Characterizing the disk around the TW Hydrae Association brown dwarf 2MASSW J1207334-393254

Abstract

We present detailed modeling of the disk around the TW Hydrae Association (TWA) brown dwarf 2MASSW J1207334 - 393254 (2M1207), using Spitzer observations from 3.6 to 24 mu m. The spectral energy distribution (SED) does not show a high amount of flaring. We have obtained a good fit using a flat disk of mass between 10(-4) and 10(-6) M-circle dot, M less than or similar to 10(-11) M-circle dot yr(-1), and a large inclination angle between 60 degrees and 70 degrees. We have used three different grain models to fit the 10 mu m Si emission feature, and have found the results to be consistent with ISM-like dust. In comparison with other TWA members, this suggests lesser dust processing for 2M1207, which could be explained by mechanisms such as aggregate fragmentation and/or turbulent mixing. We have found a good fit using an inner disk radius equal to the dust sublimation radius, which indicates the absence of an inner hole in the disk. This suggests the presence of a small K - L' excess, similar to the observed K - [3.6] excess.