High-resolution, differential, near-infrared transmission spectroscopy of GJ 1214b

I. J M Crossfield, Travis S Barman, Brad M S Hansen

Research output: Contribution to journalArticle

68 Citations (Scopus)

Abstract

The nearby star GJ 1214 hosts a planet intermediate in radius and mass between Earth and Neptune, resulting in some uncertainty as to its nature. We have observed this planet, GJ 1214b, during transit with the high-resolution, near-infrared NIRSPEC spectrograph on the Keck II telescope, in order to characterize the planet's atmosphere. By cross-correlating the spectral changes through transit with a suite of theoretical atmosphere models, we search for variations associated with absorption in the planet atmosphere. Our observations are sufficient to rule out tested model atmospheres with wavelength-dependent transit depth variations ≳ 5 × 10-4 over the wavelength range 2.1-2.4 μm. Our sensitivity is limited by variable slit loss and telluric transmission effects. We find no positive signatures but successfully rule out a number of plausible atmospheric models, including the default assumption of a gaseous, H-dominated atmosphere in chemical equilibrium. Such an atmosphere can be made consistent if the absorption due to methane is reduced. Clouds can also render such an atmosphere consistent with our observations, but only if they lie higher in the atmosphere than indicated by recent optical and infrared measurements. When taken in concert with other observational constraints, our results support a model in which the atmosphere of GJ1214b contains significant H and He, but where CH4 is depleted. If this depletion is the result of photochemical processes, it may also produce a haze that suppresses spectral features in the optical.

Original languageEnglish (US)
Article number132
JournalAstrophysical Journal
Volume736
Issue number2
DOIs
StatePublished - Aug 1 2011
Externally publishedYes

Fingerprint

near infrared
spectroscopy
atmospheres
atmosphere
high resolution
planets
planet
transit
wavelength
Neptune (planet)
atmospheric models
haze
Neptune
optical measurement
wavelengths
spectrographs
slits
chemical equilibrium
depletion
methane

Keywords

  • infrared: stars
  • planets and satellites: individual (GJ 1214b)
  • stars: individual (GJ 1214)
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

High-resolution, differential, near-infrared transmission spectroscopy of GJ 1214b. / Crossfield, I. J M; Barman, Travis S; Hansen, Brad M S.

In: Astrophysical Journal, Vol. 736, No. 2, 132, 01.08.2011.

Research output: Contribution to journalArticle

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