A systematic retrieval analysis of secondary eclipse spectra. I. A comparison of atmospheric retrieval techniques

Michael Line, Aaron S. Wolf, Xi Zhang, Heather Knutson, Joshua A. Kammer, Elias Ellison, Pieter Deroo, Dave Crisp, Yuk L. Yung

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

Exoplanet atmosphere spectroscopy enables us to improve our understanding of exoplanets just as remote sensing in our own solar system has increased our understanding of the solar system bodies. The challenge is to quantitatively determine the range of temperatures and molecular abundances allowed by the data, which is often difficult given the low information content of most exoplanet spectra that commonly leads to degeneracies in the interpretation. A variety of spectral retrieval approaches have been applied to exoplanet spectra, but no previous investigations have sought to compare these approaches. We compare three different retrieval methods: optimal estimation, differential evolution Markov chain Monte Carlo, and bootstrap Monte Carlo on a synthetic water-dominated hot Jupiter. We discuss expectations of uncertainties in abundances and temperatures given current and potential future observations. In general, we find that the three approaches agree for high spectral resolution, high signal-to-noise data expected to come from potential future spaceborne missions, but disagree for low-resolution, low signal-to-noise spectra representative of current observations. We also compare the results from a parameterized temperature profile versus a full classical Level-by-Level approach and discriminate in which situations each of these approaches is applicable. Furthermore, we discuss the implications of our models for the inferred C-to-O ratios of exoplanetary atmospheres. Specifically, we show that in the observational limit of a few photometric points, the retrieved C/O is biased toward values near solar and near one simply due to the assumption of uninformative priors.

Original languageEnglish (US)
Article number137
JournalAstrophysical Journal
Volume775
Issue number2
DOIs
StatePublished - Oct 1 2013
Externally publishedYes

Fingerprint

eclipses
extrasolar planets
retrieval
solar system
atmospheres
Markov chains
noise spectra
Jupiter (planet)
spectral resolution
temperature profiles
atmosphere
remote sensing
Markov chain
estimation method
temperature profile
Jupiter
temperature
spectroscopy
comparison
analysis

Keywords

  • methods: data analysis
  • methods: statistical
  • planets and satellites: atmospheres
  • radiative transfer

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics
  • Nuclear and High Energy Physics

Cite this

A systematic retrieval analysis of secondary eclipse spectra. I. A comparison of atmospheric retrieval techniques. / Line, Michael; Wolf, Aaron S.; Zhang, Xi; Knutson, Heather; Kammer, Joshua A.; Ellison, Elias; Deroo, Pieter; Crisp, Dave; Yung, Yuk L.

In: Astrophysical Journal, Vol. 775, No. 2, 137, 01.10.2013.

Research output: Contribution to journalArticle

Line, Michael ; Wolf, Aaron S. ; Zhang, Xi ; Knutson, Heather ; Kammer, Joshua A. ; Ellison, Elias ; Deroo, Pieter ; Crisp, Dave ; Yung, Yuk L. / A systematic retrieval analysis of secondary eclipse spectra. I. A comparison of atmospheric retrieval techniques. In: Astrophysical Journal. 2013 ; Vol. 775, No. 2.
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