Active asteroid belt causes the UXOR phenomenon in RZ Piscium

Abstract

We report the discovery of mid-infrared excess emission in the young object RZ Psc. The excess constitutes ~8% of its L_bol and is well fit by a single 500 K blackbody, implying a dust-free region within ~0.7 AU for optically thick dust. The object displays dust obscuration events (UXOR behaviour) on a time scale that suggests dusty material on orbits of ~0.5 AU. We also report a 12.4-year cyclical photometric variability that can be interpreted as caused by perturbations in the dust distribution. The system is characterized by a high inclination, marginal extinction (during bright photometric states), a single temperature for the warm dust, and an age estimate that puts the star beyond the formation stage. We propose that the dust occultation events present a dynamical view of an active asteroid belt whose collisional products sporadically obscure the central star.