A Search for Pulsations in Late--Type Giants

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Session 22 -- Late-Type and Variable Stars
Oral presentation, Monday, 2:30-4:00, Dwinelle 145 Room

[22.02] A Search for Pulsations in Late--Type Giants

S. Horner (U. Chicago and HAO)

Observations of Arcturus ($\alpha$ Boo, K1III) have revealed oscillations with a period of 1.84 days and an amplitude of $160\ m\ s^{-1}$ that may be the result of solar--like p--mode oscillations (Smith, McMillan, and Merline 1987, Cochran, 1988, and Belmonte, Jones, Pall\'e, and Cort\'es 1990). I observed four stars, with a range of spectral types similar to that of Arcturus, for oscillations with periods on the order of 2 days. I observed $\alpha$ Ari, $\gamma$ Per, $\epsilon$ Tau, and $\alpha$ Aur (a close binary composed of two G giants) for 12 nights, observing each star $\sim5$ times per night, using the Kitt Peak National Observatory Coud\'e Feed telescope and Fiber Optic Echelle spectrograph to obtain high--resolution spectra. These stars have a range of spectral types from G0III to K2III. These stars were chosen because of their spectral similarity to Arcturus, their brightness, and their fundamental periods of $\sim 1$ day. By observing several giants with a range of effective temperature, we hope to gain some understanding of the stellar conditions required to support Arcturus--like pulsations.

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