Period Changes in RV Tauri Stars: Observations and Simulations

Volume 21 number 2 (1992)

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John R. Percy

Erindale Campus, University of Toronto, Mississauga, Ontario, Canada L5L 1C6

Alexandra Csatary

Erindale Campus, University of Toronto, Mississauga, Ontario, Canada L5L 1C6

Ingrid Zorgdrager

Erindale Campus, University of Toronto, Mississauga, Ontario, Canada L5L 1C6

Abstract

We have determined the times and magnitudes of minimum brightness of two RV Tauri stars (SS Gem and V Vul) using data from the AAVSO and from the literature. We have used these to construct (O-C) diagrams. These are dominated by cyclic features with time scales ranging from several to several hundred pulsation periods. By constructing simulated (O-C) diagrams, we have shown that the observed (O-C) diagrams could be explained by the accumulation of random, cycle-to-cycle fluctuations in period, as in the case of most Mira stars.