RXTEObservations of Hercules X‐1 during the 1998 July Short High State

We present RXTE monitoring of the eclipsing X-ray binary Hercules X-1conducted over the short-high state of July 1998. This was one of the lastmajor short-high states before the source entered an anomalous low-state ofactivity. A comparison with previous epochs finds no evidence for specialbehavior during these observations. We determine orbital and pulsar spinperiods to facilitate measurements period derivatives during the subsequentanomalous low state and during the next epoch of high-state activity.Spectrally, the decay of the short-high state and concurrent pre-eclipse dipsare consistent with obscuration of a central X-ray source by a cloud ofnon-uniform column density. The standard model of a warped accretion disk offinite vertical scale height fits the characteristics of this absorber well.Pre-eclipse dips have durations a factor of a few longer than thecharacteristic durations of dips during main-high states. Pulse profilestructure increases in complexity towards the tail of the short-high statesuggesting changes in accretion curtain geometry.Comment: 19 pages, 10 figures. ApJ, in pres