Hard X-Ray Observations of Hercules X-1 by OSO-7

The UCSD X-ray telescope on the oSO-7 scanned the periodic variable X-ray source Her X-1 from 1972 May 30 to 1972 June 1. Analysis of the quick-look data in the 7-26 keV range shows low intensity at 12 2 hours UT, 1972 May 31, which is ezpected from the previously determined 1.7-day period. The source was observed in its high-intensity state 30 hours earlier than predicted from the Uhitru determination of the s5.7-day period and its phase. The spectrum over the 240 keV range in the high-intensity state can be fitted by 0.2S/E'. photons (cm2 5 kev) 1