Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres Over a Range of Metallicities and Temperatures

Freedman, Richard; Lustig‐Yaeger, Jacob; Fortney, Jonathan J.; Lupu, Roxana; Marley, Mark S.; Lodders, K.

doi:10.1088/0067-0049/214/2/25

Cited by 358 publications

(362 citation statements)

References 78 publications

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“…At P ≈ 100 bar and T ≈ 1000 K the fit systematically underestimate the Rosseland mean opacities by ≈ 30−50% (see Fig. 8 of Freedman et al 2014). This underestimation of the Rosseland mean opacity directly translates to an underestimation of the radiative gradient and to the appearance of a spurious deep radiative zone and a bias in our estimate of P R/C .…”

Section: Radiative/convective Modelmentioning

confidence: 82%

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A non-grey analytical model for irradiated atmospheres

Parmentier

Guillot

Fortney

et al. 2015

A&A

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100

114

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Context. The recent discovery and characterization of the diversity of the atmospheres of exoplanets and brown dwarfs calls for the development of fast and accurate analytical models. Aims. We wish to assess the goodness of the different approximations used to solve the radiative transfer problem in irradiated atmospheres analytically, and we aim to provide a useful tool for a fast computation of analytical temperature profiles that remains correct over a wide range of atmospheric characteristics. Methods. We quantify the accuracy of the analytical solution derived in paper I for an irradiated, non-grey atmosphere by comparing it to a state-of-the-art radiative transfer model. Then, using a grid of numerical models, we calibrate the different coefficients of our analytical model for irradiated solar-composition atmospheres of giant exoplanets and brown dwarfs. Results. We show that the so-called Eddington approximation used to solve the angular dependency of the radiation field leads to relative errors of up to ∼5% on the temperature profile. For grey or semi-grey atmospheres (i.e., when the visible and thermal opacities, respectively, can be considered independent of wavelength), we show that the presence of a convective zone has a limited effect on the radiative atmosphere above it and leads to modifications of the radiative temperature profile of approximately ∼2%. However, for realistic non-grey planetary atmospheres, the presence of a convective zone that extends to optical depths smaller than unity can lead to changes in the radiative temperature profile on the order of 20% or more. When the convective zone is located at deeper levels (such as for strongly irradiated hot Jupiters), its effect on the radiative atmosphere is again on the same order (∼2%) as in the semi-grey case. We show that the temperature inversion induced by a strong absorber in the optical, such as TiO or VO is mainly due to non-grey thermal effects reducing the ability of the upper atmosphere to cool down rather than an enhanced absorption of the stellar light as previously thought. Finally, we provide a functional form for the coefficients of our analytical model for solar-composition giant exoplanets and brown dwarfs. This leads to fully analytical pressure-temperature profiles for irradiated atmospheres with a relative accuracy better than 10% for gravities between 2.5 m s −2 and 250 m s −2 and effective temperatures between 100 K and 3000 K. This is a great improvement over the commonly used Eddington boundary condition.

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Section: Radiative/convective Modelmentioning

confidence: 82%

“…This reflects the sensitivity of the deep atmospheric structure to the Rosseland mean opacities calculations. As shown by Freedman et al (2014), a variation of ≈10-50% is common between different calculations of the Rosseland mean opacities.…”

Section: Radiative/convective Modelmentioning

confidence: 88%

A non-grey analytical model for irradiated atmospheres

Parmentier

Guillot

Fortney

et al. 2015

A&A

Self Cite

100

114

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“…Given the temperature-pressure profile of the atmosphere and the elemental abundances parametrized with metallicity, [M/H], and C/O, the model first computes the thermochemical equilibrium molecular mixing ratios (and mean molecular weight) using the publicly available Chemical Equilibrium with Applications code (CEA, McBride & Gordon (1996)) 2 . The thermochemically derived opacity relevant mixing ratio profiles (H 2 O, CH 4 , CO, CO 2 , NH 3 , H 2 S, C 2 H 2 , HCN, TiO, VO, Na, K, FeH, H 2 , He), temperature profile, cloud and haze proprieties, and planet bulk parameters (10 bar radius, stellar radius, planetary gravity) are then fed into a transit transmission spectrum model (Line et al (2013b); Greene et al (2016); Line & Parmentier (2016), using the Freedman et al (2008Freedman et al ( , 2014 opacity database) to compute the wavelength-dependent eclipse depth at the appropriate instrument spectral resolving power. For cloudy simulations, we assume a hard gray cloud top pressure set to be at the 1 mbar pressure level, below which the transmittance is set to zero and use the "Rayleigh Haze" power law parameterization (Lecavelier Des Etangs et al 2008) to describe hazes.…”

