On the Line Profile Variations and Nonradial Pulsation Modes of ζ Tauri (HD 37202)

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Abstract
We present high signal-to-noise ratio spectra of the Hα, Hβ, and He I λλ4921,6678 spectral lines of the line profile variable and binary star ζ Tauri obtained between 1986 and 1988 using the University of Texas McDonald Observatory 2.1 m telescope. For intervals of sufficiently dense observation, we calculate power spectra for the time series defined at each point in the line profile in order to search for periodic variability. A single, prominent signal corresponding to a period of 0.777 ± 0.002 days dominates the power spectra over most of the profiles of each of the four lines. Based on the power distribution across the profile at this signal frequency, we argue that the only plausible explanation for these variations is photospheric nonradial pulsation (g-mode pulsations of degree l = -m = 2). We find no evidence for accompanying higher order NRP modes; however, the spectra do show weak, narrow, and nonperiodic features that cross the profiles on timescales similar to the NRP mode.