EXOSAT and Einstein observations of the X-ray pulsar 4U 1145 619

Abstract

Results are presented of several Einstein and Exosat X-ray observations of 4U 1145 - 619, an X-ray pulsar orbiting the Be star HD 102567/Hen 715 with marked transient behavior. Pulse-timing analysis of data from imaging instruments on both missions was performed using a period-folding technique, which showed an interesting variation of the light curve shape. During observations at periastron, where the source was predictably brighter, a strong variability was observed on the time scale of several thousand seconds. The global X-ray picture presented can be interpreted in the context of an eccentric binary system with variable accretion, but especially the low-energy Exosat channel multiplier array pulsed light curve raises new questions on the detailed accretion geometry. 24 references.