On the Nature of the Rapid Color Changes of the UX Ori Star RY Lupi at Deep Minima

We propose an explanation for the rapid color changes on the color–magnitude diagrams observed by Gahm et al. in the T Tauri star RY Lup during its deep minima. Our calculations have shown that the hot accretion spot on the stellar surface in combination with the inhomogeneous structure of the gas–dust clouds obscuring the star can be responsible for these changes. The observed rate of of the color changes allows one to estimate the velocity of the screen across the stellar disk ≈100 km s ^-1 . This velocity is close to the typical gas velocities near T Tauri stars.