Moving shadows on the dusty disks of young stars

Abstract

We investigate the formation of moving shadows on the circumbinary (CB) disk of young binary systems. Moving shadows can be created by a dusty disk wind of the secondary component. The densest parts of the dusty disk wind and the associated common envelope can be optically thick and may block the stellar radiation inside a certain solid angle, resulting in the appearance of a moving shadow zone. Its shape and size depends on the mass loss rate, the disk wind velocity, and optical properties of the dust. Our calculations show that the shadow zone is observable if the mass loss rate $\dot M_{\rm w}$ is greater than 10$^{-9} \,M_{\odot}$ per year. This shadow resembles a clock hand. If the orbit is an elliptical, the properties of this clock hand will change during the orbital motion of the secondary.