Atmospheres, Climate, Weather

Re-analysis of 10 Hot-Jupiter Atmospheres With Disequilibrium Chemistry Retrieval

By Keith Cowing

Status Report

astro-ph.EP

June 20, 2025

Filed under astro-ph.EP, atmosphere, disequilibrium chemistry, exoplanet, FRECKLL, hot jupiter, Hubble, JWST, photodissociation

Re-analysis of 10 Hot-Jupiter Atmospheres With Disequilibrium Chemistry Retrieval — Detailed retrieval results for WASP-43 b: Upper row presents (from left to right) the fitting spectra for each retrieval configuration tested through this population study, the retrieved temperature profile, as well as the chemical structure of the planet (only for the “FRECKLL-only” retrieval. The lower row presents the posterior for each test, as normalised distribution. Equivalent figures for the rest of the population sample is available in Appendix C for eclipse retrieval results and Appendix D for transit retrieval results. — astro-ph.EP

Constraining the chemical structure of exoplanetary atmospheres is pivotal for interpreting spectroscopic data and understanding planetary evolution.

Traditional retrieval methods often assume thermochemical equilibrium or free profiles, which may fail to capture disequilibrium processes like photodissociation and vertical mixing. This study leverages the TauREx 3.1 retrieval framework coupled with FRECKLL, a disequilibrium chemistry model, to address these challenges.

The study aims to (1) assess the impact of disequilibrium chemistry on constraining metallicity and C/O ratios; (2) evaluate the role of refractory species (TiO and VO) in spectral retrievals; (3) explore consistency between transit and eclipse observations for temperature and chemical profiles; and (4) determine the effects of retrieval priors and data reduction methods. Ten hot-Jupiter atmospheres were reanalyzed using Hubble Space Telescope (HST) WFC3 data in eclipse and transit.

The TauREx-FRECKLL model incorporated disequilibrium chemistry calculations with a Bayesian framework to infer atmospheric properties. The disequilibrium approach significantly altered retrieved metallicity and C/O ratios compared to equilibrium models, impacting planet formation insights. Retrievals reconciled transit and eclipse temperature profiles in deeper atmospheric layers but not in upper layers.

Results were highly dependent on spectral resolution and retrieval priors, emphasizing limitations of HST data and the need for broader spectral coverage from instruments like JWST. This study demonstrates the feasibility and importance of incorporating disequilibrium chemistry in atmospheric retrievals, highlighting its potential for advancing our understanding of exoplanetary atmospheres with next-generation telescopes.

Deborah Bardet, Quentin Changeat, Olivia Venot, Emilie Panek

Comments: 24 pages, 22 figures, accepted for publication in Astronomy and Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2506.12806 [astro-ph.EP] (or arXiv:2506.12806v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.12806
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Submission history
From: Deborah Bardet
[v1] Sun, 15 Jun 2025 10:43:21 UTC (23,926 KB)
https://arxiv.org/abs/2506.12806
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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