Relativistic equation of state of nuclear matter for supernova and neutron star

We study the evolution of a supernova core from the beginning of the gravitational collapse of a 15 M☉ star up to 1 s after core bounce. We present results of spherically symmetric simulations of core-collapse supernovae by solving general relativistic ν-radiation hydrodynamics in the implicit time differencing. We aim to explore the evolution of shock waves in the long term and investigate the formation of proto-neutron stars together with supernova neutrino signatures. These studies are done to examine the influence of the equation of state (EOS) on the postbounce evolution of shock waves in the late phase and the resulting thermal evolution of proto-neutron stars. We compare two sets of EOSs, namely, those by Lattimer and Swesty (LS-EOS) and by Shen et al. (SH-EOS). We found that, for both EOSs, the core does not explode and the shock wave stalls similarly in the first 100 ms after bounce. A revival of the shock wave does not occur even after a long period in either case. However, the recession of the shock wave appears different beyond 200 ms after bounce, having different thermal evolution of the central core. A more compact proto-neutron star is found for LS-EOS than SH-EOS with a difference in the central density by a factor of ~2 and a difference of ~10 MeV in the peak temperature. The resulting spectra of supernova neutrinos are different to an extent that may be detectable by terrestrial neutrino detectors.

https://iopscience.iop.org/article/10.1086/431788/pdf

Postbounce Evolution of Core-Collapse Supernovae: Long-Term Effects of the Equation of State

Hyperons and massive neutron stars: The role of hyperon potentials

Metamodeling for the nucleonic equation of state (EOS), inspired from a Taylor expansion around the saturation density of symmetric nuclear matter, is proposed and parameterized in terms of the empirical parameters. The present knowledge of nuclear empirical parameters is first reviewed in order to estimate their average values and associated uncertainties, and thus defining the parameter space of the metamodeling. They are divided into isoscalar and isovector types, and ordered according to their power in the density expansion. The goodness of the metamodeling is analyzed against the predictions of the original models. In addition, since no correlation among the empirical parameters is assumed a priori, all arbitrary density dependences can be explored, which might not be accessible in existing functionals. Spurious correlations due to the assumed functional form are also removed. This meta-EOS allows direct relations between the uncertainties on the empirical parameters and the density dependence of the nuclear equation of state and its derivatives, and the mapping between the two can be done with standard Bayesian techniques. A sensitivity analysis shows that the more influential empirical parameters are the isovector parameters ${L}_{\mathrm{sym}}$ and ${K}_{\mathrm{sym}}$, and that laboratory constraints at supersaturation densities are essential to reduce the present uncertainties. The present metamodeling for the EOS for nuclear matter is proposed for further applications in neutron stars and supernova matter.

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Equation of state for dense nucleonic matter from metamodeling. I. Foundational aspects

We study black hole formation and the neutrino signal from the gravitational collapse of a nonrotating massive star of 40 M☉. Adopting two different sets of realistic equations of state (EOSs) for dense matter, we perform numerical simulations of general relativistic ν-radiation hydrodynamics under spherical symmetry. We make comparisons of core bounce, shock propagation, evolution of nascent proto-neutron stars, and the resulting recollapse to a black hole to reveal the influence of EOSs. We also explore the influence of EOSs on neutrino emission during the evolution toward black hole formation. We find that the speed of contraction of the nascent proto-neutron star, whose mass increases quickly due to the intense accretion, is different depending on the EOS and that the resulting profiles of density and temperature differ significantly. The black hole formation occurs at 0.6-1.3 s after bounce, when the proto-neutron star exceeds its maximum mass, which is crucially determined by the EOS. We find that the average energies of neutrinos increase after bounce because of rapid temperature increase, but at different speeds depending on the EOS. The duration of neutrino emission up to black hole formation is found to be different according to different recollapse timing. These characteristics of neutrino signatures are distinguishable from those for ordinary proto-neutron stars in successful core-collapse supernovae. We discuss the idea that a future detection of neutrinos from a black hole-forming collapse will contribute to revealing the black hole formation and to constraining the EOS at high density and temperature.

https://iopscience.iop.org/article/10.1086/520876/pdf

H. Kuwabara

Papers

Relativistic mean-field theory with non-linear σ and ω terms for neutron stars and supernovae