From neutron skins and neutron matter to the neutron star crust
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 $μ_{\rm cc}=12.6^{+1.8}_{-1.9}$ 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 $ΔM_{\rm p} / ΔM_{\rm c}\approx ΔI_{\rm p} / ΔI_{\rm c} = 0.54^{+0.05}_{-0.09}$ and thickness $ΔR_{\rm p} / ΔR_{\rm c}=0.129^{+0.019}_{-0.030}$ of the layers of non-spherical nuclei (nuclear pasta) in the crust.