Evidence of Cloud Disruption in the L/T Dwarf Transition

By A. Burgasser, M. Marley, Andrew S. Ackerman, D. Saumon, K. Lodders, C. Dahn, Hugh C. Harris, J. D. Kirkpatrick. 2002

200 citations recorded by the source corpus.

Clouds of metal-bearing condensates play a critical role in shaping the emergent spectral energy distributions of the coolest classes of low-mass stars and brown dwarfs, L and T dwarfs. Because condensate clouds in planetary atmospheres show distinct horizontal structure, we have explored a model for partly cloudy atmospheres in brown dwarfs. Our model successfully reproduces the colors and magnitudes of both L and T dwarfs for the first time, including the unexpected brightening of the early- and mid-type T dwarfs at the J band, provided that clouds are rapidly removed from the photosphere at Teff ≈ 1200 K. The clearing of cloud layers also explains the surprising persistence and strengthening of gaseous FeH bands in early- and mid-type T dwarfs. The breakup of cloud layers is likely driven by convection in the troposphere, analogous to phenomena observed on Jupiter. Our results demonstrate that planetary-like atmospheric dynamics must be considered when examining the evolution of free-floating brown dwarfs.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2e268678effb6ee06a01556720ecb0b5bb36bf17

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In Astronomy and Astrophysics

1. A. Burgasser
2. Michael C. Liu
3. M. Marley
4. J. D. Kirkpatrick
5. T. Dupuy
6. K. Luhman
7. Jon Fortney
8. Kelle Cruz

In Instrumentation

1. A. Burgasser
2. Michael C. Liu
3. J. D. Kirkpatrick
4. T. Dupuy
5. M. Marley
6. K. Luhman
7. Kelle Cruz
8. Jon Fortney

Citations in the corpus

• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey (2006, methodology): “…(Fan et al. 1999, 2000b, 2001a, 2001b, 2003, 2004; Zheng et al. 2000) to the faintest and nearest stars and brown dwarfs (Kirkpatrick et al. 1999, 2000; Burgasser et al. 1999, 2002b; Fan et al. 2000a; Leggett et al. 2000; Geballe et al. 2002, hereafter G02; Knapp et al. 2004, hereafter K04).”
• New spectral types L and T (2005, methodology): “5-T0 (optical/near-infrared mismatch noted by Cruz et al. 2003; duplicity noted by Burgasser, priv. comm.), and 2MASS J0937 + 2931 at T6-T7 (spectroscopic peculiarity noted by Burgasser et al. 2002a).”
• A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs (2005, background): “These sources, the L dwarfs (Kirkpatrick et al. 1999; Mart́ın et al. 1999) and the T dwarfs (Burgasser et al. 2002a; Geballe et al. 2002, hereafter B02 and G02, respectively), lie beyond the standard stellar main sequence.”
• An Infrared Spectroscopic Sequence of M, L, and T Dwarfs (2004, methodology): “The strengthening of theK i lines in the early T dwarfs was originally noted by Burgasser et al. (2002b), who ascribed the behavior to the competing effects of decreasing effective temperature and loss of cloud opacity.”
• Dust in brown dwarfs - III. Formation and structure of quasi-static cloud layers (2004, unknown): “The formation and precipitation of dust particles has furthermore been suggested to cause the observed evolutionary sequence from L to T dwarfs, which change their J−K colour from red to blue with increasing age (Kirkpatick et al. 1999; Marley et al. 2002; Burgasser et al. 2002).”
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity (2004, methodology): “Indeed, Burgasser et al. (2002b) found that a relatively small fraction of holes would appreciably move a late L-type object toward the blue in J K.”
• NEAR-INFRARED SPECTROSCOPY OF THE EXTRASOLAR PLANET HR 8799 b (2010, background): “Our spectroscopic and photometric analysis indicates that the spectral type for HR 8799 b falls in the late-L/early-T range, corresponding to a physical regime where the atmospheres of field dwarfs are progressing from cloud-filled to cloudless (Burgasser et al. 2002).”
• LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, background): “Although a larger sample is needed, observations of 2M2139 and SIMP0136 suggest that large amplitude NIR variability may be more common at the L/T transition, consistent with the cloud fragmentation hypothesis of Ackerman & Marley (2001) and Burgasser et al. (2002).”
• Hubble Space Telescope Observations of Binary Very Low Mass Stars and Brown Dwarfs (2003, background): “…Skrutskie et al. 1997; Cutri et al. 2000),3 and Sloan Digital Sky Survey (SDSS; York et al. 2000) have enabled the discovery of numerous cool dwarfs and led to the definition of new spectral types L (Kirkpatrick et al. 1999; Martı́n et al. 1999b) and T (Burgasser et al. 2002a; Geballe et al. 2002).”
• Discovery of Two T Dwarf Companions with the Spitzer Space Telescope (2006, background): “Another possible explanation is photometric variability between the dates of the IRAC and JHK observations (Burgasser et al. 2002; Enoch et al. 2003).”
• THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, background): “…the late-L and early-T dwarfs, including non-equilibrium (dynamic) processes such rapid particle growth/sedimentation (Knapp et al. 2004; Stephens et al. 2009) and cloud disruption leading to spatially inhomogeneous photospheres (Ackerman & Marley 2001; Burgasser et al. 2002; Marley et al. 2010).”
• Binaries and the L Dwarf/T Dwarf Transition (2006, methodology): “…& Marley 2001; Cooper et al. 2003; Tsuji &Nakajima 2003; Burrows et al. 2006), so dynamical (nonequilibrium) processes such as cloud fragmentation (Burgasser et al. 2002a), a change in condensate sedimentation efficiency (Knapp et al. 2004), and a global collapse of the condensate cloud layer…”
• THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA (2015, background): “Similar processes are presumed to happen in Brown dwarf atmospheres (Burgasser et al. 2002; Marley et al. 2010; Zhang & Showman 2014), where observations are strongly suggestive of non-uniform cloud cover (Buenzli et al. 2012;14; Radigan et al. 2012;14; Crossfield et al. 2014; Apai et al. 2013;…”
• NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES (2012, background): “…when it reaches an effective temperature of approximately 1400 K. Objects cooler than this transitional effective temperature beginto show methane absorption features in their near-infrared spctra and, when these features appear, are classified as T dwarfs (Burgasser et al. 2002; Kirkpatrick 2005).”
• Atmospheric Chemistry in Giant Planets, Brown Dwarfs, and Low-Mass Dwarf Stars. II. Sulfur and Phosphorus (2005, background): “This makes SiS a potential tracer of weather in Pegasi planets and L dwarfs, analogous to FeH in T dwarfs (Burgasser et al. 2002), and gaps in the Mg-silicate cloud layers may expose regions where SiS is relatively abundant.”
• The Spectra of T Dwarfs. II. Red Optical Data (2003, background): “Current classification schemes for the two latest spectral classes, L dwarfs (Kirkpatrick et al. 1999; Martı́n et al. 1999) and T dwarfs (Burgasser et al. 2002c, hereafter Paper I; Geballe et al. 2002), are defined in different spectral regions.”
• A PATCHY CLOUD MODEL FOR THE L TO T DWARF TRANSITION (2010, methodology): “Burgasser et al. (2002) tested this hypothesis with a simple ‘toy model’ by summing weighted contributions of the spectra of cloudy and cloudless models.”