Analysis of AAVSO Visual Observations of Small-Amplitude Red Variables: An Autocorrelation Approach (Abstract)

Volume 20 number 2 (1991)

John R. Percy

University of Toronto, Erindale College, Department of Astronomy, Missisauga, Ontario, Canada

Li V. Sen

University of Toronto, Erindale College, Department of Astronomy, Missisauga, Ontario, Canada

Abstract

(Abstract only) Small-amplitude red variables are M giants pulsating with periods of 20 to 200 days, and amplitudes of up to a magnitude or more. Over the years, AAVSO observers have made thousands of visual estimates of dozens of these stars, and AAVSO photoelectric observers are now monitoring about 50 of them. We have developed a simple autocorrelation method of analysis, and have applied it successfully to AAVSO visual observations of RZ Ari, W Boo, FS Com, W Cyg, U Del, EU Del, and rho Per. The method has several advantages over traditional Fourier methods; it is particularly useful for stars which are not strictly periodic, or which vary on two or more significantly different time scales. IT is able to accommodate data with large seasonal gaps and with large observational scatter, as long as the data are reasonably dense in time.