Compositional indicators in infrared spectra of brown dwarfs

Temperature-pressure profiles in atmospheres of various compositions have been constructed for stellar objects ranging from a Jupiter mass up to 0.05 solar masses, and effective temperatures up to 2200K. These profiles are used (1) as boundary conditions to interior models and (2) to construct broad-band emergent infrared spectra of brown dwarfs. The author focuses on assessing the compositional information which can be derived from comparison of synthetic spectra with available or anticipated data on the infrared companion to VB8. Preliminary conclusions include (1) the shape of the infrared spectrum should be very sensitive to the elemental carbon-to-oxygen ratio in the envelope, (2) the effective temperature of VB8B must be close to the backbody temperature of 1360 K. (3) the presence of grain opacity in the envelope is hinted at by the available data. (author)