GINGA observations of absorption dips in Hercules X-1

The absorption dips from the two years of Ginga observations of Hercules (Her) X-1 have been extracted and analysed. Both high-state and short-on dips were observed. The durations of the dips are measured and are not strongly correlated with orbital or 35-day phases. All dips show approximately the same absorbed flux but greatly differing amounts of unabsorbed flux. The dip column density shows evidence for dependence on orbital phase but not on 35-day phase. This is explained by an azimuthal dependence of the column density of the outer edge of the disc, which increases from a minimum near eclipse egress to a maximum near eclipse ingress. The behaviour of absorbed and unabsorbed spectral components during dips can be explained by an absorber passing in front of a source that has both point-like and extended components.