  We present a broad-band X-ray study of the effect of superorbital periods on
X-ray spectra and pulse profiles in the neutron star X-ray binaries LMC X-4 and
SMC X-1. These two sources display periodic or quasi-periodic variations in
luminosity on the order of tens of days which are known to be superorbital, and
are attributed to warped, precessing accretion disks. Using joint NuSTAR and
XMM-Newton observations that span a complete superorbital cycle, we examine the
broad-band spectra of these sources and find the shape to be well described by
an absorbed power law with a soft blackbody component. Changes in spectral
shape and pulse profile shape are periodic with superorbital period, as
expected from a precessing disk. We perform X-ray tomography using the changes
in pulse profiles to model the geometry and kinematics of the inner accretion
disk. Our simple beam and inner disk geometric model indicates that the long
term changes in soft pulse shape and phase are consistent with reprocessed
emission from a precessing inner disk.
