Impact of the symmetry energy on the outer crust of nonaccreting neutron stars

The composition and equation of state of the outer crust of nonaccreting neutron stars is computed by using accurate nuclear mass tables. The main goal of the present study is to understand the impact of the symmetry energy on the structure of the outer crust. First, a simple toy model is developed to illustrate the competition between the electronic density and the symmetry energy, Then, realistic mass tables are used to show that models with a stiff symmetry energy-those that generate large neutron skins for heavy nuclei-predict a sequence of nuclei in the stellar environment that is more neutron rich than their softer counterparts. This result may be phrased in the form of a correlation: The larger the neutron skin of Pb-208, the more exotic the composition of the outer crust.