Section: Transit Transmission Spectra Models and Their Jacobiansmentioning

confidence: 99%

Information Content Analysis for Selection of Optimal JWST Observing Modes for Transiting Exoplanet Atmospheres

Batalha

Line

2017

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The James Webb Space Telescope (JWST) is nearing its launch date of 2018, and is expected to revolutionize our knowledge of exoplanet atmospheres. In order to specifically identify which observing modes will be most useful for characterizing a diverse range of exoplanetary atmospheres, we use an information content based approach commonly used in the studies of Solar System atmospheres. We develop a system based upon these information content methods to trace the instrumental and atmospheric model phase space in order to identify which observing modes are best suited for particular classes of planets, focusing on transmission spectra. Specifically, the atmospheric parameter space we cover is T=600-1800 K, C/O=0.55-1, [M/H]=1-100×Solar for a R=1.39 R J , M=0.59 M J planet orbiting WASP-62-like star. We also explore the influence of a simplified opaque gray cloud on the information content. We find that obtaining broader wavelength coverage over multiple modes is preferred over higher precision in a single mode given the same amount of observing time. Regardless of the planet temperature and composition, the best modes for constraining terminator temperatures, C/O ratios, and metallicity are NIRISS SOSS+NIRSpec G395. If the target's host star is dim enough such that the NIRSpec prism can be used, then it can be used instead of NIRISS SOSS+NIRSpec G395. Lastly, observations that use more than two modes, should be carefully analyzed because sometimes the addition of a third mode results in no gain of information. In these cases, higher precision in the original two modes is favorable.

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“…When computing the spectra for two TP profiles, we assume the day-side abundances for both, consistent with expectations from horizontal mixing (e.g., Cooper & Showman 2006;Agúndez et al 2014). The opacity database is described in Freedman et al (2014).…”

Section: Modeling Toolsmentioning

confidence: 99%

The Impact of Non-Uniform Thermal Structure on the Interpretation of Exoplanet Emission Spectra

Feng¹,

Line²,

Fortney³

et al. 2016

ApJ

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149

122

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The determination of atmospheric structure and molecular abundances of planetary atmospheres via spectroscopy involves direct comparisons between models and data. While varying in sophistication, most model spectra comparisons fundamentally assume one-dimensional (1D) model physics. However, knowledge from general circulation models and of solar system planets suggests that planetary atmospheres are inherently threedimensional in their structure and composition. We explore the potential biases resulting from standard "1D" assumptions within a Bayesian atmospheric retrieval framework. Specifically, we show how the assumption of a single 1D thermal profile can bias our interpretation of the thermal emission spectrum of a hot Jupiter atmosphere that is composed of two thermal profiles. We retrieve spectra of unresolved model planets as observed with a combination of the Hubble Space Telescope Wide Field Camera 3 (WFC3)+Spitzer Infrared Array Camera (IRAC) as well as the James Webb Space Telescope (JWST) under varying differences in the two thermal profiles. For WFC3+IRAC, there is a significantly biased estimate of CH 4 abundance using a 1D model when the contrast is 80%. For JWST, two thermal profiles are required to adequately interpret the data and estimate the abundances when contrast is greater than 40%. We also apply this preliminary concept to the recent WFC3+IRAC phase curve data of the hot Jupiter WASP-43b. We see similar behavior as present in our simulated data: while the H O 2 abundance determination is robust, CH 4 is artificially well-constrained to incorrect values under the 1D assumption. Our work demonstrates the need to evaluate model assumptions in order to extract meaningful constraints from atmospheric spectra and motivates exploration of optimal observational setups.

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Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres Over a Range of Metallicities and Temperatures

Cited by 358 publications

References 78 publications

A non-grey analytical model for irradiated atmospheres

A non-grey analytical model for irradiated atmospheres

Information Content Analysis for Selection of Optimal JWST Observing Modes for Transiting Exoplanet Atmospheres

The Impact of Non-Uniform Thermal Structure on the Interpretation of Exoplanet Emission Spectra

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