Simultaneous detection of water, methane, and carbon monoxide in the atmosphere of Exoplanet hr 8799 b

Travis S Barman, Quinn M. Konopacky, Bruce Macintosh, Christian Marois

Research output: Contribution to journalArticle

59 Citations (Scopus)

Abstract

Absorption lines from water, methane, and carbon monoxide are detected in the atmosphere of exoplanet HR 8799 b. A medium-resolution spectrum presented here shows well-resolved and easily identified spectral features from all three molecules across the K band. The majority of the lines are produced by CO and H<inf>2</inf>O, but several lines clearly belong to CH<inf>4</inf>. Comparisons between these data and atmosphere models covering a range of temperatures and gravities yield log mole fractions of H<inf>2</inf>O between -3.09 and -3.91, CO between -3.30 and -3.72, and CH<inf>4</inf> between -5.06 and -5.85. More precise mole fractions are obtained for each temperature and gravity studied. A reanalysis of H-band data, previously obtained at a similar spectral resolution, results in a nearly identical water abundance as determined from the K-band spectrum. The methane abundance is shown to be sensitive to vertical mixing and indicates an eddy diffusion coefficient in the range of 10<sup>6</sup>-10<sup>8</sup> cm<sup>2</sup> s<sup>-1</sup>, comparable to mixing in the deep troposphere of Jupiter. The model comparisons also indicate a carbon-to-oxygen ratio (C/O) between ∼0.58 and 0.7, encompassing previous estimates for a second planet in the same system, HR 8799 c. Super-stellar C/O could indicate planet formation by core-accretion; however, the range of possible C/O for these planets (and the star) is currently too large to comment strongly on planet formation. More precise values of the bulk properties (e.g., effective temperature and surface gravity) are needed for improved abundance estimates.

Original languageEnglish (US)
Article number61
JournalAstrophysical Journal
Volume804
Issue number1
DOIs
StatePublished - May 1 2015

Fingerprint

extrasolar planets
carbon monoxide
planets
methane
planet
atmospheres
atmosphere
gravity
gravitation
extremely high frequencies
water
turbulent diffusion
temperature
vertical mixing
estimates
troposphere
spectral resolution
Jupiter (planet)
Jupiter
eddy

Keywords

  • brown dwarfs
  • planetary systems
  • stars: atmospheres
  • stars: low-mass

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Simultaneous detection of water, methane, and carbon monoxide in the atmosphere of Exoplanet hr 8799 b. / Barman, Travis S; Konopacky, Quinn M.; Macintosh, Bruce; Marois, Christian.

In: Astrophysical Journal, Vol. 804, No. 1, 61, 01.05.2015.

Research output: Contribution to journalArticle

Barman, Travis S ; Konopacky, Quinn M. ; Macintosh, Bruce ; Marois, Christian. / Simultaneous detection of water, methane, and carbon monoxide in the atmosphere of Exoplanet hr 8799 b. In: Astrophysical Journal. 2015 ; Vol. 804, No. 1.
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