LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES

By Jacqueline Radigan, R. Jayawardhana, D. Lafrèniere, É. Artigau, M. Marley, D. Saumon. 2012

171 citations recorded by the source corpus.

We present multiple-epoch photometric monitoring in the J, H, and Ks bands of the T1.5 dwarf 2MASS J21392676+0220226 (2M2139), revealing persistent, periodic (P = 7.721 ± 0.005 hr) variability with a peak-to-peak amplitude as high as 26% in the J band. The light curve shape varies on a timescale of days, suggesting that evolving atmospheric cloud features are responsible. Using interpolations between model atmospheres with differing cloud thicknesses to represent a heterogeneous surface, we find that the multi-wavelength variations and the near-infrared spectrum of 2M2139 can be reproduced by either (1) cool, thick cloud features sitting above a thinner cloud layer, or (2) warm regions of low condensate opacity in an otherwise cloudy atmosphere, possibly indicating the presence of holes or breaks in the cloud layer. We find that temperature contrasts between thick and thin cloud patches must be greater than 175 K and as high as 425 K. We also consider whether the observed variability could arise from an interacting binary system, but this scenario is ruled out. 2M2139 joins the T2.5 dwarf SIMP0136 discovered by Artigau and coworkers as the second L/T transition brown dwarf to display large-amplitude variability on rotational timescales, suggesting that the fragmentation of dust clouds at the L/T transition may contribute to the abrupt decline in condensate opacity and J-band brightening observed to occur over this regime.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/bd573e9e9a47be1fcb273f326f7ee6943c9aef46

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In Astronomy and Astrophysics

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

Citations in the corpus

• MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS (2012, background): “T transition dwarfs that vary in brightness with time with relatively large near-infrared amplitudes (Artigau et al. 2009; Radigan et al. 2012b).”
• On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets (2014, background): “Broadband observations have revealed periodic and non-periodic flux variations as large as 10–30% (Radigan et al. 2012; Gillon et al. 2013), occurring on timescales from 1–100 hr (Bailer-Jones & Mundt 2001), and spectroscopic observations have shown that variability can be strongly…”
• NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES (2012, background): “However, the recent discovery of highly photometrically variable early T dwarfs suggests that cloud patchiness may indeed play a role (Radigan et al. 2012; Artigau et al. 2009).”
• The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs (2020, background): “This object is now noted for its extreme variability (26% at J-band), leading Radigan et al. (2012) to conclude that the object’s variations were caused either by multi-layered clouds or a cloud layer with holes.”
• DISCOVERY OF A BINARY BROWN DWARF AT 2 pc FROM THE SUN (2013, background): “Thus, it may be an attractive target for de- tailed photometric monitoring (e.g., Artigau et al. 2009; Radigan et al. 2012).”
• HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS (2013, methodology): “…to consider the possibility that the fit by two blended spectra in this case is not the sign of an unresolved binary, but instead emerges from the blend of two different surface types on the source (as also proposed by Khandrika et al. 2013 and Radigan et al. 2012)— one with a spectrum of an L8.”
• WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “5 spectral binary candidate by Burgasser et al. (2010a), but identified as a J-band variable (Radigan et al. 2012) that is unresolved in HST images (Apai et al. 2013), and exhibits no radial velocity variations (Khandrika et al. 2013).”
• THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA (2015, background): “…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; Metchev et al. 2015).”