• X-Ray Beaming and Mass Transfer in HZ Her

      Strittmatter, P. A.; Scott, J. S.; Whelan, J. A. J.; Wickramasinghe, D. T.; Univ Arizona, Steward Observ (Steward Observatory, The University of Arizona (Tucson, Arizona), 1973)
      The optical and X -ray properties of HZ Her are analyzed within the framework of a model in which the primary is illuminated by X -ray radiation from a degenerate secondary companion. System parameters are derived on the basis of a simplified model and yield a minimum distance to HZ Her of - 5 kpc. It is shown that the X -ray pulses and 35 day on -off characteristics as well as the shape and modulation of the optical light curve can be understood if (i) the primary is illuminated by X -ray emitted in a beam fixed in a rotating neutron star secondary undergoing forced precession and (ii) energy is supplied by mass transfer from primary to secondary resulting in the formation of a disc around the X -ray source which contributes significantly to the total light.