JWST-TST DREAMS: Non-Uniform Dayside Emission for WASP-17b from MIRI/LRS

Abstract

We present the first spectroscopic characterisation of the dayside atmosphere of WASP-17b in the mid-infrared using a single JWST MIRI/LRS eclipse observation. From forward-model fits to the 5-12 $\mu$m emission spectrum, we tightly constrain the heat redistribution factor of WASP-17b to be 0.92$\pm$0.02 at the pressures probed by this data, indicative of inefficient global heat redistribution. We also marginally detect a supersolar abundance of water, consistent with previous findings for WASP-17b, but note our weak constraints on this parameter. These results reflect the thermodynamically rich but chemically poor information content of MIRI/LRS emission data for high-temperature hot Jupiters. Using the eclipse mapping method, which utilises the signals that the spatial emission profile of an exoplanet imprints on the eclipse light curve during ingress/egress due to its partial occultation by the host star, we also construct the first eclipse map of WASP-17b, allowing us to diagnose its multidimensional atmospheric dynamics for the first time. We find a day-night temperature contrast of order 1000 K at the pressures probed by this data, consistent with our derived heat redistribution factor, along with an eastward longitudinal hotspot offset of $18.7_{-3.8}^{+11.1°}$, indicative of the presence of an equatorial jet induced by day-night thermal forcing being the dominant redistributor of heat from the substellar point. These dynamics are consistent with general circulation model predictions for WASP-17b. This work is part of a series of studies by the JWST Telescope Scientist Team (JWST-TST), in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).

28 pages, 8 figures. Published in The Astronomical Journal

References in corpus (29)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
• Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H
• A statistical test for Nested Sampling algorithms
• Exoplanet Reflected Light Spectroscopy with PICASO
• The Atmospheric Circulation of the Hot Jupiter WASP-43b: Comparing Three-Dimensional Models to Spectrophotometric Data
• A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve
• Eureka!: An End-to-End Pipeline for JWST Time-Series Observations
• A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
• On Correlated-noise Analyses Applied To Exoplanet Light Curves
• PICASO 3.0: A One-Dimensional Climate Model for Giant Planets and Brown Dwarfs
• Magnetic Effects in Hot Jupiter Atmospheres
• POSEIDON: A Multidimensional Atmospheric Retrieval Code for Exoplanet Spectra
• Evidence of Three Mechanisms Explaining the Radius Anomaly of Hot Jupiters
• EXOPLINES: Molecular Absorption Cross-Section Database for Brown Dwarf and Giant Exoplanet Atmospheres
• GJ 367b is a dark, hot, airless sub-Earth
• Temporal Variability in Hot Jupiter Atmospheres
• Potassium detection in the clear atmosphere of a hot-Jupiter: FORS2 transmission spectroscopy of WASP-17b
• A New Sedimentation Model for Greater Cloud Diversity in Giant Exoplanets and Brown Dwarfs
• A Comprehensive Analysis of WASP-17b's Transmission Spectrum from Space-Based Observations
• The Brighter-Fatter Effect in the JWST MIRI Si:As IBC detectors I. Observations, impact on science, and modelling
• JWST-TST Proper Motions: I. High-Precision NIRISS Calibration and Large Magellanic Cloud Kinematics
• Multiple Clues for Dayside Aerosols and Temperature Gradients in WASP-69 b from a Panchromatic JWST Emission Spectrum
• How Does Thermal Scattering Shape the Infrared Spectra of Cloudy Exoplanets? A Theoretical Framework and Consequences for Atmospheric Retrievals in the JWST era
• ThERESA: Three-Dimensional Eclipse Mapping with Application to Synthetic JWST Data
• Temperature Structures Associated with Different Components of the Atmospheric Circulation on Tidally Locked Exoplanets
• Non-Axisymmetric Flows on Hot Jupiters with Oblique Magnetic Fields

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