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The 1972 Anomaly of XZ Cygni

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Marvin E. Baldwin

Andrews Air Force Base, Maryland

Abstract

XZ Cygni (193056) is an RR Lyrae type variable with a marked Blazko effect. It has created a great deal of interest among observers during the past several years because of its unusually large and progressive change of period. In less than seven years its period has decreased by 9.3 seconds and its cumulative deviation from the elements listed in the 1969 "General Catalogue of Variable Stars" now amounts to ten hours, only a little less than one full cycle (Fig.1). Based upon the visual maxima timings plotted in Figure 1 the current elements are determined to be" Max = 2440981.328 + 0.466471Ed. This represents an appreciable change of period from that reported earlier (Baldwin, in Mayall 1971).