The 1.7-day 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 on to the available photometric data suggests that the disk is well represented by a precessing steady-state configuration of accreting matter, essentially fills the critical Roche lobe of the collapsed companion, and is tilted out of the orbital plane by an angle which exceeds the complement of the orbital inclination.
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Gerend et al. (1976) studied this question.