Heavy Nuclei as Thermal Insulation for Proto-Neutron Stars

TL;DR

This paper investigates how heavy nuclei in proto-neutron stars influence neutrino emission and cooling, highlighting the role of nuclear equation of state parameters in thermal insulation effects.

Contribution

It demonstrates that heavy nuclei act as thermal insulators affecting neutrino signals, with the impact depending on the nuclear equation of state at different densities.

Findings

Neutrino luminosity and mean energy are higher with softer EOS.

Cooling time scale is longer for softer EOS.

Heavy nuclei significantly influence neutrino interactions near the PNS surface.

Abstract

A proto-neutron star (PNS) is a newly formed compact object in a core collapse supernova. In this Letter, the neutrino emission from the cooling process of a PNS is investigated using two types of nuclear equation of state (EOS). It is found that the neutrino signal is mainly determined by the high-density EOS. The neutrino luminosity and mean energy are higher and the cooling time scale is longer for the softer EOS. Meanwhile, the neutrino mean energy and the cooling time scale are also affected by the low-density EOS because of the difference in the population of heavy nuclei. Heavy nuclei have a large scattering cross section with neutrinos owing to the coherent effects and act as thermal insulation near the surface of a PNS. The neutrino mean energy is higher and the cooling time scale is longer for an EOS with a large symmetry energy at low densities, namely a small density derivative coefficient of the symmetry energy, $L$.