AAVSO: American Association of Variable Star Observers

An Update on the Periods and Period Changes of the Blazhko RR Lyrae Star XZ Cygni

Volume 49 number 1 (2021)

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Dylan Kaneshiro
‘Iolani School, 563 Kamoku Street, Honolulu, HI 96826; dtk2101@iolani.org
Horace A. Smith
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824; smithhh@msu.edu
Gerard Samolyk
P. O. Box 20677, Greenfield, WI 53220; gsamolyk@wi.rr.com

Abstract

XZ Cygni is an RR Lyrae variable that underwent relatively large changes in its primary and Blazhko periods during the 20th century. Here we use AAVSO photometry obtained between 2001 and 2019 to extend previous studies of this star. Whereas XZ Cygni’s fundamental mode and Blazhko periods changed dramatically between 1965 and 1979, those periods have been more stable since the 1980s, although the fundamental period has not been entirely constant. We compare the period change behavior of XZ Cygni with theoretical predictions of period change.