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

Abstract

We use the Wide Field Camera 3 on the {\sl Hubble Space Telescope} to spectrophotometrically monitor the young L7.5 companion HD~203030B. Our time series reveal photometric variability at 1.27\,$\mu$m and 1.39\,$\mu$m on time scales compatible with rotation. We find a rotation period of $7.5_{-0.5}^{+0.6}$ h: comparable to those observed in other brown dwarfs and planetary-mass companions younger than 300 Myr. We measure variability amplitudes of $1.1\pm 0.3\%$ (1.27\,$\mu$m) and $1.7\pm 0.4\%$ (1.39\,$\mu$m), and a phase lag of 56${}^{\circ }\pm$28${}^{\circ }$ 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 vs.\ old T dwarfs.

arXiv commentAccepted for publication in The Astrophysical Journal

References in corpus (46)

• The Gaia mission
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Precipitating Condensation Clouds in Substellar Atmospheres
• The Theory of Brown Dwarfs and Extrasolar Giant Planets
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• A Giant Planet Candidate near a Young Brown Dwarf
• The Flat Transmission Spectrum of the Super-Earth GJ1214b from Wide Field Camera 3 on the Hubble Space Telescope
• Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b
• On the age of the $\beta$ Pictoris moving group
• Masses, Radii, and Cloud Properties of the HR 8799 Planets
• Weather on Other Worlds. II. Survey Results: Spots Are Ubiquitous on L and T Dwarfs
• Population Properties of Brown Dwarf Analogs to Exoplanets
• Photometric Variability of the T2.5 Brown Dwarf SIMP J013656.5+093347; Evidence for Evolving Weather Patterns
• A companion to AB Pic at the planet/brown dwarf boundary
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• Discovery of Two T Dwarf Companions with the Spitzer Space Telescope
• HST Spectral Mapping of L/T Transition Brown Dwarfs Reveals Cloud Thickness Variations
• The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• HD 203030B: an Unusually Cool Young Sub-Stellar Companion near the L/T Transition
• The Slitless Spectroscopy Data Extraction Software aXe
• Brown Dwarf Photospheres are Patchy: A Hubble Space Telescope Near-infrared Spectroscopic Survey Finds Frequent Low-level Variability
• The Young Planet-mass Object 2M1207b: a cool, cloudy, and methane-poor atmosphere
• Planets Around Low-Mass Stars (PALMS). III. A Young Dusty L Dwarf Companion at the Deuterium-Burning Limit
• $ExtrasolarStorms$: Pressure-dependent Changes In Light Curve Phase In Brown Dwarfs From Simultaneous $Hubble$ and $Spitzer$ Observations
• A Physical Model-based Correction for Charge Traps in the Hubble Space Telescope's Wide Field Camera 3 Near-IR Detector and Applications to Transiting Exoplanets and Brown Dwarfs
• Discovery of Rotational Modulations in the Planetary-Mass Companion 2M1207b: Intermediate Rotation Period and Heterogeneous Clouds in a Low Gravity Atmosphere
• A Kine-Chemical Investigation of the AB Dor Moving Group "Stream"
• Discovery of an Unusually Red L-type Brown Dwarf
• Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition
• High-Cadence, High-Contrast Imaging for Exoplanet Mapping: Observations of the HR 8799 Planets with VLT/SPHERE Satellite Spot-Corrected Relative Photometry
• Temperature Fluctuations as a Source of Brown Dwarf Variability
• Simultaneous, Multi-Wavelength Variability Characterization of the Free-Floating Planetary Mass Object PSO J318.5-22
• Cloud structure of the nearest brown dwarfs: Spectroscopic variability of Luhman 16AB from the Hubble Space Telescope
• Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf
• HST Rotational Spectral Mapping of Two L-Type Brown Dwarfs: Variability In and Out of Water Bands Indicates High-Altitude Haze Layers
• Variability of the Lowest Mass Objects in the AB Doradus Moving Group
• Cloud Atlas: Rotational Spectral Modulations and potential Sulfide Clouds in the Planetary-mass, Late T-type Companion Ross 458C
• Cloud Atlas: Discovery of Rotational Spectral Modulations in a Low-mass, L-type Brown Dwarf Companion to a Star
• Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B
• Cloud Atlas: High-Contrast Time-Resolved Observations of Planetary-Mass Companions
• Rotation Periods of Young Brown Dwarfs: K2 Survey in Upper Scorpius
• Kepler Monitoring of an L Dwarf II. Clouds with Multiyear Lifetimes
• The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass
• Spitzer Light Curves of the Young, Planetary-Mass TW Hya Members 2MASS J11193254-1137466AB and WISEA J114724.10-204021.3

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• Let the Great World Spin: Revealing the Stormy, Turbulent Nature of Young Giant Exoplanet Analogs with the Spitzer Space Telescope
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• A Unified Spectroscopic and Photometric Model to Infer Surface Inhomogeneity: Application to Luhman 16B
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