Binary modulation and transient periodic variations in X-ray emissionfrom the AM HER binary H 0139-68.

The authors present the results of a detailed timing analysis of the soft X-ray data on the AM Her type binary H0139-68, obtained with HEAO-1 and Einstein satellites. It is demonstrated that the X-ray flux from H0139-68 is modulated at the 113.6363 min orbital period of its optical counterpart. The imaging proportional counter (IPC) data obtained with the Einstein satellite show a high and low state in the X-ray source, consistent with the binary modulation seen in the HEAO-1 data. Transient X-ray pulsations with a period of ≡275 s are observed in the IPC data during the high state. It is shown that the present optical and X-ray data rule out the presence of an accretion disc in the binary system.