The Atmospheric Retrieval of the Brown Dwarf Gl229B

Brown dwarfs that are found widely separated from main sequence stars are critical benchmarks for grounding our understanding of the fundamental properties of substellar mass objects. The main sequence star can anchor metallicity, age, and abundance measurements for the brown dwarf where such parameters are extremely difficult to probe. In this presentation, we present results from applying the spectral inversion technique to the brown dwarf Gl 229B using the retrieval code Brewster. Such atmospheric retrieval codes allow us to probe atmospheric abundances and speculate on bulk abundances. We can also improve upon previous grid models’ estimates of fundamental parameters such as log g, Teff, mass and radius. We use the near-infrared spectrum of Gl 229B between 1.0 μm and 2.5 μm to extrapolate retrieved thermal, chemical and cloud profiles so that we may compare such fundamental parameters with those previously estimated using grid models. We discuss the results and implications of cloud-free and cloudy models on this spectrum. In particular, we find a best fit model suggesting the presence of an optically thin cloud at low optical depth, despite previous literature suggesting the use of cloud-free models to best fit the observed spectrum.