New Equations of State in Simulations of Core-Collapse Supernovae

Abstract

We discuss three new equations of state (EOS) in core-collapse supernova simulations. The new EOS are based on the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich (HS), which includes excluded volume effects and relativistic mean-field (RMF) interactions. We consider the RMF parameterizations TM1, TMA, and FSUgold. These EOS are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics and three-flavor Boltzmann neutrino transport. The results obtained for the new EOS are compared with the widely used EOS of H. Shen et al. and Lattimer & Swesty. The systematic comparison shows that the model description of inhomogeneous nuclear matter is as important as the parameterization of the nuclear interactions for the supernova dynamics and the neutrino signal. Furthermore, several new aspects of nuclear physics are investigated: the HS EOS contains distributions of nuclei, including nuclear shell effects. The appearance of light nuclei, e.g., deuterium and tritium is also explored, which can become as abundant as alphas and free protons. In addition, we investigate the black hole formation in failed core-collapse supernovae, which is mainly determined by the high-density EOS. We find that temperature effects lead to a systematically faster collapse for the non-relativistic LS EOS in comparison to the RMF EOS. We deduce a new correlation for the time until black hole formation, which allows to determine the maximum mass of proto-neutron stars, if the neutrino signal from such a failed supernova would be measured in the future. This would give a constraint for the nuclear EOS at finite entropy, complementary to observations of cold neutron stars.

Systematic features of axisymmetric neutrino-driven core-collapse supernova models in multiple progenitors

“…Here it should be noted that the above threshold is for a cold NS, whereas the PNS soon after bounce is still hot. At this phase, the contribution of thermal pressure to the maximum mass cannot be neglected, so that the maximum mass of the hot PNS is bigger than that of the cold NS (O'Connor & Ott 2011;Hempel et al 2012). Based on a systematic 1D GR simulation with approximate neutrino transport, O'Connor & Ott (2011) showed that the maximum gravitational mass of the hot PNSs, which is bigger for models with high compactness, ranges from 2.1M ⊙ (ξ 2.5,cb = 0.20) 2 to 2.5 M ⊙ (1.15).…”

The role of weak interactions in dynamic ejecta from binary neutron star mergers

“…In the rates calculations, we have included Pauli blocking factors for electrons and positrons in the final states, while we have neglected neutrino blocking factors in free streaming conditions. Hot and dense matter in NSE is described by a nuclear equation of state in tabular form (Hempel et al 2012). For consistency with the underlying simulation, we choose the NL3 parameterization for the nucleon interaction.…”

“…In all cases, we obtain a rather broad distribution of the electron fraction, with generally less neutron-deficient values, as we assume higher (anti)neutrino luminosities. The nucleosynthesis in the ejecta is sensitive to the electron fraction, Y e , the entropy, s, and the expansion time scale (or equivalently the expansion velocity, v 8GK ) at NSE freeze-out (e.g., Hoffman et al 1997). Using the whole ensemble of ejected tracers from the simulation, we obtain distributions for all these quantities, recorded when the tracer temperature drops below 8 GK, well after the shock has passed.…”

Composition of Nuclear Matter with Light Clusters and Bose–Einstein Condensation of $$\alpha $$ α Particles

“…The topics of current interest are, for example, the improvements on the supernova and warm neutron star equations of state and thermodynamics [7,8] which include the multi-cluster composition of matter [9,10,11,12,13,14,15,16,17,18,19,20,21]. Another aspect of the problem is the effects of light clusters in intermediate energy heavy ion collisions [22,23,24,25,26,27] which were extensively studied using various methods, see for example [28,29,30].…”