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H.A. Smith, A. LaCluyze, E.-M. Gill, A. Hedden, K. Kinemuchi, A.M. Rosas, B.J. Pritzl, B. Sharpee, K. Robinson (Mich. State), M. Baldwin, G. Samolyk (AAVSO)
The RR Lyrae star XZ Cygni has long been known to exhibit a secondary Blazhko period. In the 1970s the length of this Blazhko period increased from 57.3 days to about 58.3 days, coincident with a decrease in the period of XZ Cygni's fundamental pulsation mode. We have carried the story of XZ Cygni up to the year 2000, analyzing CCD and visual photometry to determine the recent behavior of both its primary pulsation period and its secondary Blazhko period. The observed changes in the length of the Blazhko period for XZ Cygni constrain theoretical explanations of the Blazhko Effect, particularly those which require that the Blazhko period and the rotation period of the star be equal.
This work has been supported in part by the National Science Foundation.