BOWIE-ALIGN: <i>JWST</i> reveals hints of planetesimal accretion and complex sulphur chemistry in the atmosphere of the misaligned hot Jupiter WASP-15b

ABSTRACT We present a transmission spectrum of the misaligned hot Jupiter WASP-15b from 2.8–5.2 microns observed with JWST’s NIRSpec/G395H grating. Our high signal-to-noise data, which has negligible red noise, reveals significant absorption by H$_2$O ($4.2\sigma$) and CO$_2$ ($8.9\sigma$). From independent data reduction and atmospheric retrieval approaches, we infer that WASP-15b’s atmospheric metallicity is supersolar ($\gtrsim 15\times$ solar) and its carbon-to-oxygen ratio is consistent with solar, that together imply planetesimal accretion. Our general circulation model simulations for WASP-15b suggest that the carbon-to-oxygen ratio we measure at the limb is likely representative of the entire photosphere due to the mostly uniform spatial distribution of ${\text{H}}_{2}{\text{O}}$, ${\text{CO}}_{2}$, and CO. We additionally see evidence for absorption by SO$_2$ and absorption at 4.9 $\mu$m, for which the current leading candidate is OCS (carbonyl sulphide), albeit with several caveats. If confirmed, this would be the first detection of OCS in an exoplanet atmosphere and point towards complex photochemistry of sulphur-bearing species in the upper atmosphere. These are the first observations from the BOWIE-ALIGN survey which is using JWST’s NIRSpec/G395H instrument to compare the atmospheric compositions of aligned/low-obliquity and misaligned/high-obliquity hot Jupiters around F stars above the Kraft break. The goal of our survey is to determine whether the atmospheric composition differs across two populations of planets that have likely undergone different migration histories (disc versus disc-free) as evidenced by their obliquities (aligned versus misaligned).

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-02-03
DOI
https://doi.org/10.1093/mnras/staf208
Citations
19
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
21.94

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article

BOWIE-ALIGN: JWST reveals hints of planetesimal accretion and complex sulphur chemistry in the atmosphere of the misaligned hot Jupiter WASP-15b

Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie, Annabella Meech et al.
19 citations
Monthly Notices of the Royal Astronomical Society
Astro and Planetary Science
21.94
article

BOWIE-ALIGN: JWST reveals hints of planetesimal accretion and complex sulphur chemistry in the atmosphere of the misaligned hot Jupiter WASP-15b

Mercedes López‐Morales, Eva-Maria Ahrer, Duncan Christie, Annabella Meech, James E. Owen, Mason McCormack, Chloe Fisher, Jake Taylor, Maria Zamyatina, Richard A Booth, P. J. Wheatley, James Kirk, Anna B. T. Penzlin, Diana Powell, Daniel Thorngren, Shang‐Min Tsai, 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
19 citations

Abstract

ABSTRACT We present a transmission spectrum of the misaligned hot Jupiter WASP-15b from 2.8–5.2 microns observed with JWST’s NIRSpec/G395H grating. Our high signal-to-noise data, which has negligible red noise, reveals significant absorption by H$_2$O ($4.2\sigma$) and CO$_2$ ($8.9\sigma$). From independent data reduction and atmospheric retrieval approaches, we infer that WASP-15b’s atmospheric metallicity is supersolar ($\gtrsim 15\times$ solar) and its carbon-to-oxygen ratio is consistent with solar, that together imply planetesimal accretion. Our general circulation model simulations for WASP-15b suggest that the carbon-to-oxygen ratio we measure at the limb is likely representative of the entire photosphere due to the mostly uniform spatial distribution of ${\text{H}}_{2}{\text{O}}$, ${\text{CO}}_{2}$, and CO. We additionally see evidence for absorption by SO$_2$ and absorption at 4.9 $\mu$m, for which the current leading candidate is OCS (carbonyl sulphide), albeit with several caveats. If confirmed, this would be the first detection of OCS in an exoplanet atmosphere and point towards complex photochemistry of sulphur-bearing species in the upper atmosphere. These are the first observations from the BOWIE-ALIGN survey which is using JWST’s NIRSpec/G395H instrument to compare the atmospheric compositions of aligned/low-obliquity and misaligned/high-obliquity hot Jupiters around F stars above the Kraft break. The goal of our survey is to determine whether the atmospheric composition differs across two populations of planets that have likely undergone different migration histories (disc versus disc-free) as evidenced by their obliquities (aligned versus misaligned).

Monthly Notices of the Royal Astronomical SocietyVol. 537(4)
University of California, Riverside (US), Space Telescope Science Institute (US), University of Leeds (GB), Johns Hopkins University (US), Universidad de La Laguna (ES), Cornell University (US), University of Exeter (GB), University of Bristol (GB), University of Warwick (GB), University of Oxford (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), Imperial College London (GB)
Science and Technology Facilities Council
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Openalex Percentile: Top 0%
Astro and Planetary Science
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