Color Indices of T Tauri Stars in Variable Circumstellar Extinction Models

Variable circumstellar extinction models as applied to T Tauri stars are considered. In contrast to hotter UX Ori stars, for which simplified eclipse models are applicable, the star is deemed a point source of light, while the circumstellar dust clouds obscuring the star are assumed to be homogeneous. In the case considered here, both these simplifications may not work. Hot accretion spots are formed through accretion on T Tauri stars, while the dust structures obscuring the star from the observer can be inhomogeneous within the stellar disk. The families of color–magnitude diagrams have been computed by taking into account these two factors. It is shown that in such models the color tracks on the diagrams can differ greatly in shape from those computed in eclipse models for hot UX Ori stars. The results obtained may be applicable to AA Tau stars demonstrating eclipses by the inner circumstellar disk regions.