Further Ariel V observations of Hercules X-1

Abstract
Detailed spectra obtained with the Ariel V satellite for the turn-on and off of Hercules X-1 from the extended low are presented. We find that the obscuring region assumed responsible for the 35-day cycle lies well within any accretion disc surrounding the neutron star. This conflicts with some previous models of the system. A light curve of part of the secondary on-state is also presented and a new value of the pulse period derived.