Inhomogeneous dust eclipses in young stars. The case of CQ Tauri

Abstract

We find that dust clouds which eclipse young stars obscure the stellar disc inhomogeneously. In the particular case of CQ Tau, we find isolated optically thick structures with sizes $\lesssim0.6R_*$ and derive the typical $A_{V}$ gradient in the plane of the sky, finding it as high as a few magnitudes per stellar radius. The large extinction gradients and complex structure of the obscuring clouds lead not only to a noticeable Rossiter--McLaughlin effect, but also to complex and variable shaping of stellar absorption lines.