Article (Scientific journals)
Weather on Other Worlds. VI. Optical Spectrophotometry of Luhman 16B Reveals Large-amplitude Variations in the Alkali Lines
Heinze, A. N.; Metchev, Stanimir; Kurtev, Radostin et al.
2021In Astrophysical Journal, 920, p. 108
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Keywords :
Brown dwarfs; Atmospheric clouds; Exoplanet atmospheric variability; Variable stars; Spectrophotometry; Time series analysis; 185; 2180; 2020; 1761; 1556; 1916; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] Using a novel wide-slit, multiobject approach with the GMOS spectrograph on the 8 m Gemini South telescope, we have obtained precise time-series spectrophotometry of the binary brown dwarf Luhman 16 at optical wavelengths over two full nights. The B component of this binary system is known to be variable in the red optical and near-infrared with a period of 5 hr and an amplitude of 5%-20%. Our observations probe its spectrally resolved variability in the 6000-10000 Å range. At wavelengths affected by the extremely strong, broadened spectral lines of the neutral alkali metals (the potassium doublet centered near 7682 Å and the sodium doublet at 5893 Å), we see photometric variations that differ strikingly from those of the 8000-10000 Å "red continuum" that dominates our detected flux. On UT 2014 February 24, these variations are anticorrelated with the red continuum, while on February 25 they have a large relative phase shift. The extent to which the wavelength-dependent photometric behavior diverges from that of the red continuum appears to correlate with the strength of the alkali absorption. We consider but ultimately reject models in which our observations are explained by lightning or auroral activity. A more likely cause is cloud-correlated, altitude-dependent variations in the gas-phase abundances of sodium and potassium, which are in chemical equilibrium with their chlorides in brown dwarf atmospheres. Clouds could influence these chemical equilibria by changing the atmospheric temperature profile and/or through cloud particles acting as chemical catalysts.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Heinze, A. N.;  Institute for Astronomy, University of Hawaii, 2680 Woodlawn, Honolulu, HI 96822, USA
Metchev, Stanimir;  Department of Physics and Astronomy, The University of Western Ontario, 1151 Richmond St, London, ON N6A 3K7, Canada ; Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA
Kurtev, Radostin;  Departamento de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso, Av. Gran Bretana 1111, Casilla 5030, Valparaiso, Chile ; Millennium Institute of Astrophysics, Nuncio Monsenor Sotero Sanz 100, Of. 104, Providencia, Santiago, Chile
Gillon, Michaël  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Language :
English
Title :
Weather on Other Worlds. VI. Optical Spectrophotometry of Luhman 16B Reveals Large-amplitude Variations in the Alkali Lines
Publication date :
01 October 2021
Journal title :
Astrophysical Journal
ISSN :
0004-637X
eISSN :
1538-4357
Publisher :
University of Chicago Press, United States - Illinois
Volume :
920
Pages :
108
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 13 December 2021

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