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Title: A SYSTEMATIC RETRIEVAL ANALYSIS OF SECONDARY ECLIPSE SPECTRA. I. A COMPARISON OF ATMOSPHERIC RETRIEVAL TECHNIQUES

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 themore » 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.« less
Authors:
; ; ; ; ;  [1] ;  [2] ; ;  [3]
  1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Flintridge Preparatory School, La CaƱada, CA 91011 (United States)
  3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099 (United States)
Publication Date:
OSTI Identifier:
22270877
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 775; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CARBON; COMPARATIVE EVALUATIONS; DATA ANALYSIS; ECLIPSE; ELEMENT ABUNDANCE; MARKOV PROCESS; MONTE CARLO METHOD; OXYGEN; PLANETARY ATMOSPHERES; PLANETS; POTENTIALS; RADIANT HEAT TRANSFER; REMOTE SENSING; RESOLUTION; SATELLITE ATMOSPHERES; WATER