Zones, spots, and planetary-scale waves beating in brown dwarf atmospheres

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Science  18 Aug 2017:
Vol. 357, Issue 6352, pp. 683-687
DOI: 10.1126/science.aam9848
  • Fig. 1 Spitzer Ch1 (3.6 μm) light curves for three brown dwarfs (blue points).

    (A to G) Our analytical three-wave models fit is overlain (black line) for each visit. (G) An example in which two waves with slightly different apparent periods result in a beat pattern. (H) The residuals reveal a single spot appearing four times during our observations as the brown dwarf rotated. The Ch2 (4.5 μm) data points (red points) sometimes, but not always, match the same model as the Ch1 data. The data gap at 1.1 to 1.25 days is due to spacecraft data download. Bars marked “In Fit” indicate data that are included in the analytical fit, chosen to exclude regions affected by spots (gaps labeled as “Spot”).

  • Fig. 2 The two key features (bands and spots) included in our light curve models and their appearance in the disk-integrated light curves.

    (A and B) Atmosphere models. (C and D) Disk-integrated light curves. Bands with zonal sinusoidally modulated surface brightness result in a sinusoidal temporal modulation in the light curve, whereas bright elliptical spots result in localized bright features. (E) The morphology of cloud features in Neptune observed in scattered near-infrared light (supplementary text). (F) Our best-fitting model of 2M1324 during visit 6.

  • Fig. 3 Probability distributions and power spectra for the brown dwarfs and Neptune.

    (A) Probability distributions for the model periods of the sinusoidally modulated bands for the three L/T transition brown dwarfs and the combined probability for 2M1324 and 2M2139 (bottom right) from all our visits (single-visit fits). Data are from the analytical fits, and each period is represented as a Gaussian, with the estimated period uncertainty as its width. The distributions show wave pairs and a half period wave (k = 2 wave) in 2M2139 and 2M1324 and an apparently single band and a half period band in the short-period S0136. (B) Power spectra representative of the slower-rotating T2 dwarfs (2M1324 and 2M2139, shown as a product) and for Neptune [from (18)], extracted from Kepler optical photometry probing scattered light. The power spectra display similar peak distributions, once the lower time-resolution and sensitivity of the brown dwarf observations are taken into account.

  • Fig. 4 MCMC model for 2M1324 visit 6.

    A Markov Chain Monte Carlo surface brightness model using Aeolus was fitted to the evolving light curve by using three sinusoidally modulated bands and a bright spot. The best-fitting model is very similar to our analytical model. The prominent light curve evolution is dominated by the beating effect caused by the phase shift between two modulations with slightly different periods. The four disks show the hemisphere facing the observer at the times corresponding to the center of each disk.

Supplementary Materials

  • Zones, spots, and planetary-scale waves beating in brown dwarf atmospheres

    D. Apai, T. Karalidi, M. Marley, H. Yang, D. Flateau, S. Metchev, N. B. Cowan, E. Buenzli, A. Burgasser, J. Radigan, E. Artigau, P. Lowrance

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Supplementary Text 
    • Figs. S1 to S15 
    • Tables S1 and S2 
    • References

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