Rossi X-Ray Timing Explorer All-Sky Monitor observations of the 35 day cycle of Hercules X-1

Her X-l has been monitored nearly continuously in soft X-rays (2-12 keV) si nce 1996 February by the Ah-Sky Monitor on board the Rossi X-Ray Timing Exp lorer. We present an analysis of these observations, which include 23 conti guous 35 day cycles. We present the best-yet average 35 day cycle light cur ve for Her X-l. Thirty-five day light-curve features such as eclipses and a bsorption dips, and the alternating occurrence of the main high and short h igh states, are well measured. The occurrence of X-ray eclipse during the l ow state is confirmed, as is the presence of main high states that "turn-on " sharply at orbital phases 0.23 and 0.68. The main high state covers 35 da y phases 0-0.31, and the short high state covers phases 0.57-0.79, with pha se 0 defined by main high state turn-on. We find extended ingresses and egr esses for the short high slate. Marching preeclipse absorption dips progres sively become shallower during the main high state. The marching preeclipse dip period is best determined from reanalysis of archival data as 1.651 +/ - 0.002 days if the dip marching can be extrapolated from the main high sta te into he short high state or 1.646 +/- 0.003 using dips within single mai n high states alone.