CaltechAUTHORS
Published October 1, 2019 | Version Submitted + Published
Journal Article Open

Cloud Atlas: Variability in and out of the Water Band in the Planetary-mass HD 203030B Points to Cloud Sedimentation in Low-gravity L Dwarfs

Creators

  • 1. ROR icon Western University
  • 2. ROR icon University of Arizona
  • 3. ROR icon American Museum of Natural History
  • 4. ROR icon NASA Exoplanet Science Institute
  • 5. ROR icon W.M. Keck Observatory
  • 6. ROR icon University of Central Florida
  • 7. ROR icon University of California, San Diego
  • 8. ROR icon Osservatorio Astronomico di Padova
  • 9. ROR icon McGill University
  • 10. ROR icon Infrared Processing and Analysis Center
  • 11. ROR icon Ames Research Center
  • 12. ROR icon Utah Valley University

Abstract

We use the Wide Field Camera 3 on the Hubble Space Telescope to spectrophotometrically monitor the young L7.5 companion HD 203030B. Our time series reveal photometric variability at 1.27 and 1.39 μm on timescales compatible with rotation. We find a rotation period of 7.5_(-0.5)^(+0.6) hr: comparable to those observed in other brown dwarfs and planetary-mass companions younger than 300 Myr. We measure variability amplitudes of 1.1% ± 0.3% (1.27 μm) and 1.7% ± 0.4% (1.39 μm), and a phase lag of 56° ± 28° between the two light curves. We attribute the difference in photometric amplitudes and phases to a patchy cloud layer that is sinking below the level where water vapor becomes opaque. HD 203030B and the few other known variable young late-L dwarfs are unlike warmer (earlier-type and/or older) L dwarfs, for which variability is much less wavelength-dependent across the 1.1–1.7 μm region. We further suggest that a sinking of the top-most cloud deck below the level where water or carbon monoxide gas become opaque may also explain the often enhanced variability amplitudes of even earlier-type low-gravity L dwarfs. Because these condensate and gas opacity levels are already well-differentiated in T dwarfs, we do not expect the same variability amplitude enhancement in young versus old T dwarfs.

Additional Information

© 2019. The American Astronomical Society. Received 2019 July 20; accepted 2019 August 19; published 2019 October 3. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555, under GO 14241. We are grateful for research support provided by the Natural Sciences and Engineering Research Council of Canada (grant No. RGPIN-04396-2014) and the Canada Research Chairs Program. Facilities: HST: (WFC3) - , Gaia. - Software: IRAF (Tody 1986, 1993), Corner plot (Foreman-Mackey 2016).

Attached Files

Published - Miles-Paez_2019_ApJ_883_181.pdf

Submitted - 1908-09403.pdf

Files

1908-09403.pdf

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Additional details

Identifiers

Eprint ID
99053
Resolver ID
CaltechAUTHORS:20191003-113815666

Related works

Describes
10.48550/arXiv.1908.09403 (DOI)

Funding

NASA
NAS 5-26555
NASA
GO 14241
Natural Sciences and Engineering Research Council of Canada (NSERC)
RGPIN-04396-2014
Canada Research Chairs Program

Dates

Created
2019-10-03
Created from EPrint's datestamp field
Updated
2023-10-02
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Infrared Processing and Analysis Center (IPAC)