Program: GN-2013A-Q-21

Recently WISE discovered the local population of cold Y dwarfs. New models calculated by members of our team which include chloride and sulfide clouds are successful at reproducing the energy distributions of brown dwarfs with T_eff between 400K and 800K (Y0 to T8 types). Below 400K the chloride and sulfide clouds clear, and water clouds will form. We propose a monitoring program using NIRI at 1um to search for variability in three 300 -- 400K Y dwarfs, on time scales of minutes, hours and months. The observations will be combined with 3.6 and 4.5um monitoring data from awarded Spitzer Cycle 9 time. We expect significant variability at 1um, as is seen at the L to T transition, mid-IR variability is also possible, based on Jupiter's 5um hotspots. The color, amplitude and timeframe of the variability will constrain both its cause and our models. We are working on models which include H2O clouds. The new model suite will enable detailed study of brown dwarfs and gas giant exoplanets at nearly all relevant T_eff, including those found at Gemini by GPI.