JWST-TST DREAMS: A Precise Water Abundance for Hot Jupiter WASP-17b from the NIRISS SOSS Transmission Spectrum

Abstract

Water has proven to be ubiquitously detected in near-infrared (NIR) transmission spectroscopy observations of hot Jupiter atmospheres, including WASP-17b. However, previous analyses of WASP-17b's atmosphere based upon Hubble Space Telescope (HST) and Spitzer data could not constrain the water abundance, finding that sub-solar, super-solar and bimodal posterior distributions were all statistically valid. In this work, we observe one transit of the hot Jupiter WASP-17b using JWST's Near Infrared Imager and Slitless Spectrograph Single Object Slitless Spectroscopy (NIRISS SOSS) mode. We analyze our data using three independent data analysis pipelines, finding excellent agreement between results. Our transmission spectrum shows multiple H${}_2$O absorption features and a flatter slope towards the optical than seen in previous HST observations. We analyze our spectrum using both PICASO+Virga forward models and free retrievals. POSEIDON retrievals provide a well-constrained super-solar $\log$(H${}_2$O) abundance (-2.96${}_{-0.24}^{+0.31}$), breaking the degeneracy from the previous HST/Spitzer analysis. We verify our POSEIDON results with petitRADTRANS retrievals. Additionally, we constrain the abundance of $\log$(H${}^{-}$), -10.19${}_{-0.23}^{+0.30}$, finding that our model including H${}^{-}$ is preferred over our model without H${}^{-}$ to 5.1 $\sigma$. Furthermore, we constrain the $\log$(K) abundance (-8.07${}_{-0.52}^{+0.58}$) in WASP-17b's atmosphere for the first time using space-based observations. Our abundance constraints demonstrate the power of NIRISS SOSS's increased resolution, precision, and wavelength range to improve upon previous NIR space-based results. This work is part of a series of studies by our 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).

Accepted for Publication in the Astronomical Journal (AJ) on 19 November 2024; 37 Pages, 17 Figures, 7 Tables. This version adds 2 co-authors, updates affiliations/acknowledgements, and corrects minor typos. Zenodo link to data is at https://zenodo.org/records/14193061

References in corpus (45)

• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• Photochemically-produced SO${}_2$ in the atmosphere of WASP-39b
• The JWST Early Release Observations
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• ExoMol molecular line lists - XVI: The rotation-vibration spectrum of hot H${}_2$S
• Early Release Science of the exoplanet WASP-39b with JWST NIRISS
• Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H${}_2$O, Na, and K
• ExoMol line lists XVIII. The high temperature spectrum of VO
• ExoMol line lists -- XXXIX. Ro-vibrational molecular line list for CO${}_2$
• A consistent retrieval analysis of 10 Hot Jupiters observed in transmission
• Exoplanet Reflected Light Spectroscopy with PICASO
• A hybrid line list for CH${}_4$ and hot methane continuum
• Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra
• High temperature condensate clouds in super-hot Jupiter atmospheres
• Eureka!: An End-to-End Pipeline for JWST Time-Series Observations
• A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
• ExoMol molecular line lists: IX The spectrum of AlO
• PICASO 3.0: A One-Dimensional Climate Model for Giant Planets and Brown Dwarfs
• Optical constants of refractory oxides at high temperatures
• Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158
• Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H
• JWST/NIRISS reveals the water-rich "steam world" atmosphere of GJ 9827 d
• Empirical limb-darkening coefficients & transit parameters of known exoplanets from TESS
• POSEIDON: A Multidimensional Atmospheric Retrieval Code for Exoplanet Spectra
• Awesome SOSS: Transmission Spectroscopy of WASP-96b with NIRISS/SOSS
• TRIDENT: A Rapid 3D Radiative Transfer Model for Exoplanet Transmission Spectra
• Information Content Analysis for Selection of Optimal JWST Observing Modes for Transiting Exoplanet Atmospheres
• Near-Infrared Transmission Spectroscopy of HAT-P-18b with NIRISS: Disentangling Planetary and Stellar Features in the Era of JWST
• Water and an escaping helium tail detected in the hazy and methane-depleted atmosphere of HAT-P-18b from JWST NIRISS/SOSS
• Observability of signatures of transport-induced chemistry in clear atmospheres of hot gas giant exoplanets
• Awesome SOSS: Atmospheric Characterisation of WASP-96 b using the JWST Early Release Observations
• The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope -- III. Single Object Slitless Spectroscopy
• The calculated rovibronic spectrum of scandium hydride, ScH
• Potassium detection in the clear atmosphere of a hot-Jupiter: FORS2 transmission spectroscopy of WASP-17b
• ExoTiC-LD: thirty seconds to stellar limb-darkening coefficients
• Spectroscopic Time-series Performance of JWST/NIRSpec from Commissioning Observations
• A New Sedimentation Model for Greater Cloud Diversity in Giant Exoplanets and Brown Dwarfs
• On the Application of Bayesian Leave-One-Out Cross-Validation to Exoplanet Atmospheric Analysis
• APPLESOSS: A Producer of ProfiLEs for SOSS. Application to the NIRISS SOSS Mode
• A Comprehensive Analysis of WASP-17b's Transmission Spectrum from Space-Based Observations
• Exoplanet Spectroscopy with JWST NIRISS: Diagnostics and Case Studies
• ATOCA: an algorithm to treat order contamination. Application to the NIRISS SOSS mode
• An Information-Theoretic Approach to Optimize JWST Observations and Retrievals of Transiting Exoplanet Atmospheres
• JWST-TST DREAMS: Non-Uniform Dayside Emission for WASP-17b from MIRI/LRS

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