摘要：The binary T Tauri star V582 Mon (KH 15D) is surrounded by a tilted and nodally precessing ring of dusty material, which has caused periodic occultations of one or both stars over the last 50 years.Here, we present multi-color time-series photometry (VRIJHK) throughout the 2017/2018 observing season, when the ring was covering the entire orbit of star A and gradually exposing the orbit of star B.We calculate the mean apparent magnitude of star B to be I = 14.08.Besides the periodic eclipses of star B due to its orbital motion, we observed unexpected dips in brightness indicative of partially transparent stellar-sized clumps within the ring.The wavelength dependence of these events is suggestive of extinction by dust grains significantly larger than typical interstellar dust grains.The photometric variability observed while star B is being uncovered by the trailing edge of the ring is not simply the time reversal of the behavior seen when star A was being covered by the leading edge.Whereas the leading edge appeared to be very sharply defined, the trailing edge is "clumpy" and "fuzzy" (transparent), with a more gradual transition in opacity.The clumpiness and transparency of the occulting material provide a unique opportunity to study the properties of dust grains in a likely planet-forming zone.
关键词：Weak-line T Tauri stars;T Tauri stars;Binary stars;Protoplanetary disks
