Molecular Abundances in the Atmosphere of the T Dwarf Gl 229B

Saumon, D.; Geballe, T. R.; Leggett, S. K.; Marley, Mark S.; Freedman, Richard; Lodders, K.; Fegley, B.; Sengupta, Sujan

doi:10.1086/309410

Cited by 146 publications

(232 citation statements)

References 37 publications

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“…As a result, the peak-to-trough variation in emitted Ñux is again somewhat smaller for the cloudy model. We note that clear atmosphere models for T dwarfs such as Gl 229B and GD 165B typically overpredict the water band depths (e.g., Marley et al 1996 ;Allard et al 1996 ;Tsuji et al 1996 ;Saumon et al 2000 ;Geballe et al 2001) and suggest that the attenuation of Ñux by the top of the silicate cloud deck may be responsible for this e †ect. Notably, these model atmospheres illustrate the origin of the curious change in infrared colors of the L and T dwarfs (e.g., Kirkpatrick et al 1999 ;Fan et al Mart•n 2000).…”

Section: Ertical Cloud Structurementioning

confidence: 70%

Precipitating Condensation Clouds in Substellar Atmospheres

Ackerman

Marley

2001

ApJ

756

1,283

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We present a method to calculate vertical proÐles of particle size distributions in condensation clouds of giant planets and brown dwarfs. The method assumes a balance between turbulent di †usion and sedimentation in horizontally uniform cloud decks. Calculations for the Jovian ammonia cloud are compared with results from previous methods. An adjustable parameter describing the efficiency of sedimentation allows the new model to span the range of predictions made by previous models. Calculations for the Jovian ammonia cloud are consistent with observations. Example calculations are provided for water, silicate, and iron clouds on brown dwarfs and on a cool extrasolar giant planet. We Ðnd that precipitating cloud decks naturally account for the characteristic trends seen in the spectra of Land T-type ultracool dwarfs.

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Section: Ertical Cloud Structurementioning

confidence: 70%

Precipitating Condensation Clouds in Substellar Atmospheres

Ackerman

Marley

2001

ApJ

756

1,283

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“…tion is important when we consider the difficulty in estimating e †ective temperature from spectral data. These objects are clearly not blackbodies, and brightness temperatures derived from spectral data can range over 1000 K in the 1È2.5 km regime (Saumon et al 2000). However, a reasonable estimate of can be obtained if the total luminosity T eff of a degenerate brown dwarf is known.…”

Section: E †Ective T Emperaturesmentioning

confidence: 99%

“…These scales Mart•n clearly bracket the e †ective temperatures calculated here TABLE 17 Leggett et al (2001) are T eff indicated by triangles. The two Ðlled circles plot estimates for Gliese T eff 229B (Saumon et al 2000) and Gliese 570D (Burgasser et al 2000a ;Geballe et al 2001). Spectral type/e †ective temperature scales from Kirkpatrick et al (1999Kirkpatrick et al ( , 2000 and Basri et al (2000) are indicated, with the latter scale corrected to the Kirkpatrick et al (1999) spectral sequence.…”

Section: T He T Emperatures Of L Dwarfsmentioning

confidence: 99%

The Spectra of T Dwarfs. I. Near‐Infrared Data and Spectral Classification

Burgasser

Kirkpatrick

Brown

et al. 2002

ApJ

409

513

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We present near-infrared spectra for a sample of T dwarfs, including 11 new discoveries made using the 2 Micron All Sky Survey. These objects are distinguished from warmer (L-type) brown dwarfs by the presence of methane absorption bands in the 1È2.5 km spectral region. A Ðrst attempt at a near-infrared classiÐcation scheme for T dwarfs is made, based on the strengths of and bands and the CH 4 H 2 O shapes of the 1.25, 1.6, and 2.1 km Ñux peaks. Subtypes T1 VÈT8 V are deÐned, and spectral indices useful for classiÐcation are presented. The subclasses appear to follow a decreasing scale, based on T eff the evolution of and bands and the properties of L and T dwarfs with known distances. CH 4 H 2 O However, we speculate that this scale is not linear with spectral type for cool dwarfs, due to the settling of dust layers below the photosphere and subsequent rapid evolution of spectral morphology around K. Similarities in near-infrared colors and continuity of spectral features suggest that T eff D 1300È1500 the gap between the latest L dwarfs and earliest T dwarfs has been nearly bridged. This argument is strengthened by the possible role of as a minor absorber, shaping the K-band spectra of the latest CH 4 L dwarfs. Finally, we discuss one peculiar T dwarf, 2MASS 0937]2931, which has very blue nearinfrared colors due to suppression of the 2.1 km peak. The feature is likely (J [ K s \ [0.89^0.24) caused by enhanced collision-induced absorption in a high-pressure or low-metallicity photosphere. H 2

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“…Burrows et al (2001) presented a review of the substantial subsequent work devoted to understanding the properties of L and T dwarfs. Although the comparison of models to the spectra of individual objects such as Gl 229B (Saumon et al 2000) and Gl 570D (Geballe et al 2001;Saumon et al 2006) has played an important role in the progression of the field, relatively little work has been done on comparing entire classes of models to uniform data sets (see, however, Burgasser et al 2006a). Such comparisons are important, as they can reveal the global properties of a set of objects and highlight the systematic strengths and weaknesses of the models.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Parameters of Field L and T Dwarfs1

Cushing

Marley

Saumon

et al. 2008

ApJ

Self Cite

310

448

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We present an analysis of the 0.95Y14.5 m spectral energy distributions of nine field ultracool dwarfs with spectral types ranging from L1 to T4.5. Effective temperatures, gravities, and condensate cloud sedimentation efficiencies are derived by comparing the data to synthetic spectra computed from atmospheric models that self-consistently include the formation of condensate clouds. Overall, the model spectra fit the data well, although the agreement at some wavelengths remains poor due to remaining inadequacies in the models. Derived effective temperatures decrease steadily through the L1YT4.5 spectral types, and we confirm that the effective temperatures of ultracool dwarfs at the L/T transition are nearly constant, decreasing by only $200 K from spectral types L7.5 to T4.5. The condensate cloud properties vary significantly among the L dwarfs in our sample, ranging from very thick clouds to relatively thin clouds with no particular trend with spectral type. The two objects in our sample with very red J À K s colors are, however, best fitted with synthetic spectra that have thick clouds, which hints at a possible correlation between the near-infrared colors of L dwarfs and the condensate cloud properties. The fits to the two T dwarfs in our sample (T2 and T4.5) also suggest that the clouds become thinner in this spectral class, in agreement with previous studies. Restricting the fits to narrower wavelength ranges (i.e., individual photometric bands) almost always yields excellent agreement between the data and models. Limitations in our knowledge of the opacities of key absorbers such as FeH, VO, and CH 4 at certain wavelengths remain obvious, however. The effective temperatures obtained by fitting the narrower wavelength ranges can show a large scatter compared to the values derived by fitting the full spectral energy distributions; deviations are typically $200 K and, in the worst cases, up to 700 K.

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Molecular Abundances in the Atmosphere of the T Dwarf Gl 229B

Cited by 146 publications

References 37 publications

Precipitating Condensation Clouds in Substellar Atmospheres

Precipitating Condensation Clouds in Substellar Atmospheres

The Spectra of T Dwarfs. I. Near‐Infrared Data and Spectral Classification

Atmospheric Parameters of Field L and T Dwarfs1

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