1999A&A...350L...5P

Result. of a 1999 July 8-10 BeppoSAX observation during an anomalous low-state of HerX-1 are presented. The standard on-state power-law and blackbody continuum model is excluded at high confidence unless partial covering is included. This gives a power-law photon index of 0.63±0.02 and implies that 0.28±0.03 of the flux undergoes additional absorption of (27±7)x10²²atom/cm². 11% of the observed 0.1-10keV flux is from the 0.068±0.015keV blackbody. 1.237747(2)s pulses with a semi-amplitude of 2.1±0.8% are detected at >99.5% confidence and confirmed by RXTE measurements. This implies that Her X-1 underwent substantial spin-down close to the start of the anomalous low-state. The spectral and temporal changes are similar to those recently reported from 4U 1626-67. These may result from a strongly warped disk that produces a spin-down torque. The X-ray source is then mostly viewed through the inner regions of the accretion disk. A similar mechanism could be responsible for the Her X-1 anomalous low-states. Shadowing by such an unusually warped disk could produce observable effects in the optical and UV emission from the companion star.