PI: Jacqueline Radigan, University of Toronto, firstname.lastname@example.org
Address: Astronomy Department, 50 St George Street, Toronto, Ontario M5S 3H4, Canada
CoI: Ray Jayawardhana, University of Toronto
CoI: David Lafreniere, University of Toronto
Title: Complementary Keck LGS AO Observations of T-dwarfs Targeted in a Variability Monitoring Program
Abstract: One of the most puzzling behaviors exhibited by cool brown dwarfs (BDs) is their rapid evolution from very red (J-K~2) to very blue (J-K~0) near infrared colors at the boundary between L and T spectral types, marking the transition from cloudy to cloud-free atmospheres. It has been suggested that this rapid evolution is caused by the sudden fragmentation of cloud decks above the photosphere. We are conducting a monitoring program of ~ 50 late-type BDs for rotationally modulated variability in order to test this hypothesis. However, due to the rapidity of the L/T transition, it has been suggested that the majority of so-called transition BDs are actually the spurious result of unresolved binarity. This hidden binarity greatly complicates the interpretation of variability studies. Therefore, we are proposing to observe a subsample of early T-dwarf targets with intermediate NIR colors (0.3<J-K<1.4) from our variability monitoring program, using the LGS AO system at Keck. These observations are intended to differentiate between single T-dwarfs in our sample whose intrinsic NIR colors bridge the L/T transition, versus binaries whose NIR colors arise from the superposition of two sources.
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