Clumpy Accretion As a Possible Cause of Prolonged Eclipses in UX Ori Stars

We propose a model of deep and prolonged eclipses in young UX Ori stars. Some of these events last for decades and existing models cannot explain them. We show that such eclipses can be caused by the infall of gas and dust clumps from the remnants of the protostellar cloud onto the protoplanetary disk. The perturbation in the disk caused by the infall of a clump leads to a burst of accretional stellar activity and, as a consequence, to a strengthening of the disk wind. If the circumstellar disk is tilted at a small angle to the line of sight, then the dust raised by the wind from the disk surface can cause a dramatic decrease in the stellar brightness that can last for decades.