JWST MIRI/LRS data combined with archival observations detect magnesium silicate clouds (likely Mg2SiO4) in HD 209458b at 1-10 mbar with ~0.1 micron particles using a new rule-based data reduction approach.
Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
5 Pith papers cite this work. Polarity classification is still indexing.
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abstract
The Neptune-mass GJ 436b is one of the most-studied transiting exoplanets with repeated measurements of both its thermal emission and transmission spectra. We build on previous studies to answer outstanding questions about this planet, including its potentially high metallicity and tidal heating of its interior. We present new observations of GJ 436b's thermal emission at 3.6 and 4.5 micron, which reduce uncertainties in estimates of GJ 436b's flux at those wavelengths and demonstrate consistency between Spitzer observations spanning more than 7 years. We analyze the Spitzer thermal emission photometry and Hubble WFC3 transmission spectrum in tandem. We use a powerful dual-pronged modeling approach, comparing these data to both self-consistent and retrieval models. We vary the metallicity, intrinsic luminosity from tidal heating, disequilibrium chemistry, and heat redistribution. We also study the effect of clouds and photochemical hazes on the spectra, but do not find strong evidence for either. The self-consistent and retrieval modeling combine to suggest that GJ 436b has a high atmospheric metallicity, with best fits at or above several hundred times solar metallicity, tidal heating warming its interior with best-fit intrinsic effective effective temperatures around 300--350 K, and disequilibrium chemistry. High metal-enrichments (>600x solar) can only occur from the accretion of rocky, rather than icy, material. Assuming Tint~300--350 K, we find that Q'~2x10^5--10^6, larger than Neptune's Q', and implying a long tidal circularization timescale for the planet's orbit. We suggest that Neptune-mass planets may be a more diverse class than previously imagined, with metal-enhancements potentially spanning several orders of magnitude, to perhaps over 1000x solar metallicity. High fidelity observations with instruments like JWST will be critical for characterizing this diversity.
fields
astro-ph.EP 5years
2026 5representative citing papers
Horizontal quenching at wind speeds ≳500 m/s, plus carbon-sulfur chemistry, explains the MIRI non-detection of night-side methane on WASP-43 b without requiring high metallicity.
A matrix-based extension of Papaloizou (2015) gives the tidal separation timescale T for N-planet chains and converts observed offsets into effective Q' bounds, with special sensitivity to the second and outermost planet masses.
A quench-pressure parameterisation with two free parameters recovers unbiased C/O and [M/H] from synthetic JWST spectra with vertical mixing, and tentatively detects quenching and photochemical H2S depletion in HD 189733b NIRCam data.
citing papers explorer
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Magnesium Silicate Clouds in the Atmosphere of HD 209458b from a Rule-Based Tree-Structured Data Reduction
JWST MIRI/LRS data combined with archival observations detect magnesium silicate clouds (likely Mg2SiO4) in HD 209458b at 1-10 mbar with ~0.1 micron particles using a new rule-based data reduction approach.
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Phase-dependent chemistry of WASP-43 b revealed with a suite of one-, two-, and three-dimensional models
Horizontal quenching at wind speeds ≳500 m/s, plus carbon-sulfur chemistry, explains the MIRI non-detection of night-side methane on WASP-43 b without requiring high metallicity.
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How to measure tidal dissipation in long resonant chains
A matrix-based extension of Papaloizou (2015) gives the tidal separation timescale T for N-planet chains and converts observed offsets into effective Q' bounds, with special sensitivity to the second and outermost planet masses.
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A parameterised approach to disequilibrium retrievals in the JWST era: Application to NIRCam observations of HD 189733b
A quench-pressure parameterisation with two free parameters recovers unbiased C/O and [M/H] from synthetic JWST spectra with vertical mixing, and tentatively detects quenching and photochemical H2S depletion in HD 189733b NIRCam data.
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