Cited by 1,062Stellar, planetary, and galactic studiesAstrophysics and Star Formation StudiesAstro and Planetary Science

The Limiting Effects of Dust in Brown Dwarf Model Atmospheres

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Allard, France, Hauschildt, Peter H., Alexander, David R., Tamanai, Akemi, Schweitzer, Andreas·2001·The Astrophysical Journal

Abstract

We present opacity sampling model atmospheres, synthetic spectra, and colors for brown dwarfs and very low mass stars in the following two limiting cases of dust grain formation: (1) Inefficient gravitational settling (i.e., the dust is distributed according to the chemical equilibrium predictions) and (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 ( T eff = 3000-100 K) and encompass 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 a 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 discover that the λλ5891, 5897 Na I D and λλ7687, 7701 K I resonance doublets play a critical role in T dwarfs, in which their red wings define the pseudocontinuum from the I to the Z bandpass.

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Research works printed but not linked: 9

  1. [1]1. Ackerman, A., & Marley, M. 2001, ApJ, in press
  2. [5]5. Allard, F. 1990, Ph.D. thesis, Univ. Heidelberg ÈÈÈ. 1995, Nature, 378, 441
  3. [6]6. ÈÈÈ. 1998, in ASP Conf. Ser. 134, Brown Dwarfs and Extrasolar Planets, ed. R. Rebolo, E. L. & M. R. Zapatero Osorio (San Mart• n, Francisco : ASP), 370
  4. [7]7. Allard, F., Alexander, D. R., & Hauschildt, P. H. 1998a, in ASP Conf. Ser. 154, Cool Stars, Stellar Systems, and the Sun, ed. R. A. Donahue & J. A. Bookbinder (San Francisco : ASP), 63
  5. [8]8. Allard, F., Alexander, D. R., Tamanai, A., & Hauschildt, P. H. 1998b, in ASP Conf. Ser. 134, Brown Dwarfs and Extrasolar Planets, ed.
  6. [16]16. Barman, T. S., Hauschildt, P. H., & Allard, F. 2001, ApJ, in press
  7. [45]45. Griffith, C. A., & Yelle, R. V. 2000, Science, 282 (5396), 2063
  8. [97]97. Schweitzer, A., Gizis, J. E., Hauschildt, P. H., Allard, F., & Reid, I. N. 2001, ApJ, in press
  9. [106]106. ÈÈÈ. 1995, in ESO Astrophys. Symp. : The Bottom of the Main Sequence and Beyond, ed. C. Tinney (Berlin Springer), 45

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Authors
Allard, F., Hauschildt, P. H., Alexander, D. R., Tamanai, A., & Schweitzer, A.
Affiliations
  • École Normale Supérieure de Lyon (FR)
  • University of Georgia (US)
  • Wichita State University (US)
Venue
The Astrophysical Journal
Published
2001-07-20
Volume
556
Issue
1
Pages
357-372
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
OpenAlex
W2001265656
Cited by
1,062
References
97
Citations by year
2026: 22 · 2025: 34 · 2024: 34 · 2023: 29 · 2022: 25 · 2021: 46 · 2020: 42 · 2019: 39 · 2018: 53 · 2017: 38 · 2016: 49 · 2015: 52 · 2014: 44 · 2013: 68 · 2012: 44
FWCI
26.22
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • National Science Foundation
  • National Aeronautics and Space Administration (NAG58425, NAG53435)
  • Wichita State University
  • San Diego Supercomputer Center
  • Centre National de la Recherche Scientifique
  • Office of Experimental Program to Stimulate Competitive Research
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysics and Star Formation Studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
Keywords
brown dwarfs, very low mass stars, dust formation, gravitational settling, opacity, model atmospheres, silicate dust grains, greenhouse effect, T dwarfs, M dwarfs, Na I D lines, synthetic spectra, color

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