Extreme-Ultraviolet Explorer observations of Hercules X-1 at the end of the short high state

Observations of Hercules X-1 by the Extreme-Ultraviolet Explorer at the end of the X-ray short high state are reported here. Her X-1 is found to exhib it a strong orbital modulation of the EUV flux, with a large dip superposed on a broad peak around orbital phase 0.5 when the neutron star is closest the observer. Alternate mechanisms for producing the observed EUV light cur ve are modeled. We conclude that (1) the X-ray-heated surface of the compan ion is too cool to produce enough emission, (2) the accretion disk can prod uce enough emission but does not explain the orbital modulation, and (3) th e ref-lection of X-rays off the companion can produce the shape and intensi ty of the observed light curve. The only viable cause for the large dip at orbital phase 0.5 is shadowing of the companion by the accretion disk.