Indications of Water Clouds in the Coldest Known Brown Dwarf

Abstract

We present a deep near-infrared image of the newly discovered brown dwarf WISE J085510.83-071442.5 (W0855) using the FourStar imager at Las Campanas Observatory. Our detection of J3=24.8+0.33 -0.53 (J_MKO=25.0+0.33-0.53) at 2.6sigma -- or equivalently an upper limit of J3 > 23.8 (J_MKO > 24.0) at 5sigma makes W0855 the reddest brown dwarf ever categorized (J_MKO - W2 = 10.984+0.33 - 0.53 at 2.6sigma -- or equivalently an upper limit of J_MKO - W2 > 9.984 at 5sigma) and refines its position on color magnitude diagrams. Comparing the new photometry with chemical equilibrium model atmosphere predictions, we demonstrate that W0855 is 4.5sigma from models using a cloudless atmosphere and well reproduced by partly cloudy models (50%) containing sulfide and water ice clouds. Non-equilibrium chemistry or non-solar metallicity may change predictions, however using currently available model approaches, this is the first candidate outside our own solar system to have direct evidence for water clouds.

Accepted for publication in ApJ Letters. Eight pages, 3 Figures

References in corpus (4)

• Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun
• Spitzer/IRAC Photometry of M, L, and T Dwarfs
• Water Clouds in Y Dwarfs and Exoplanets
• A Systematic Study of Departures from Chemical Equilibrium in the Atmospheres of Substellar Mass Objects

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