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Analysis of AAVSO Visual Measurements of T Tauri Variable Stars

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John R. Percy
Rohan Palaniappan

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

Presented at the 95th Spring Meeting of the AAVSO, May 6, 2006; received August 31, 2006, revised December 1, 2006, accepted December 1, 2006

T Tauri stars are stars in the final stages of birth, in which accretion from a circumstellar disc of gas and dust is still taking place. By some definitions, T Tauri stars include only GKM types; in this paper, we include higher-mass pre- main-sequence variables as well. AAVSO observers have made tens of thousands of visual measurements of T Tauri stars, but most of the measurements were never validated because their scientific value was not clear. We have used Fourier and self-correlation techniques to analyze AAVSO visual measurements of eleven T Tauri stars, namely AB Aur, RW Aur, SV Cep, R CrA, S CrA, RY Lup, R Mon, UX Tau, BP Tau, DL Tau, and WW Vul. We have compared the results to those obtained from long-term CCD measurements of the same stars. Using our methods of analysis, it is possible to detect periods, even if the amplitude is only a few hundredths of a magnitude, or to set upper limits, as small as 0.01 magnitude, on any periodic component to the variability. For each star, periodic or not, we have determined the variability "profile"--the relation between time scale and amount of variability. We conclude that the AAVSO visual measurements of T Tauri stars have definite scientific value. It would therefore be desirable to validate the visual measurements of other T Tauri stars.

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