Volume 427, Number 1, November III 2004
|Page(s)||245 - 250|
|Section||Interstellar and circumstellar matter|
|Published online||25 October 2004|
Evolution of young brown dwarf disks in the mid-infrared
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: firstname.lastname@example.org
2 Max-Planck Institute für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
3 Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
4 Max-Planck Institute für Astrophysik, Postfach 1317, 85748 Garching bei München, Germany
Accepted: 30 August 2004
We have imaged two bona-fide brown dwarfs with TReCS/GEMINI-S and find mid-infrared excess emission that can be explained by optically thick dust disk models. In the case of the young (≈2 Myr) Cha Hα1 we measure fluxes at 10.4 μm and 12.3 μm that are fully consistent with a standard flared disk model and prominent silicate emission. For the ≈10 Myr old brown dwarf 2MASS1207-3932 located in the TW Hydrae association we find excess emission at 8.7 μm and 10.4 μm with respect to the photosphere, and confirm disk accretion as a likely cause of its strong activity. Disks around brown dwarfs likely last at least as long as their low-mass stellar counterparts in the T-Tauri phase. Grain growth, dust settling, and evolution of the geometry of brown dwarf disks may appear on a timescale of 10 Myr and can be witnessed by observations in the mid-infrared.
Key words: accretion, accretion disks / stars: low-mass, brown dwarfs / stars: formation
© ESO, 2004
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