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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

Miles-Páez, Paulo A. and Metchev, Stanimir and Apai, Dániel and Zhou, Yifan and Manjavacas, Elena and Karalidi, Theodora and Lew, Ben W. P. and Burgasser, Adam J. and Bedin, Luigi R. and Cowan, Nicolas and Lowrance, Patrick J. and Marley, Mark S. and Radigan, Jacqueline and Schneider, Glenn (2019) 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. Astrophysical Journal, 883 (2). Art. No. 181. ISSN 1538-4357. doi:10.3847/1538-4357/ab3d25.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Miles-Páez, Paulo A.0000-0003-2446-8882
Metchev, Stanimir0000-0003-3050-8203
Apai, Dániel0000-0003-3714-5855
Zhou, Yifan0000-0003-2969-6040
Manjavacas, Elena0000-0003-0192-6887
Karalidi, Theodora0000-0001-7356-6652
Lew, Ben W. P.0000-0003-1487-6452
Burgasser, Adam J.0000-0002-6523-9536
Bedin, Luigi R.0000-0003-4080-6466
Cowan, Nicolas0000-0001-6129-5699
Lowrance, Patrick J.0000-0001-8014-0270
Marley, Mark S.0000-0002-5251-2943
Radigan, Jacqueline0000-0002-6732-3651
Schneider, Glenn0000-0002-4511-5966
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).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
NASAGO 14241
Natural Sciences and Engineering Research Council of Canada (NSERC)RGPIN-04396-2014
Canada Research Chairs ProgramUNSPECIFIED
Subject Keywords:Brown dwarfs ; Light curves ; Exoplanet atmospheres
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Brown dwarfs (185); Light curves (918); Exoplanet atmospheres (487)
Record Number:CaltechAUTHORS:20191003-113815666
Persistent URL:
Official Citation:Paulo A. Miles-Páez et al 2019 ApJ 883 181
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99053
Deposited By: George Porter
Deposited On:03 Oct 2019 22:35
Last Modified:16 Nov 2021 17:43

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