Abstract
Abstract
Recent IXPE observations of Her X-1 reveal correlations between flux, polarization degree, and polarization angle with its 35 day superorbital cycle. These measurements have been interpreted as strong evidence that the 35 day period is driven by nearly free precession of the neutron star. We show that this interpretation carries far-reaching implications for the dynamics of the crustal superfluid. In particular, maintaining precession over the ∼50 yr observational baseline of Her X-1 would require that superfluid vortices remain unpinned for centuries and experience extremely weak mutual friction while traversing the heavy-ion lattice of the inner crust—conditions that challenge conventional wisdom and standard models of glitch dynamics.