Periodicity Analysis of the Semiregular Variable Star EV Aquarii

Volume 39 number 2 (2011)

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Emil Terziev

Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada; address correspondence to john.percy@utoronto.ca

John R. Percy

Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada; address correspondence to john.percy@utoronto.ca

Arne A. Henden

AAVSO, 49 Bay State Road, Cambridge, MA 02138; arne@aavso.org

Abstract

EV Aquarii is a variable star which was formerly misclassified as a cataclysmic variable, but photometric observations and colour indices have since indicated that it is most likely a semiregular M giant. The authors of this paper have used self-correlation analysis and Fourier analysis to determine the variability profile of the star. Data from the AAVSO International Database, the All-Sky Automated Survey, The Amateur Sky Survey, and co-author Arne Henden were used. The period of variation has been found to be 123.6 days ± 2.1 days. The amplitude of this variation is not constant; it changes with time between approximately 0.4 and 1.0 magnitude. There were no indications of a longer secondary period, though there has been observed an instance of a transient period of variation on a shorter timescale of about 40 days. There was no evidence found of periodic variation of the color differences.