Multiwavelength studies of hercules X-1 during short high and anomalous low states: On-again, off-again

We present results from multiwavelength observations of the Hercules X-1 sy stem during a short high state (SHS) and during an anomalous low state (ALS ). The magnitude of deviation from spin-up appears to be positively correla ted with duration of the ALS. Such a correlation is consistent with an inte rpretation of the ALS in terms of a change in mass accretion rate that caus es the disk to tilt and twist beyond the normal deviations that cause the 3 5 day cycle. A larger deviation from the average (M)over dot results in a s tronger disruption of the disk and causes the disk to take longer to settle back to its "normal" 35 day behavior. Our model-which includes X-ray heati ng of the disk and companion star, shadowing of the X-ray flux by the disk, and a contribution to the continuum emission from the accretion stream or hot spot-can consistently explain the observed changes in X-ray, ultraviole t (UV), and optical continuum light curves for both the SHS and ALS. The Hu bble Space Telescope (HST) and Space Telescope Imaging Spectrograph (STIS) observations presented here are the first UV observations of sufficient spe ctral and temporal resolution to construct Doppler tomograms of the line em ission. Doppler tomograms of the UV emission lines during SHS and ALS show the majority of the emission coming from the surface of the companion star rather than from the accretion disk. Tomograms made after separating the N V emission lines into broad and narrow components suggests that while the n arrow component is associated with emission from the companion star, the br oad component may be associated with emission from a distorted disk. The Do ppler maps also show that heating over the inner face of HZ Her is not unif orm and imply partial eclipse of the UV line emission by an accretion strea m and/or hot spot.