Period Changes in the Long Period Variable TY Cas

Volume 31 number 1 (2003)

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Martha L. Hazen

Harvard

Janet A. Mattei

AAVSO,

Abstract

mid-2002 in the long period, Mira-type variable star TY Cassiopeiae by combining 275 photographic magnitudes and useful upper limits of brightness from the Harvard College Observatory plate collection with more than 1750 visual, photovisual, and CCD(V) magnitude measurements and upper limits from the AAVSO International Database. The star is shown to have a period decrease from 645 to 550 days during the early years of the 1900s, then the period steadily increased to 645 days until the 1980s, and then it stabilized. These changes are qualitatively similar to the predictions of helium-shell flash models of Wood and Zarro (1981). Thus, TY Cas may be an excellent candidate for a star undergoing a helium-shell flash. Link to ADS abstract, article and citation information