  We present accurate mid-infrared observations of the disk around the young,
bona-fide brown dwarf CFHT-BD-Tau 4. We report GEMINI/T-ReCS measurements in
the 7.9, 10.4 and 12.3 micron filters, from which we infer the presence of a
prominent, broad silicate emission feature. The shape of the silicate feature
is dominated by emission from 2 micron amorphous olivine grains. Such grains,
being an order of magnitude larger than those in the interstellar medium, are a
first proof of dust processing and grain growth in disks around brown dwarfs.
The object's spectral energy distribution is below the prediction of the
classical flared disk model but higher than that of the two-layer flat disk. A
good match can be achieved by using an intermediate disk model with strongly
reduced but non-zero flaring. Grain growth and dust settling processes provide
a natural explanation for this disk geometry and we argue that such
intermediate flaring might explain the observations of several other brown
dwarf disks as well.

Astrophysics