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

By M. Line, A. Wolf, Xi Zhang, H. Knutson, J. Kammer, E. Ellison, P. Deroo, David Crisp, Yuk L. Yung. 2013

236 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/e48759dac6f794affece04131cc0652433666dbe

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In Astronomy and Astrophysics

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Line
5. M. Marley
6. J. D'esert
7. V. Parmentier
8. H. Knutson

In Instrumentation

1. N. Madhusudhan
2. Jon Fortney
3. A. Showman
4. M. Line
5. M. Marley
6. H. Knutson
7. V. Parmentier
8. J. D'esert

In Statistical and Nonlinear Physics

1. N. Madhusudhan
2. Jon Fortney
3. M. Line
4. V. Parmentier
5. H. Knutson
6. Sara Seager
7. M. Marley
8. A. Showman

Citations in the corpus

• A DETECTION OF WATER IN THE TRANSMISSION SPECTRUM OF THE HOT JUPITER WASP-12b AND IMPLICATIONS FOR ITS ATMOSPHERIC COMPOSITION (2015, methodology): “Modifications to the retrieval code and description of the transmission forward model are provided in Line et al. (2013a); Stevenson et al. (2014d); Kreidberg et al. (2014a); Swain et al. (2014); DiamondLowe et al. (2014).”
• From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context (2018, methodology): “Retrieval models, used to quantify molecular abundances from spectra often neglect both H− opacities and the height dependence of the molecular abundances (e.g., Madhusudhan & Seager 2009; Lee et al. 2012; Line et al. 2013).”
• HD 209458b in new light: evidence of nitrogen chemistry, patchy clouds and sub-solar water (2017, methodology): “Rigorous parameter estimation in a Bayesian framework was enabled by the integration of Markov Chain Monte Carlo (MCMC) algorithms into retrieval codes (e.g. Madhusudhan et al. 2011; Benneke & Seager 2012; Line et al. 2013).”
• A SYSTEMATIC RETRIEVAL ANALYSIS OF SECONDARY ECLIPSE SPECTRA. II. A UNIFORM ANALYSIS OF NINE PLANETS AND THEIR C TO O RATIOS (2013, methodology): “We present results from the DEMC approach in our final abundance catalogue, as this is the more widely accepted, robust approach for current exoplanet data (e.g, Benneke & Seager 2012; Line et al. 2013).”
• TAU-REX I: A NEXT GENERATION RETRIEVAL CODE FOR EXOPLANETARY ATMOSPHERES (2014, background): “Line et al. (2013) provides a recent and comprehensive review of currently existing exoplanetary atmospheric retrieval codes.”
• CHARACTERIZING TRANSITING EXOPLANET ATMOSPHERES WITH JWST (2015, methodology): “The uncertainties in molecular mixing ratios retrieved from JWST emission spectra (even λ ≥ 5 µm) for single observations are too large to obtain a definitive detection of vertical mixing via the method of Line et al. (2013b).”
• A PRECISE WATER ABUNDANCE MEASUREMENT FOR THE HOT JUPITER WASP-43b (2014, methodology): “For the transmission spectrum modeling, we retrieved an effective scale height temperature, a reference pressure at which the fiducial radius is defined, and an opaque gray cloud top pressure, in addition to the molecular abundances (Line et al. 2013a).”
•  ?> -REx. II. RETRIEVAL OF EMISSION SPECTRA (2015, background): “Line et al. (2013) provides a comparison of existing exoplanetary emission spectroscopy retrieval codes. ar X iv :1 50 8.”
• Global Climate and Atmospheric Composition of the Ultra-hot Jupiter WASP-103b from HST and Spitzer Phase Curve Observations (2018, methodology): “Using these opacities and T-P profiles, we calculated thermal emission spectra over the full grid using the CHIMERA retrieval suite (described in Line et al. 2013, 2014).”
• NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY (2016, methodology): “The temperature-pressure (T-P) profile is parameterized (with 5 parameters) using the analytic approximation from Parmentier & Guillot 2014 (see Line et al. 2013 for implementation details).”
• H− Opacity and Water Dissociation in the Dayside Atmosphere of the Very Hot Gas Giant WASP-18b (2018, methodology): “Atmospheric modelling including H− opacities and molecular dissociation We produce a newly developed cloud-free grid of 1D self-consistent radiative-convective-thermochemical equilibrium models to interpret the data (ScCHIMERA, Self-consistent CHIMERA, Line et al. 2013).”
• Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects (2019, unknown): “The exoplanet H2O abundances are from various works: HD 209458b (206, 151), HD 189733b (206, 278), WASP12b (206), WASP-43b (132), WASP-33b (102), TrES-3 (148), GJ 436b (187), HAT-P-26b (277), WASP-39b (206), HR 8799 planets (143), κ And b (262).”
• SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, methodology): “…We derive the planet’s atmospheric composition and thermal structure using the CHIMERA Bayesian retrieval suite, which is described in detail by Line et al. (2013, 2014) and was previously used to interpret WASP-43b’s atmosphere using HST/WFC3 data (Kreidberg et al. 2014; Stevenson et al.…”