AAS 202nd Meeting, May 2003
Session 28 Young Stars and Star Formation
Poster, Tuesday, May 27, 2003, 10:00am-6:30pm, West Exhbit Hall

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[28.02] TiO and VRI Photometry of the T Tauri Star V410 Tauri: A Proxy for the One Million Year Old Embryonic Sun

M.V. Lesniak, E.F. Guinan, L.E. DeWarf, G.P. McCook (Villanova University)

V410 Tauri is a weak emission-line T Tauri (WTT) star that has been extensively studied over nearly all wavelengths. This star has very large (nearly) periodic light variations (\DeltaV \approx 0.4 mag) and with a period of P ~ 1.87 days. Modeling of the light curves and Doppler imaging techniques indicate the light variations primarily arise from the rotational modulation by large dark starspot regions, distributed unevenly over its surface. Bright (warm) regions also appear to be present. The rapid rotation of the star (P = 1.87d; v sin i = 70 km/s), coupled with its expected deep convective zone (~K4 V-IV spectral type), insure a vigorous magnetic dynamo that results in the observed large starspot coverage and related strong coronal X-ray and chromospheric emissions.

We present new TiO narrow, and VRI wide-band, photometry of V410 Tau, carried out with the recently refurbished photoelectric photometer attached to the 0.8 m Four College APT, located in southern Arizona. A TiO-index is formed from the photometry. This TiO-index, when calibrated with Wing standard stars, yields a measure of the strength of the TiO absorption band at 719 nm relative to a continuum region at 754 nm. TiO absorption is very sensitive to Teff for cool stars and is also present in cooler sunspot and starspot regions. TiO photometry, coupled with VRI photometry, is used to determine the properties of the surface features on V410 Tau. TiO photometry provides unambiguous measures of the fractional cool starspot coverage. Importantly, combining the TiO with the VRI photometry allows the discrimination of white-light faculae (= hot spots) and cool (TiO absorption) starspots. During 2003, there is a good correlation between the light variations and TiO-index in the sense that the TiO absorption is strongest when the star is faintest.

The results of this program will be discussed along with earlier VRI photometry of V410 Tau obtained with the same telescope during 1993-1995. Discussions of previous work and more refined deteminations of age and mass of V410 Tau also will be presented. This research is supported by NSF/RUI Grant AST-00 71260.

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