Analysis of AAVSO Visual Measurements of T Tauri Variable Stars

Volume 35 number 1 (2007)

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John R. Percy

Rohan Palaniappan

Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON,

Abstract

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-mainsequence 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 selfcorrelation 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.