A Search for Pulsations in Late-Type Giants

Details A Search for Pulsations in Late-Type Giants A Search for Pulsations in Late-Type Giants

Jan 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........29h&link_type=abstract

PhD Dissertation, Chicago Univ. Chicago, IL United States

Physics

2

Giant Stars, Late Stars, Unsteady Flow, Doppler Effect, Phase Shift, Emission Spectra, Stellar Oscillations, Stellar Physics, Binary Stars, Time Series Analysis, Luminaires, Echelle Gratings, Spectrographs, Molecular Absorption, Iodine, Resolution Cell, Telescopes, Astronomical Observatories

Scientific paper

I discuss the techniques used to measure Doppler shifts to high precision using echelle spectrographs in order to detect oscillations on stars other than the Sun. I compare the use of hollow-cathode lamps to molecular iodine absorption cells as wavelength references. To develop and demonstrate these techniques, I observed four late-type giant stars using the Kitt Peak National Observatory Coude Feed Telescope and Fiber Optic Echelle Spectrograph. I chose these stars - which range in spectral types from G8III to K2III - because of their spectral similarity to Arcturus (Alpha Boo, K1III) for which earlier observations revealed oscillations with a period of 1.84 days and an amplitude of 160 meters per second. I observed Alpha Air, Gamma Per, Epsilon Tau, and Alpha Aur (a close binary composed of two G giants) for 12 nights, observing each star approximately 5 times per night in order to detect oscillations with periods on the order of 2 days. No oscillations were detected on any of the four stars observed in this campaign. The upper limits of the oscillation amplitudes at periods comparable to those seen on Arcturus fall well below those observed for Arcturus. Continued observations of Arcturus are required to determine whether the observed period and amplitude are stable, or if the structure of Arcturus is different from the late-type giants observed in this campaign.

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