Near-Infrared and TiO-band Photometry:

Rick Wasatonic and Guinan with M. Mirtorabi(Iran) are carrying out a pilot program of Wing near-IR, TiO-band, and V-band photometry of the RS Canum Venaticorum type, chromospherically active, G8 IV-III star $\vert lambda$ Andromedae. The primary aim is to investigate a possible relationship between variation of the $\sim 54$ day rotationally starspot modulated visual light curve and TiO absorption strength. The TiO ($\gamma$,0,0) absorption band strength at $\lambda =719$ nm is very sensitive to temperature for cool stars and manifests itself in cooler starspot regions (T$<=4000$ K). TiO photometry has an advantage over conventional photometry in that it provides unambiguous measures of the fractional cool starspot coverage. In addition, as the stars rotate, the variation in the TiO index yields information about the longitudinal distribution of the starspots. Importantly, combining the TiO photometry with the V-band and near-IR light curves allows the discrimination of white light faculae (= hot spot) and cool starspot contributions. Initial results of this study indicate that the observed V-band and near-IR continua light variations found for $\lambda$ And primarily arise from bright spot (plage) features rather than dark starspots as is usually assumed. This is in contrast to current theories that the visual light variation is solely due to dark spots. Models using both bright and dark spot features have been developed and are being used to fit the light and TiO-index curves. The models account for cool/hot spot characteristics such as projected filling factor and temperature. The long-term variation of the V-band observations and TiO index have been investigated to search for any activity cycles. The results of this study are published in the Astronomical Journal (2003) Vol. 125, 3265-3273.

Wing near-IR and TiO photometry of additional stars are being carried out by Wasatonic. These stars include the RS CVn variable stars $\kappa^{1}$ Ceti , IM Peg and continued observations of $\lambda$ And, the Mira variables: R Leo and Mira, and the pulsating red supergiants: Betelgeuse, $\alpha$ Her, TV Gem, and XX Per.