Modeling Brown Dwarf Atmospheres at the L/T Transition
Abstract
Substellar evolutionary models, dependent upon mass and age, predict cooling rates for brown dwarfs. Binary systems with directly measured quantities of dynamical mass and luminosity can be used to infer age and test the predictability of such evolutionary models. We are conducting a photometric and spectroscopy survey of the individual components in a sample of brown dwarf binaries by using adaptive optics and near-infrared instruments at the Keck Observatory. We use the PHOENIX atmosphere code to model the atmospheres of these objects in order to better characterize their properties (e.g., temperature, gravity, metallicity, and clouds). Traditional PHOENIX cloudy (Dusty) and cloud-free (Cond) model grids provide useful limits for the photometric and spectroscopic properties of brown dwarfs while also capturing some of the observed trends; however, these two limiting cases avoid most of the challenges associated with modeling the cloudy atmospheres of substellar objects. Clouds strongly influence the relationship between spectral morphology and effective temperature, and the L/T transition objects are notoriously difficult to interpret with overly restrictive and generalized assumptions about clouds. We are constructing individualized model grids for each of the brown dwarf binaries with a particular focus on cloud properties for objects having effective temperatures between 1200 and 1400 K. We present new comparisons between predictions from evolutionary models and properties determined solely from atmosphere model fitting.
- Publication:
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American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23325918B