Studies of RV Tauri and SRD Variables

Volume 43 number 2 (2015)

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John R. Percy

Department of Astronomy and Astrophysics and Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada; john.percy@utoronto.ca

Abstract

AAVSO visual and Johnson V observations of 42 RV Tauri and 30 yellow semiregular (SRD) variables have been time-series analyzed with the AAVSO vstar package. The DCDFT routine was used to determine periods and mean amplitudes, and the WWZ (wavelet) routine was used to study changes in the amplitudes of these stars. For almost half of the stars, improved periods and/or classifications were obtained. For others, existing classifications and periods were confirmed or supported. As was previously found for a subset of RV and SRD stars, the pulsation amplitudes vary by factors of up to 10, on median time scales of about 22 pulsation periods for the RV stars, and about 25 pulsation periods for the SRD stars; these two values are not significantly different. This behavior is consistent with that of pulsating red giants and supergiants. The cause of the pulsation amplitude variations remains unknown.