Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy

By Jae-Min Lee, L. Fletcher, P. Irwin. 2011

154 citations recorded by the source corpus.

Recent spectroscopic observations of transiting hot Jupit ers have permitted the derivation of the thermal structure and molecular abundances of H2O, CO2, CO, and CH4 in these extreme atmospheres. Here, for the first time, we apply the tech nique of optimal estimation to determine the thermal structure and composition of an exoplanet by solving the inverse problem. The development of a suite of radiative transfer and retrieval tools for exoplanet atmospheres is described, building upon a retrieval algori thm which is extensively used in the study of our own solar system. First, we discuss the plausibility of detection of different molecules in the dayside atmosphere of HD 189733b and the best-fitting spectrum retrieved from all publicly available sets of secondary eclipse obser vations between 1.45 and 24 µm. Additionally, we use contribution functions to assess the vertical sensitivity of the emission spectrum to temperatures and molecular composition. Over the altitudes probed by the contribution functions, the retrieved thermal structure show s an isothermal upper atmosphere overlying a deeper adiabatic layer (temperature decreasing with altitude), which is consistent with previously-reported dynamical and observational results. The formal uncertainties on retrieved parameters are estimated conservatively using an analysis of the cross-correlation functions and the degeneracy between different atmospheric properties. The formal solution of the inverse problem suggests that the uncertainties on retr ieved parameters are larger than suggested in previous studies, and that the presence of CO and CH4 is only marginally supported by the available data. Nevertheless, by including as broad a wavelength range as possible in the retrieval, we demonstrate that available spectra of HD 189733b can constrain a family of potential solutions for the atmospheric structure.

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

View Paper: https://www.semanticscholar.org/paper/12ecda01e36c15be3efcb0226bc59df583f5d5e9

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In Astronomy and Astrophysics

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

In Instrumentation

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

In Statistical and Nonlinear Physics

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

Citations in the corpus

• Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b (2013, methodology): “Numerous secondary eclipse measurements (e.g. Deming et al. 2006; Grillmair et al. 2008; Charbonneau et al. 2008; Swain et al. 2009) have placed constraints on the day-side temperature structure and trace gas abundances (e.g. Madhusudhan & Seager 2009; Line et al. 2012; Lee et al. 2012).”
• 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).”
• CHARACTERIZING TRANSITING EXOPLANET ATMOSPHERES WITH JWST (2015, background): “…limits) of molecules such CO, CO2, and CH4 in addition to H2O in ∼ 10 exoplanet atmospheres (e.g., Madhusudhan & Seager 2009; Madhusudhan et al. 2011; Lee et al. 2012; Line et al. 2012; Barstow et al. 2013a,b; Benneke & Seager 2012, 2013; Line et al. 2013a, 2014a; Benneke 2015; Waldmann et al.…”
• On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets (2014, methodology): “More sophisticated retrieval methods have also been applied to observations of hot Jupiters, including optimal estimation techniques (Lee et al. 2012; Line et al. 2012) and Markov chain Monte Carlo methods (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): “Lee et al. (2012) considered all available data sets.”
• HD 209458b in new light: evidence of nitrogen chemistry, patchy clouds and sub-solar water (2017, methodology): “Early retrievals used grid-based parameter space exploration (Madhusudhan & Seager 2009) or optimal estimation techniques (Lee et al. 2012; Line et al. 2012; Barstow et al. 2013) that do not allow for full marginalisation of the posterior.”
• Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST) (2014, unknown): “2b; Lee et al. 2012).”
• A CONSISTENT RETRIEVAL ANALYSIS OF 10 HOT JUPITERS OBSERVED IN TRANSMISSION (2016, methodology): “For this work, we use the NEMESIS radiative transfer and retrieval code, initially developed for solar system planets (Irwin et al. 2008) and subsequently used in several analyses of transiting exoplanet atmospheres (Lee et al. 2012; Barstow et al. 2013b, 2014; Lee et al. 2014).”
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, background): “…in every layer of the discretized atmosphere independently, which is an approach commonly followed in the planetary science community (e.g., Rodgers 2000; Irwin et al. 2008), and which has also been applied to cloud-free brown dwarfs (Line et al. 2014a) and exoplanets (e.g., Lee et al. 2012).”
• NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY (2016, methodology): “We integrate out vertical profile information by column averaging the thermochemically derived mixing ratio profiles over the infrared photosphere (3bars -1 mbar), as low resolution spectra are largely insensitive to vertical profile information (e.g., Lee et al. 2012; Barstow et al. 2013).”
• A SYSTEMATIC RETRIEVAL ANALYSIS OF SECONDARY ECLIPSE SPECTRA. I. A COMPARISON OF ATMOSPHERIC RETRIEVAL TECHNIQUES (2013, methodology): “This is the approach used in Lee et al. 2012.”
• The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations (2012, background): “By necessity, information is often inferred for exoplanets by fitting suites of model spectra in a Bayesian fashion to a few Spitzer passbands, sometimes complemented by a few ground-based measurements at shorter wavelength (Madhusudhan et al. 2011; Lee et al. 2012).”
• 3D mixing in hot Jupiters atmospheres. I. Application to the day/night cold trap in HD 209458b (2013, methodology): “Therefore, interpretation of the data is usually done using one dimensional atmospheric models, assuming an homogenous atmosphere, both in term of temperature structure and composition (e.g., Madhusudhan & Seager 2009; Lee et al. 2012; Benneke & Seager 2012, among others).”