Nuclear physics inputs for modeling crustal properties of proto-neutron stars

Hoa Dinh Thi (Rice University, USA)

Proto-neutron stars are born hot, with temperatures exceeding few 10^10 K. In these conditions, the crust of the proto-neutron star is expected to be made of a Coulomb liquid and composed of an ensemble of different nuclear species. In this work, we performed a study of the beta-equilibrated proto-neutron-star crust in the liquid phase in a one-component approximation and a self-consistent multi-component approach. In the one-component calculation, we showed that including the translational free energy can significantly reduce the optimal number of nucleons in the clusters and lead to an early dissolution of clusters, thus highlighting the importance of its inclusion when modelling the finite-temperature (proto-)neutron star inner crust. To take into account the whole nuclear distribution, we developed a self-consistent multi-component approach. We found that the abundance of light nuclei becomes important, and eventually dominates the whole distribution, at higher density and temperature in the crust. This reflects in the calculation of the impurity parameter, which, in turn, may have a potential impact on neutron-star cooling. To quantify the possible contribution of particularly hydrogen and helium isotopes in crustal impurity, we employed different versions of the relativistic mean-field approach where in-medium binding energy shifts were included. Our results suggest that the impurity factor associated with these clusters is very small and can be neglected in transport calculations, even if some model dependence is observed.