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Strong Near-infrared Spectral Variability of the Young Cloudy L Dwarf Companion VHS J1256–1257 b

Bowler, Brendan P. and Zhou, Yifan and Morley, Caroline V. and Kataria, Tiffany and Bryan, Marta L. and Benneke, Björn and Batygin, Konstantin (2020) Strong Near-infrared Spectral Variability of the Young Cloudy L Dwarf Companion VHS J1256–1257 b. Astrophysical Journal Letters, 893 (2). Art. No. L30. ISSN 2041-8213. doi:10.3847/2041-8213/ab8197.

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Rotationally modulated variability of brown dwarfs and giant planets provides unique information about their surface brightness inhomogeneities, atmospheric circulation, cloud evolution, vertical atmospheric structure, and rotational angular momentum. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared time-series spectroscopic observations of three companions with masses in or near the planetary regime: VHS J125601.92–125723.9 b, GSC 6214–210 B, and ROXs 42 B b. VHS J1256–1257 b exhibits strong total intensity and spectral variability with a brightness difference of 19.3% between 1.1 and 1.7 μm over 8.5 hr and even higher variability at the 24.7% level at 1.27 μm. The light curve of VHS J1256–1257 b continues to rise at the end of the observing sequence so these values represent lower limits on the full variability amplitude at this epoch. This observed variability rivals (and may surpass) the most variable brown dwarf currently known, 2MASS J21392676+0220226. The implied rotation period of VHS J1256–1257 b is ≈21–24 hr assuming sinusoidal modulations, which is unusually long for substellar objects. No significant variability is evident in the light curves of GSC 6214–210 B (<1.2%) and ROXs 42 B b (<15.6%). With a spectral type of L7, an especially red spectrum, and a young age, VHS J1256–1257 b reinforces emerging patterns between high variability amplitude, low surface gravity, and evolutionary phase near the L/T transition.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Bowler, Brendan P.0000-0003-2649-2288
Zhou, Yifan0000-0003-2969-6040
Morley, Caroline V.0000-0002-4404-0456
Kataria, Tiffany0000-0003-3759-9080
Bryan, Marta L.0000-0002-6076-5967
Benneke, Björn0000-0001-5578-1498
Batygin, Konstantin0000-0002-7094-7908
Additional Information:© 2020 The American Astronomical Society. Received 2020 January 27; revised 2020 March 18; accepted 2020 March 19; published 2020 April 17. The authors thank the referee for comments that improved this manuscript, as well as Heather Knutson and Trent Dupuy for helpful discussions. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 15197. B.P.B. acknowledges support from the National Science Foundation grant AST-1909209. Facility: HST (WFC3). -
Group:Astronomy Department
Funding AgencyGrant Number
NASANAS 5-26555
Subject Keywords:Brown dwarfs ; Exoplanet atmospheric variability
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Brown dwarfs (185); Exoplanet atmospheric variability (2020)
Record Number:CaltechAUTHORS:20200417-142604783
Persistent URL:
Official Citation:Brendan P. Bowler et al 2020 ApJL 893 L30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102615
Deposited By: Tony Diaz
Deposited On:17 Apr 2020 21:36
Last Modified:16 Nov 2021 18:13

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