Refractory and Volatile Species in the UV-to-IR Transmission Spectrum of Ultra-hot Jupiter WASP-178b with HST and JWST

Abstract The atmospheres of ultra-hot Jupiters are unique compared to other planets because of the presence of both refractory and volatile gaseous species, enabling a new lens to constrain a planet’s composition, chemistry, and formation. WASP-178b is one such ultra-hot Jupiter that was recently found to exhibit enormous near-UV absorption between 0.2 and 0.4 μ m from some combination of Fe+, Mg, and SiO. Here, we present new IR observations of WASP-178b with the Hubble Space Telescope (HST) WFC3 and JWST NIRSpec G395H, providing novel measurements of the volatile species H 2 O and CO in WASP-178b’s atmosphere. Atmospheric retrievals find a range of compositional interpretations depending on which data set is retrieved, the type of chemistry assumed, and the temperature structure parameterization used due to the combined effects of thermal dissociation, the lack of volatile spectral features besides H 2 O and CO, and the relative weakness of H 2 O and CO themselves. Taken together with a new state-of-the-art characterization of the host star, our retrieval analyses suggests a solar to supersolar [O/H] and [Si/H], but subsolar [C/H], perhaps suggesting rock-laden atmospheric enrichment near the H 2 O ice line. To obtain meaningful abundance constraints for this planet, it was essential to combine the JWST IR data with short-wavelength HST observations, highlighting the ongoing synergy between the two facilities.

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Publication Details

Journal
The Astronomical Journal
Published
2025-04-24
DOI
https://doi.org/10.3847/1538-3881/adc117
Citations
6
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
6.93

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article

Refractory and Volatile Species in the UV-to-IR Transmission Spectrum of Ultra-hot Jupiter WASP-178b with HST and JWST

Katherine A. Bennett, Suzanne Norris, Henrique Reggiani, Amélie Gressier et al.
6 citations
The Astronomical Journal
Astro and Planetary Science
6.93
article

Refractory and Volatile Species in the UV-to-IR Transmission Spectrum of Ultra-hot Jupiter WASP-178b with HST and JWST

Katherine A. Bennett, Suzanne Norris, Henrique Reggiani, Amélie Gressier, Neale P. Gibson, Jamie Wilson, Kevin B. Stevenson, Patrick McCreery, T. M. Evans, Joshua D. Lothringer, Nikolay Nikolov, Néstor Espinoza, Zafar Rustamkulov, P. H. Hauschildt, David K. Sing, Hannah R. Wakeford, Cyril Gapp, Ceiligh Cacho-Negrete, Kevin C. Schlaufman, Brian Kehoe-Seamons
article en
6 citations

Abstract

Abstract The atmospheres of ultra-hot Jupiters are unique compared to other planets because of the presence of both refractory and volatile gaseous species, enabling a new lens to constrain a planet’s composition, chemistry, and formation. WASP-178b is one such ultra-hot Jupiter that was recently found to exhibit enormous near-UV absorption between 0.2 and 0.4 μ m from some combination of Fe+, Mg, and SiO. Here, we present new IR observations of WASP-178b with the Hubble Space Telescope (HST) WFC3 and JWST NIRSpec G395H, providing novel measurements of the volatile species H 2 O and CO in WASP-178b’s atmosphere. Atmospheric retrievals find a range of compositional interpretations depending on which data set is retrieved, the type of chemistry assumed, and the temperature structure parameterization used due to the combined effects of thermal dissociation, the lack of volatile spectral features besides H 2 O and CO, and the relative weakness of H 2 O and CO themselves. Taken together with a new state-of-the-art characterization of the host star, our retrieval analyses suggests a solar to supersolar [O/H] and [Si/H], but subsolar [C/H], perhaps suggesting rock-laden atmospheric enrichment near the H 2 O ice line. To obtain meaningful abundance constraints for this planet, it was essential to combine the JWST IR data with short-wavelength HST observations, highlighting the ongoing synergy between the two facilities.

The Astronomical JournalVol. 169(5)
Space Telescope Science Institute (US), Johns Hopkins University (US), Universität Hamburg (DE), Utah Valley University (US), Trinity College Dublin (IE), Heidelberg University (DE), University of Limerick (IE), Johns Hopkins University Applied Physics Laboratory (US), University of Bristol (GB), Max Planck Institute for Astronomy (DE), Gemini South Observatory (CL), Hamburger Fern-Hochschule (DE), Bristol Robotics Laboratory (GB), University of Newcastle Australia (AU)
Smithsonian Institution, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Vanderbilt University, Ohio State University, University of Utah, University of Washington, Johns Hopkins University, Carnegie Mellon University, University of Notre Dame, University of Portsmouth, New Mexico State University, National Computational Infrastructure, Astronomy Australia Limited, Space Telescope Science Institute, York University, University of Oxford, Australian National University, Monash University, Swinburne University of Technology, University of Melbourne, University of Queensland, Curtin University of Technology, Ministério da Ciência, Tecnologia e Inovação, Universidad Nacional Autónoma de México, Max-Planck-Institut für Astrophysik, Max-Planck-Institut für Astronomie, Office of Science, University of Colorado Boulder, Leibniz-Gemeinschaft, Australian Astronomical Optics-Macquarie, National Cancer Institute, Lawrence Berkeley National Laboratory
Openalex Percentile: Top 3%
Astro and Planetary Science
6.93
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