Mid-IR spectroscopy of T Tauri stars in Chamealeon I: Evidence for processed dust at the earliest stages

We present mid-IR spectroscopy of three T Tauri stars in the young Chamealeon I dark cloud obtained with TIMMI2 on the ESO 3.6 m telescope. In these three stars, the silicate emission band at 9.7 (mu)m is prominent. We model it with a mixture of amorphous olivine grains of different size, crystalline silicates and silica. The fractional mass of these various components change widely from star to star. While the spectrum of CR Cha is dominated by small amorphous silicates, in VW Cha (and in a lesser degree in Glass I), there is clear evidence of a large amount of processed dust in the form of crystalline silicates and large amorphous grains. This is the first time that processed dust has been detetected in very young T Tauri stars (~1 Myr).