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
AuthorMiles-Páez, Paulo A.
Lew, Ben W. P.
Burgasser, Adam J.
Bedin, Luigi R.
Lowrance, Patrick J.
Marley, Mark S.
AffiliationUniv Arizona, Dept Astron, Steward Observ
Univ Arizona, Lunar & Planetary Lab, Dept Planetary Sci
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationPaulo A. Miles-Páez et al 2019 ApJ 883 181
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe 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 mu m 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 mu m) and 1.7% +/- 0.4% (1.39 mu m), and a phase lag of 56 degrees +/- 28 degrees 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 mu m 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.
VersionFinal published version
SponsorsNASANational Aeronautics & Space Administration (NASA) [NAS 5-26555, GO 14241]; Natural Sciences and Engineering Research Council of CanadaNatural Sciences and Engineering Research Council of Canada [RGPIN-04396-2014]; Canada Research Chairs ProgramCanada Research Chairs