Triaxial nuclear models and the outer crust of nonaccreting cold neutron stars

Abstract

The properties and composition of the outer crust of nonaccreting cold neutron stars are studied by applying the model of Baym, Pethick, and Sutherland (BPS) and taking into account for the first time triaxial deformations of nuclei. Two theoretical nuclear models, Hartree-Fock plus pairing in the BCS approximation (HF-BCS) with Skyrme SLy6 parametrization and Hartree-Fock-Bogolyubov (HFB) with Gogny D1S force, are used to calculate the nuclear masses. The two theoretical calculations are compared; points of comparison of the two calculations include their neutron drip lines, binding energies, magic neutron numbers, and the sequence of nuclei in the outer crust of nonaccreting cold neutron stars, with special emphasis on the effect of triaxial deformations. The BPS model is extended by higher-order corrections for the atomic binding, screening, exchange, and zero-point energies. The influence of the higher-order corrections on the sequence of the outer crust is investigated.