SPECTRAL SIGNATURES OF REPROCESSING ON THE COMPANION AND ACCRETION DISC OF HERCULES-X-1

We present optical spectrophotometric observations of the X-ray binary star Her X-l, The majority of line absorption and emission originates on or near the mass-losing primary with distributions over the inner face of the star, consistent with irradiation by X-rays from the envir ons of the compact companion, He II lambda 4686 Angstrom emission is d etected and found to be distributed closely about the neutron star and is a likely tracer of the accretion flow, Variations from orbit-to-or bit are a consequence of the 35-d quasi-periodicity that has been prev iously found over the entire observable spectrum, The mechanism provid ing the 35-d period is considered to be the precession of a tilted and twisted accretion disc about the neutron star, In order to determine the plausibility of the twisted-disc model we reconstruct the expected shadow of the disc across the heated inner face of the donor star, La rge-scale emission structure is reproduced, but the model fails to syn thesize finer observational details predicted by recent theoretical ca lculations.