CLOUD ATLAS: DISCOVERY of PATCHY CLOUDS and HIGH-AMPLITUDE ROTATIONAL MODULATIONS in A YOUNG, EXTREMELY RED L-TYPE BROWN DWARF

Ben W.P. Lew, Daniel Apai, Yifan Zhou, Glenn Schneider, Adam J. Burgasser, Theodora Karalidi, Hao Yang, Mark S. Marley, Nicolas B. Cowan, Luigi R. Bedin, Stanimir A. Metchev, Jacqueline Radigan, Patrick J. Lowrance

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-Ks=2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy, we find a best-fit rotational period (13.20±0.14 hr) with a larger amplitude at 1.1 μm than at 1.7 μm. This is the third-largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentative trend between the wavelength dependence of relative amplitude, possibly proxy for small dust grains lofted in the upper atmosphere, and the likelihood of large-amplitude variability. By assuming forsterite as a haze particle, we successfully explain the wavelength-dependent amplitude with submicron-sized haze particle sizes of around 0.4 μm. W0047 links the earlier spectral and later spectral type brown dwarfs in which rotational modulations have been observed; the large amplitude variations in this object make this a benchmark brown dwarf for the study of cloud properties close to the L/T transition.

Original languageEnglish (US)
Article numberL32
JournalAstrophysical Journal Letters
Volume829
Issue number2
DOIs
StatePublished - Oct 1 2016

Keywords

  • brown dwarfs
  • stars: atmospheres
  • stars: individual (WISEP J004701.06+680352.1)
  • stars: low-mass

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Lew, B. W. P., Apai, D., Zhou, Y., Schneider, G., Burgasser, A. J., Karalidi, T., Yang, H., Marley, M. S., Cowan, N. B., Bedin, L. R., Metchev, S. A., Radigan, J., & Lowrance, P. J. (2016). CLOUD ATLAS: DISCOVERY of PATCHY CLOUDS and HIGH-AMPLITUDE ROTATIONAL MODULATIONS in A YOUNG, EXTREMELY RED L-TYPE BROWN DWARF. Astrophysical Journal Letters, 829(2), [L32]. https://doi.org/10.3847/2041-8205/829/2/L32