Modeling the Formation of Clouds in Brown Dwarf Atmospheres
- 1 April 2003
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 586 (2), 1320-1337
- https://doi.org/10.1086/367763
Abstract
Because the opacity of clouds in substellar mass object (SMO) atmospheres depends on the composition and distribution of particle sizes within the cloud, a credible cloud model is essential for accurately modeling SMO spectra and colors. We present a one-dimensional model of cloud particle formation and subsequent growth based on a consideration of basic cloud microphysics. We apply this microphysical cloud model to a set of synthetic brown dwarf atmospheres spanning a broad range of surface gravities and effective temperatures (g(surf) = 1.78 x 10(3)-3 x 10(5) cm s(-2) and T-eff = 600-1600 K) to obtain plausible particle sizes for several abundant species (Fe, Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are largest, the particle sizes thus computed range from similar to5 to over 300 mum in radius over the full range of atmospheric conditions considered. We show that average particle sizes decrease significantly with increasing brown dwarf surface gravity. We also find that brown dwarfs with higher effective temperatures have characteristically larger cloud particles than those with lower effective temperatures. We therefore conclude that it is unrealistic when modeling SMO spectra to apply a single particle size distribution to the entire class of objects.Keywords
Other Versions
This publication has 28 references indexed in Scilit:
- The theory of brown dwarfs and extrasolar giant planetsReviews of Modern Physics, 2001
- Precipitating Condensation Clouds in Substellar AtmospheresThe Astrophysical Journal, 2001
- Irradiated PlanetsThe Astrophysical Journal, 2001
- The Limiting Effects of Dust in Brown Dwarf Model AtmospheresThe Astrophysical Journal, 2001
- Variability in ultra cool dwarfs: Evidence for the evolution of surface featuresAstronomy & Astrophysics, 2001
- Observations of Brown DwarfsAnnual Review of Astronomy and Astrophysics, 2000
- Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet AtmospheresThe Astrophysical Journal, 1999
- Theoretical models of very low mass stars and brown dwarfsThe Astrophysical Journal, 1989
- Abundances of the elements: Meteoritic and solarGeochimica et Cosmochimica Acta, 1989
- Chemistry of Primitive Solar MaterialAnnual Review of Astronomy and Astrophysics, 1976