Optical clues to the nature of Hercules X-1/HZ Herculis

The 1d/sub ./7 optical light curve of Her X-1/HZ Her varies in a highly systematic fashion over the 35 day X-ray on-off cycle. These variations can be reproduced in some detail by a relatively simple model based on a tilted, precessing accretion disk which serves three functions: a source of optical radiation, a shadowing body for X-ray emission, and an occulting body for the reemitted optical radiation from the heated face of HZ Her. A minimum variance relaxation of this model onto the available photometric data suggests that the disk is well represented by a precessing, steady-state configuration of accreting matter, that the disk essentially fills the critical Roche lobe of the collapsed companion, and that the disk is tilted out of the orbital plane by an angle which exceeds the complement of the orbital inclination. (AIP)