RXTE/PCA observations of Hercules X-1: New features of the orbital and 35-day folded light curves.

Hercules X-1 is a well-known and much studied X-ray binary. It is a 1.7 day eclipsing system and has a 35-day cycle consisting of consecutive high, low, short-high and low states. The cause of the cycle is understood to be changing obscuration of the line-of-sight to the neutron star by a warped accretion disk, which precesses with a 35 day period. All of the X-ray observations of Hercules X-1 taken with the Proportional Counter Array (PCA) instrument of the Rossi X-ray Timing Explorer (RXTE) satellite are analyzed. 35-day phase is determined using a study of RXTE All Sky Monitor data and verified with the PCA data. New orbital and 35-day folded light curves are presented. Absorption dips are identified and studied as a function of orbital and 35-day phase. The extensive RXTE/PCA data give a considerably better and different picture of the dip phenomena than previously possible. [ABSTRACT FROM AUTHOR]