BOWIE-ALIGN: weak spectral features in KELT-7b’s <i>JWST</i> NIRSpec/G395H transmission spectrum imply a high cloud deck or a low-metallicity atmosphere

ABSTRACT Hot Jupiters and their atmospheres are prime targets for transmission spectroscopy due to their extended atmospheres and the corresponding large signal-to-noise, providing the best possible constraints for the atmospheric carbon-to-oxygen (C/O) ratio and metallicity of exoplanets. Within BOWIE-ALIGN, we aim to compare JWST spectra of a sample of orbitally aligned and misaligned hot Jupiters orbiting F-type stars to probe the link between hot Jupiter atmospheres and planet formation history. Here, we present a near-infrared transmission spectrum of the aligned planet KELT-7b using one transit observed with JWST NIRSpec/G395H. We find weak features, only tentative evidence for H$_2$O and CO$_2$ in the atmosphere of KELT-7b. This poses a challenge to constrain the atmospheric properties of KELT-7b and two possible scenarios emerge from equilibrium chemistry and free chemistry retrievals: a high-altitude cloud deck muting all features or an extremely low metallicity atmosphere, respectively. The retrieved C/O ratios from our data reductions range from $0.43{\!-\!}0.74$, while the atmospheric metallicity is suggested to be solar to super-solar ($1{\!-\!}16 \times$ solar). Although these wide constraints prevent detailed conclusions about KELT-7b’s formation history, a solar-to-super-solar metallicity would imply the accretion of solid material during its formation, which is valuable information for the survey’s wider goals of understanding the relative importance of gaseous to solid accretion.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-09-16
DOI
https://doi.org/10.1093/mnras/staf1535
Citations
2
Primary Topic
Calibration and Measurement Techniques
Type
article
Field-Weighted Citation Impact
9.99

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article

BOWIE-ALIGN: weak spectral features in KELT-7b’s JWST NIRSpec/G395H transmission spectrum imply a high cloud deck or a low-metallicity atmosphere

Carlos Gascón, Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie et al.
2 citations
Monthly Notices of the Royal Astronomical Society
Calibration and Measurement Techniques
9.99
article

BOWIE-ALIGN: weak spectral features in KELT-7b’s JWST NIRSpec/G395H transmission spectrum imply a high cloud deck or a low-metallicity atmosphere

Carlos Gascón, Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie, Annabella Meech, James E. Owen, Mason McCormack, Maria Zamyatina, Richard A Booth, P. J. Wheatley, J. K. Barstow, James Kirk, Anna B. T. Penzlin, Daniel T. Valentine, Nathan J. Mayne, Lili Alderson, Vatsal Panwar, P. Mollière, Denis E. Sergeev, Hannah R. Wakeford, E. Esparza-Borges, Alastair B Claringbold, Charlotte Fairman
article en
2 citations

Abstract

ABSTRACT Hot Jupiters and their atmospheres are prime targets for transmission spectroscopy due to their extended atmospheres and the corresponding large signal-to-noise, providing the best possible constraints for the atmospheric carbon-to-oxygen (C/O) ratio and metallicity of exoplanets. Within BOWIE-ALIGN, we aim to compare JWST spectra of a sample of orbitally aligned and misaligned hot Jupiters orbiting F-type stars to probe the link between hot Jupiter atmospheres and planet formation history. Here, we present a near-infrared transmission spectrum of the aligned planet KELT-7b using one transit observed with JWST NIRSpec/G395H. We find weak features, only tentative evidence for H$_2$O and CO$_2$ in the atmosphere of KELT-7b. This poses a challenge to constrain the atmospheric properties of KELT-7b and two possible scenarios emerge from equilibrium chemistry and free chemistry retrievals: a high-altitude cloud deck muting all features or an extremely low metallicity atmosphere, respectively. The retrieved C/O ratios from our data reductions range from $0.43{\!-\!}0.74$, while the atmospheric metallicity is suggested to be solar to super-solar ($1{\!-\!}16 \times$ solar). Although these wide constraints prevent detailed conclusions about KELT-7b’s formation history, a solar-to-super-solar metallicity would imply the accretion of solid material during its formation, which is valuable information for the survey’s wider goals of understanding the relative importance of gaseous to solid accretion.

Monthly Notices of the Royal Astronomical SocietyVol. 543(3)
Space Telescope Science Institute (US), Planetary Science Institute (US), University of Leeds (GB), Universidad de La Laguna (ES), The Open University (GB), Cornell University (US), University of Exeter (GB), University of Bristol (GB), University of Warwick (GB), University of Chicago (US), Max Planck Institute for Astronomy (DE), Université Bourgogne Franche-Comté (FR), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Canarias (ES), Bristol Robotics Laboratory (GB), Imperial College London (GB), Ludwig-Maximilians-Universität München (DE)
National Aeronautics and Space Administration, Space Telescope Science Institute, Government of the United Kingdom, UK Research and Innovation, Leverhulme Trust, Imperial College London, European Commission, HORIZON EUROPE Framework Programme, Science and Technology Facilities Council
Openalex Percentile: Top 2%
Calibration and Measurement Techniques
9.99
DOIOpen Access PDFOpenAlex
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