# Cooling timescale for protoneutron stars and properties of nuclear matter: Effective mass and symmetry energy at high densities

## TL;DR

This study examines how the cooling timescale of protoneutron stars depends on the properties of dense nuclear matter, specifically effective mass and symmetry energy, using a systematic equation of state and neutrino diffusion modeling.

## Contribution

It introduces a new equation of state incorporating effective mass and symmetry energy at high densities, and analyzes their impact on protoneutron star cooling timescales.

## Key findings

- Larger effective masses lead to longer cooling timescales.
- Smaller symmetry energies at high densities also extend cooling durations.
- Results are consistent with previous models regarding effective mass and neutron star radius.

## Abstract

The cooling process of a protoneutron star is investigated with focus on its sensitivity to properties of hot and dense matter. An equation of state, which includes the nucleon effective mass and nuclear symmetry energy at twice the saturation density as control parameters, is constructed for systematic studies. The numerical code utilized in this study follows a quasi-static evolution of a protoneutron star solving the general-relativistic stellar structure with neutrino diffusion. The cooling timescale evaluated from the neutrino light curve is found to be longer for the models with larger effective masses and smaller symmetry energies at high densities. The present results are compared with those for other equations of state and it is found that they are consistent in terms of their dependences on the effective mass and neutron star radius.