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arXiv · 1801.09757

Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B

Yifan Zhou·Dániel Apai·Stanimir Metchev·Ben W. P. Lew·Glenn Schneider·Mark S. Marley·Theodora Karalidi·Elena Manjavacas·Luigi R. Bedin·Nicolas B. Cowan·Paulo A. Miles-Páez·Patrick J. Lowrance·Jacqueline Radigan·Adam J. Burgasser
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Abstract

Time-resolved observations of brown dwarfs' rotational modulations provide powerful insights into the properties of condensate clouds in ultra-cool atmospheres. Multi-wavelength light curves reveal cloud vertical structures, condensate particle sizes, and cloud morphology, which directly constrain condensate cloud and atmospheric circulation models. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared G141 taken in six consecutive orbits observations of HN Peg B, an L/T transition brown dwarf companion to a G0V type star. The best-fit sine wave to the $1.1-1.7\mu$m broadband light curve has the amplitude of $1.206\pm0.025\%$ and period of $15.4\pm0.5$ hr. The modulation amplitude has no detectable wavelength dependence except in the 1.4 $\mu$m water absorption band, indicating that the characteristic condensate particle sizes are large ($>1\mu$m). We detect significantly ($4.4\sigma$) lower modulation amplitude in the 1.4$\mu$m water absorption band, and find that HN Peg B's spectral modulation resembles those of early T type brown dwarfs. We also describe a new empirical interpolation method to remove spectral contamination from the bright host star. This method may be applied in other high-contrast time-resolved observations with WFC3.

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Yifan Zhou, Dániel Apai, Stanimir Metchev, Ben W. P. Lew, Glenn Schneider, Mark S. Marley, Theodora Karalidi, Elena Manjavacas, Luigi R. Bedin, Nicolas B. Cowan, Paulo A. Miles-Páez, Patrick J. Lowrance, Jacqueline Radigan, Adam J. Burgasser. 2018-01-29. Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B. https://doi.org/10.3847/1538-3881%2Faaabbd

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