Evidence for Corotating Clouds in the Be Star ζ Tauri

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Abstract
We reexamine a time series of spectroscopic data of the Be star ζ Tauri obtained by Kaye & Gies. When the difference spectra are folded with the 0.777 day period, a distinctive pattern emerges. This pattern is not the standard "barber pole" diagram expected from nonradial pulsation but is instead a pattern of two sinusoidal variations of enhanced absorption having different amplitudes. We interpret these results as additional evidence for corotating clouds, recently suggested as an explanation of the variations observed in several other Be stars and as indirect evidence for the possible presence of magnetic fields.