A TEMPERATURE AND ABUNDANCE RETRIEVAL METHOD FOR EXOPLANET ATMOSPHERES

By N. Madhusudhan, Sara Seager. 2009

397 citations recorded by the source corpus.

We present a new method to retrieve molecular abundances and temperature profiles from exoplanet atmosphere photometry and spectroscopy. We run millions of one-dimensional (1D) atmosphere models in order to cover the large range of allowed parameter space. In order to run such a large number of models, we have developed a parametric pressure–temperature (P–T) profile coupled with line-by-line radiative transfer, hydrostatic equilibrium, and energy balance, along with prescriptions for non-equilibrium molecular composition and energy redistribution. The major difference from traditional 1D radiative transfer models is the parametric P–T profile, which essentially means adopting energy balance only at the top of the atmosphere and not in each layer. We see the parametric P–T model as a parallel approach to the traditional exoplanet atmosphere models that rely on several free parameters to encompass unknown absorbers and energy redistribution. The parametric P–T profile captures the basic physical features of temperature structures in planetary atmospheres (including temperature inversions), and fits a wide range of published P–T profiles, including those of solar system planets. We apply our temperature and abundance retrieval method to the atmospheres of two transiting exoplanets, HD 189733b and HD 209458b, which have the best Spitzer and Hubble Space Telescope data available. For HD 189733b, we find efficient day–night redistribution of energy in the atmosphere, and molecular abundance constraints confirming the presence of H2O, CO, CH4, and CO2. For HD 209458b, we confirm and constrain the dayside thermal inversion in an average 1D temperature profile. We also report independent detections of H2O, CO, CH4, and CO2 on the dayside of HD 209458b, based on six-channel Spitzer photometry. We report constraints for HD 189733b due to individual data sets separately; a few key observations are variable in different data sets at similar wavelengths. Moreover, a noticeably strong CO2 absorption in one data set is significantly weaker in another. We must, therefore, acknowledge the strong possibility that the atmosphere is variable, both in its energy redistribution state and in the chemical abundances.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fdb21991cfcc80b57892b9030b13500d6ebd7556

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In Astronomy and Astrophysics

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

In Instrumentation

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

Citations in the corpus

• WATER VAPOR IN THE SPECTRUM OF THE EXTRASOLAR PLANET HD 189733b. I. THE TRANSIT (2014, methodology): “0.1 bar), the temperature profile has typical isothermal temperatureof ∼700 K, slightly cooler than prior P-T curves used to model NICMOS transmission spectra of HD 189733b’s terminator and its day-side emission spectrum fromSpitzer(c.f. Figures 5 and 8 of Madhusudhan & Seager 2009).”
• A chemical model for the atmosphere of hot Jupiters (2012, methodology): “These observations can be used to constrain the thermal profile (Swain et al. 2009a; Madhusudhan & Seager 2009) and to detect the spectral signature of atmospheric compounds (Charbonneau et al. 2002; Tinetti et al. 2007; Swain et al. 2008b; Grillmair et al. 2008; Langland-Shula et al. 2009; Swain…”
• Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy (2011, background): “Finally, a decreasing temperature with altitude between 0.01-1.0 bar suggested the presnc of a troposphere (S09; Madhusudhan & Seager 2009, hereafter MS09).”
• On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets (2014, background): “Madhusudhan & Seager (2009), by comparing observations of HD 189733b and HD 209458b to a multidimensional grid of models, reported constraints on the atmospheric thermal structure and concentrations of several key gases for these worlds.”
• A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA (2010, background): “…chemistry and pressure-temperature profiles are allowed to vary find that this planet is best-described by a model with a temperature inversion at altitude (Madhusudhan & Seager 2009; Swain et al. 2009b), consistent with the conclusions of more highly-constrained models (e.g. Burrows et al. 2007).”
• Transits and Occultations (2010, background): “Recent work by Madhusudhan & Seager (2009) addresses this problem.”
• A DETECTION OF WATER IN THE TRANSMISSION SPECTRUM OF THE HOT JUPITER WASP-12b AND IMPLICATIONS FOR ITS ATMOSPHERIC COMPOSITION (2015, methodology): “The first is the widely adopted approach of retrieving molecular abundances without any constraints from chemistry (e.g. Madhusudhan & Seager 2009).”
• 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.”
• A SYSTEMATIC RETRIEVAL ANALYSIS OF SECONDARY ECLIPSE SPECTRA. I. A COMPARISON OF ATMOSPHERIC RETRIEVAL TECHNIQUES (2013, methodology): “The second is a parameterized temperature profile approach similar to the approach used in Madhusudhan & Seager 2009 and Line et al. 2012.”
• SPECTROSCOPIC EVIDENCE FOR A TEMPERATURE INVERSION IN THE DAYSIDE ATMOSPHERE OF HOT JUPITER WASP-33b (2015, methodology): “The model computes line-by-line radiative transfer for a plane-parallel atmosphere with the assumptions of hydrostatic equilibrium and global energy balance, as described in Madhusudhan & Seager (2009).”
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, background): “There also exists the temperature parametrization suggested by Madhusudhan & Seager (2009), which allows to parametrize temperature structures with or without inversions, and with or without a deep isothermal layer, as commonly expected for hot Jupiter planets.”
• NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY (2016, methodology): “The chemical retrieval-on-retrieval approach straddles the line between the classic “fully data driven” (Madhusudhan & Seager 2009; Lee et al. 2012; Line et al. 2012; Barstow et al. 2012; Benneke & Seager 2013; Line et al. 2014) and “a priori imposition of physical processes” (Knutson et al. 2014,…”
• On the radiative equilibrium of irradiated planetary atmospheres (2010, background): “…of primary and secondary transits at different Send offprint requests to: T. Guillot wavelengths have even brought the possibility to test thesemodels and led to the identification of key molecular species (e.g. Tinetti et al. 2007; Barman 2008; Madhusudhan & Seager 2009; Swain et al. 2010).”
• 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).”
• H2O abundances and cloud properties in ten hot giant exoplanets (2018, methodology): “T profile is able to fit disparate planetary atmosphere structures, mimicking atmospheric conditions of solar system planets as well as exoplanetary atmosphere models in the literature (Madhusudhan & Seager 2009).”