The Limiting Effects of Dust in Brown Dwarf Model Atmospheres

Details The Limiting Effects of Dust in Brown Dwarf Model Atmospheres The Limiting Effects of Dust in Brown Dwarf Model Atmospheres

2001-04-16

arxiv.org/abs/astro-ph/0104256v2

Astrophys.J.556:357,2001

Astronomy and Astrophysics

Astrophysics

49 pages, ApJ, in press. 22 figures (included). Corrected nasty typos. Also available at http:/phoenix.physast.uga.edu

Scientific paper

10.1086/321547

We present opacity sampling model atmospheres, synthetic spectra and colors for brown dwarfs and very low mass stars in two limiting case of dust grain formation: 1) inefficient gravitational settling i.e. the dust is distributed according to the chemical equilibrium predictions, 2) efficient gravitational settling i.e. the dust forms and depletes refractory elements from the gas, but their opacity does not affect the thermal structure. The models include the formation of over 600 gas phase species, and 1000 liquids and crystals, and the opacities of 30 different types of grains including corundum (Al$_2$O$_3$), the magnesium aluminum spinel MgAl$_2$O$_4$, iron, enstatite (MgSiO$_3$), forsterite (Mg$_2$SiO$_4$), amorphous carbon, SiC, and a number of calcium silicates. The models extend from the beginning of the grain formation regime well into the condensation regime of water ice ($\teff= 3000 - 100$ K) and encompasses the range of $\log g= 2.5 - 6.0$ at solar metallicity. We find that silicate dust grains can form abundantly in the outer atmospheric layers of red and brown dwarfs with spectral type later than M8. The greenhouse effects of dust opacities provide a natural explanation for the peculiarly red spectroscopic distribution of the latest M dwarfs and young brown dwarfs. The grainless (Cond) models on the other hand, correspond closely to methane brown dwarfs such as Gliese 229B. We also recover that the $\lambda$5891,5897\AA Na I D and $\lambda$7687,7701\AA K I resonance doublets plays a critical role in T dwarfs where their red wing define the pseudo-continuum from the $I$ to the $Z$ bandpass.

Affiliated with

Also associated with

No associations

Rating

The Limiting Effects of Dust in Brown Dwarf Model Atmospheres does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Limiting Effects of Dust in Brown Dwarf Model Atmospheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Limiting Effects of Dust in Brown Dwarf Model Atmospheres will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-683580