Astronomy & Astrophysics

Free access article

A&A 427, 245-250 (2004)
DOI: 10.1051/0004-6361:20041502

Evolution of young brown dwarf disks in the mid-infrared

M. F. Sterzik¹, I. Pascucci², D. Apai², N. van der Bliek³ and C. P. Dullemond⁴

¹ European Southern Observatory, Casilla 19001, Santiago 19, Chile
e-mail: msterzik@eso.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

(Received 21 June 2004 / Accepted 30 August 2004)

Abstract
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 ( $\approx$ 2 Myr) Cha H $\alpha$ 1 we measure fluxes at 10.4 $\mu$ m and 12.3 $\mu$ m that are fully consistent with a standard flared disk model and prominent silicate emission. For the $\approx$ 10 Myr old brown dwarf 2MASS1207-3932 located in the TW Hydrae association we find excess emission at 8.7 $\mu$ m and 10.4 $\mu$ m 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

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