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The 218 day period of the peculiar late B-type star HD 101584

Eric J. Bakker·Henny J. G. L. M. Lamers·L. B. F. M. Waters·Christoffel Waelkens
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Abstract

We have searched for periodicity in the photometric and spectroscopic variations of the enigmatic star HD 101584 and found a long-term variability on a typical time scale of 1700 days (4.7 years) and a highly significant 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). The Doppler velocities of the high-excitation photospheric absorption lines (HeI and CII) seem to be variable with the photometric period. Our data favor the 218 day period for the Doppler velocities with a small probability that the true period is 436 days. We argue that HD 101584 is a close (highly) eccentric 218 day binary system with a low-mass unseen secondary. The photometric and Doppler variations are attributed to changes in the velocity law and mass-loss rate of the stellar wind which lead to asymmetric line profiles and a phase dependent Balmer discontinuity. Binary interaction is responsible for the changes in velocity law and mass-loss rate leading to the observed phenomena.

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Eric J. Bakker, Henny J. G. L. M. Lamers, L. B. F. M. Waters, Christoffel Waelkens. 1995-11-10. The 218 day period of the peculiar late B-type star HD 101584. https://arxiv.org/abs/astro-ph/9511043

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