Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data

Adam Burrows, Adam J. Burgasser, J. Davy Kirkpatrick, James Liebert, J. A. Milsom, D. Sudarsky, Ivan - Hubeny

Research output: Contribution to journalArticle

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Abstract

We have generated new, self-consistent spectral and atmosphere models for the effective temperature range 600-1300 K thought to encompass the known T dwarfs. For the first time, theoretical models are compared with a family of measured T dwarf spectra at wavelengths shortward of ∼ 1.0 μm. By defining spectral indices and standard colors in the optical and very near-infrared, we explore the theoretical systematics with Teff, gravity, and metallicity. We conclude that the short-wavelength range is rich in diagnostics that complement those in the near-infrared now used for spectral subtyping. We also conclude that the wings of the Na D and K I (7700 Å) resonance lines and aggressive rainout of heavy metals (with the resulting enhancement of the sodium and potassium abundances at altitude) are required to fit the new data shortward of 1.0 μm. Furthermore, we find that the water bands weaken with increasing gravity, that modest decreases in metallicity enhance the effect in the optical of the sodium and potassium lines, and that at low values of Teff, in a reversal of the normal pattern, optical spectra become bluer with further decreases in Teff. Moreover, we conclude that T dwarf subtype is not a function of Teff alone but that it is a nontrivial function of gravity and metallicity as well. As do Marley and coworkers in their 2002 work, we see evidence in early T dwarf atmospheres of a residual effect of clouds. With cloudless models, we obtain spectral fits to the two late T dwarfs with known parallaxes, but a residual effect of clouds on the emergent spectra of even late T dwarfs cannot yet be discounted. However, our focus is not on detailed fits to individual objects but on the interpretation of the overall spectral and color trends of the entire class of T dwarfs, as seen at shorter wavelengths.

Original languageEnglish (US)
Pages (from-to)394-417
Number of pages24
JournalAstrophysical Journal
Volume573
Issue number1 I
DOIs
StatePublished - Jul 1 2002
Externally publishedYes

Fingerprint

metallicity
gravity
gravitation
wavelength
potassium
near infrared
sodium
wavelengths
color
atmospheres
atmosphere
heavy metals
resonance lines
wings
complement
optical spectrum
heavy metal
trends
augmentation
water

Keywords

  • Brown dwarfs
  • Infrared: stars
  • Stars: atmospheres
  • Stars: fundamental parameters
  • Stars: low mass
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Burrows, A., Burgasser, A. J., Kirkpatrick, J. D., Liebert, J., Milsom, J. A., Sudarsky, D., & Hubeny, I. . (2002). Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data. Astrophysical Journal, 573(1 I), 394-417. https://doi.org/10.1086/340584

Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data. / Burrows, Adam; Burgasser, Adam J.; Kirkpatrick, J. Davy; Liebert, James; Milsom, J. A.; Sudarsky, D.; Hubeny, Ivan -.

In: Astrophysical Journal, Vol. 573, No. 1 I, 01.07.2002, p. 394-417.

Research output: Contribution to journalArticle

Burrows, A, Burgasser, AJ, Kirkpatrick, JD, Liebert, J, Milsom, JA, Sudarsky, D & Hubeny, I 2002, 'Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data', Astrophysical Journal, vol. 573, no. 1 I, pp. 394-417. https://doi.org/10.1086/340584
Burrows A, Burgasser AJ, Kirkpatrick JD, Liebert J, Milsom JA, Sudarsky D et al. Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data. Astrophysical Journal. 2002 Jul 1;573(1 I):394-417. https://doi.org/10.1086/340584
Burrows, Adam ; Burgasser, Adam J. ; Kirkpatrick, J. Davy ; Liebert, James ; Milsom, J. A. ; Sudarsky, D. ; Hubeny, Ivan -. / Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data. In: Astrophysical Journal. 2002 ; Vol. 573, No. 1 I. pp. 394-417.
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