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.
The star RZ Psc is one of the most enigmatic members of the UX Ori star family. It shows all properties that are typical for these stars (the light variability, high linear polarization in deep minima, the blueing effect) except for one: it lacks any signatures of youth. With the lithium line 6708 Å as a rough estimate for the stellar age, we show that the "lithium" age of RZ Psc lies between the age of stars in the Pleiades (∼70 Myr) and the Orion (∼10 Myr) clusters. We also roughly estimated the age of RZ Psc based on the proper motion of the star using the Tycho-2 catalog. We found that the star has escaped from its assumed birthplace near to the Galactic plane about 30−40 Myr ago. We conclude that RZ Psc is a post-UXOr star, and its sporadic eclipses are caused by material from the debris disk.
The star RZ Psc is one of the most unusual members of the UX Ori star family. It demonstrates all properties that are typical of these stars (the light variability, high linear polarization in deep minima, the blueing effect), but until recently there has been no obvious evidence of its youth. Recently, we have shown that RZ Psc is in the transitional evolutionary stage between stars with the primordial and debris disks. In this paper we present the results of the quantitative analysis of the star's spectrum. Using the high-resolution (R = 46 000) spectrum of RZ Psc obtained with Nordic Optical Telescope, we determined T eff = 5350 ± 150 K, log g = 4.2 ± 0.2, [M/H] = −0.3 ± 0.05. These parameters agree well with the same ones as for the stars recently passed the T Tauri star evolutionary stage. This supports our previous suggestion about the evolutionary status of RZ Psc as the post-T Tauri and post-UX Ori star.
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