  We present a broad-band X-ray timing study of the variations in pulse
behavior with superorbital cycle in the low-mass X-ray binary Her X-1. This
source shows a 35-day superorbital modulation in X-ray flux that is likely
caused by occultation by a warped, precessing accretion disk. Our data set
consists of four joint XMM-Newton and NuSTAR observations of Her X-1 which
sample a complete superorbital cycle. We focus our analysis on the first and
fourth observations, which occur during the bright "main-on" phase, because
these observations have strongly detected pulsations. We added an archival
XMM-Newton observation during the "short-on" phase of the superorbital cycle
since our observations at that phase are lower in signal to noise. We find that
the energy-resolved pulse profiles show the same shape at similar superorbital
phases and the profiles are consistent with expectations from a precessing
disk. We demonstrate that a simple precessing accretion disk model is
sufficient to reproduce the observed pulse profiles. The results of this model
suggest that the similarities in the observed pulse profiles are due to
reprocessing by a precessing disk that has returned to its original precession
phase. We determine that the broad-band spectrum is well fit by an absorbed
power law with a soft blackbody component, and show that the spectral continuum
also exhibits dependence on the superorbital cycle. We also present a brief
analysis of the energy resolved light curves of a pre-eclipse dip, which shows
soft X-ray absorption and hard X-ray variability during the dip.
