BeppoSAX spectroscopy of the Hercules X-1 short-on state

We present results of a 5.7 day duration BeppoSAX observation of the short- on state of Her X-l and a short observation during the decline of the prece ding main-on state. The 0.1-10 keV spectra can be fit with a power-law and blackbody model together with Fe emission features at 1.0 keV and 6.5 keV. During the later stages of the short-on state there are long intervals when the absorption is greater than or similar to 5 x 10(22) atom cm(-2). These intervals become longer and occur similar to 0.3 day earlier in each orbit al cycle as the short-on state progresses. During the intervals of high abs orption the 0.1 keV blackbody is still clearly detected. This may indicate the presence of separate scattered and absorbed spectral components, althou gh other explanations such as partial covering or a partially ionized absor ber cannot be excluded. During the rest of the short-on state the ratio of flux in the blackbody compared to the power-law is consistent with that in the main-on state. This supports the view that much of the 35 day modulatio n is caused by an energy independent process, such as electron scattering. The discovery of strong absorption late in the short-on state is consistent with the predictions of the warped disk model (Petterson 1977, see also Sc handl & Meyer 1994) where the end of the short-on state is caused by the ac cretion disk moving into the line of sight to the neutron star. The pulse p hase difference between the blackbody and the power-law maxima is 2.50 +/- 20 degrees in both observations (separated by 0.43 of a 35 day cycle). This constant phase difference is consistent with the blackbody originating at the inner edge of a precessing accretion disk.