From neutron skins and neutron matter to the neutron star crust

Abstract

We present the first Bayesian inference of neutron star crust properties to incorporate neutron skin data, including the recent PREX measurement of the neutron skin of $^{208}$Pb, combined with recent chiral effective field theory predictions of pure neutron matter with statistical errors. Using a compressible liquid drop model with an extended Skyrme energy-density functional, we obtain the most stringent constraints to date on the transition pressure $P_{\rm cc}=0.33^{+0.07}_{-0.07}$ MeV fm$^{-3}$ and chemical potential $\mu_{\rm cc}=12.6^{+1.8}_{-1.9}$ MeV (which control the mass, moment of inertia and thickness of a neutron star crust), the proton fractions that bracket the pasta phases $y_{\rm p}=0.115^{+0.016}_{-0.017}$ and $y_{\rm cc}=0.041^{+0.007}_{-0.006}$, as well as the relative mass and moment of inertia $\Delta M_{\rm p} / \Delta M_{\rm c}\approx \Delta I_{\rm p} / \Delta I_{\rm c} = 0.54^{+0.05}_{-0.09}$ and thickness $\Delta R_{\rm p} / \Delta R_{\rm c}=0.129^{+0.019}_{-0.030}$ of the layers of non-spherical nuclei (nuclear pasta) in the crust.