THE 218 DAY PERIOD OF THE PECULIAR LATE B-TYPE STAR HD-101584

We have searched for periodicity in the photometric and spectroscopic variations of the enigmatic star HD 101584 and found a long-term varia bility on a typical time scale of 1700 days (4.7 years) and a highly s ignificant period of 218 +/- 0.7 day. This period is most prominently present in the photometric indices which are a measure for the Balmer jump (Geneva d and Stromgren c(1)(0)). The Doppler velocities of the h igh-excitation photospheric absorption lines (HeI and CII) seem to be variable with the photometric period. Our data favor the 218 day perio d for the Doppler velocities with a small probability that the true pe riod is 436 days. We argue that HD 101584 is a close (highly) eccentri c 218 day binary system with a low-mass unseen secondary. The photomet ric and Doppler variations are attributed to changes in the velocity l aw and mass-loss rate of the stellar wind which lead to asymmetric lin e profiles and a phase dependent Balmer discontinuity. Binary interact ion is responsible for the changes in velocity law and mass-loss rate leading to the observed phenomena.