Skip to main content



Period Analysis of AAVSO Visual Observations of 55 Semiregular (SR/SRa/SRb) Variables


John R. Percy
Paul Jx Tan

Department of Astronomy and Astrophysics, University of Toronto. Toronto, ON M5S 3H4, Canada

Received April 26, 2012; revised June 21, 2012; accepted July 18, 2012


We have used AAVSO visual data, and Fourier analysis and self-correlation analysis, to study the periodicity of 55 semiregular (SR) variables—21 SRa and 34 SRb. According to the standard system of variable star classification, these are pulsating red giants, with visual amplitudes less than 2.5 magnitudes, which show noticeable periodicity (SRa) or less-obvious periodicity (SRb). We find that their behavior ranges from highly periodic to irregular; some are not significantly variable. We have used a simple index, based on self-correlation analysis, to show that, on average, the SRa variables have a larger component of periodicity than the SRb variables, as expected. The distributions of this index for the two groups, however, overlap considerably. Of our 55 stars, 11 definitely or possibly show two radial periods, and at least 16 definitely or possibly show a long secondary period. We also analyzed three non-SR stars: T Cet is a double-mode SRc star; T Cen is an RVa star which should be reclassified as RVb; V930 Cyg is an irregular (Lb) star with a strong 250-day period.

link to article on ADS

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484