HZ Her/Her X-1 binary system and the 35 day light curve
This video depicts an artist's impression of the HZ Her/Her X-1 binary system and shows how the 35 day X-ray light curve may arise.
The first sequence shows the tiny neutron star, surrounded by the accretion disk. The companion star, which is assumed to have filled its Roche lobe, transfers matter to the accretion disk as it orbits the neutron star.
As the animation proceeds a possible mechanism for generating the observed 35 day light curve is shown. The complex interplay between the precession of the accretion disk, wobbling of the outer regions of the disk, and eclipse by the companion star can give rise to the intricate 35 day variation in the X-ray emission.