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The Application of Visual Observations to the Study of a Small-Amplitude Variable Star: Rho Cassiopeiae

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John R. Percy

Virginia A Fabro

Erindale College and

Department of Astronomy, University of Toronto, Toronto, Ontario, Canada M5S 1A1

Abstract

We have used AAVSO and BAA visual observations to study the variability of the extremely luminous yellow supergiant Rho Cassiopeiae. We first compared 30-day means of the AAVSO and BAA visual observations with each other and with photoelectric photometry, in order to identify any systematic errors. We then investigated the periodicity of the star by applying Fast Fourier Transform and autocorrelation methods to the visual means. There is a characteristic time scale of 275 to 400 days, which is consistent with the pulsational time scale for such a star, but the variability is far from regular. The star bears some resemblance to the R CrB stars (with which it is sometimes classified). Our results indicate that, in some cases, moderately small-amplitude variables can be studied visually, as long as the observations are made carefully, consistently, and sufficiently frequently.