Evidence of Cloud Disruption in the L/T Dwarf Transition

June 2002 • 2002ApJ...571L.151B

Authors • Burgasser, Adam J. • Marley, Mark S. • Ackerman, Andrew S. • Saumon, Didier • Lodders, Katharina • Dahn, Conard C. • Harris, Hugh C. • Kirkpatrick, J. Davy

Abstract • Clouds of metal-bearing condensates play a critical role in shaping the emergent spectral energy distributions of the coolest classes of low-mass stars and brown dwarfs, L and T dwarfs. Because condensate clouds in planetary atmospheres show distinct horizontal structure, we have explored a model for partly cloudy atmospheres in brown dwarfs. Our model successfully reproduces the colors and magnitudes of both L and T dwarfs for the first time, including the unexpected brightening of the early- and mid-type T dwarfs at the J band, provided that clouds are rapidly removed from the photosphere at Teff~1200 K. The clearing of cloud layers also explains the surprising persistence and strengthening of gaseous FeH bands in early- and mid-type T dwarfs. The breakup of cloud layers is likely driven by convection in the troposphere, analogous to phenomena observed on Jupiter. Our results demonstrate that planetary-like atmospheric dynamics must be considered when examining the evolution of free-floating brown dwarfs.


IPAC Authors


Davy Kirkpatrick

Senior Scientist