

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Cited by in corpus (10)

• Heavy Baryons in Compact Stars
• Delta-resonances and hyperons in proto-neutron stars and merger remnants
• Exotic Baryons in Hot Neutron Stars
• Non-radial oscillations in newly born compact star considering effects of phase transition
• The impact of hyperons on neutron star mergers: gravitational waves, mass ejection and black hole formation
• Influence of the effective mass on the properties of nuclear matter at finite density and temperature
• $f$-mode oscillations in hot Neutron Stars: Effect of hyperons and neutrino trapping
• Simulating Binary Neutron Star Mergers with Finite-temperature Equations of State: The influences of the slope of the symmetry energy and artificial heating
• Modification of the universal relation between mass, radius and nonradial $f$-mode oscillation in proto-neutron stars
• Equation of state for hot hyperonic neutron star matter