We report on a pre-eclipse dip of the X-ray binary Her X-1 observed by the Rossi X-ray Timing Explorer (RXTE) in July 1996. We present the evolution of the spectral parameters in the 3-18 keV range with a temporal resolution of 16 s and show that the varying flux of the spectrum can be interpreted solely by a time varying column density. We also find that the lightcurve is characterized by symmetric substructures with recurrence time of a few minutes that can be successfully modeled by Gaussian profiles.
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