Atmospheric retrieval evidence for water isotopologue HDO on exoplanet WASP-39b
Fabian Gruebel, Karan Molaverdikhani, Barbara Ercolano, Katy L. Chubb, Paola Caselli, Tommaso Grassi, Rosa Arenales-Lope, Dwaipayan Dubey
Exzellenzcluster Origins, Garching, Germany · Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Germany · Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Germany · HH Wills Physics Laboratory, University of Bristol, Bristol, UK · Exzellenzcluster Origins, Garching, Germany · Exzellenzcluster Origins, Garching, Germany · Exzellenzcluster Origins, Garching, Germany · Exzellenzcluster Origins, Garching, Germany
astro-ph.EP
Submitted: 2026-07-21
Comments: Under review, comments welcome
Code: https://github.com/callumrollo/cmcrameri
License: http://creativecommons.org/licenses/by/4.0/
The gist: Hydrogen-isotopologues are commonly used to trace the chemical processing and origin of hydrogen-bearing species throughout the Universe, however, their abundance remains unconstrained for extrasolar
Terminology
Abstract
Hydrogen-isotopologues are commonly used to trace the chemical processing and origin of hydrogen-bearing species throughout the Universe, however, their abundance remains unconstrained for extrasolar planets. Here, we report atmospheric retrieval evidence for the deuterated water molecule HDO in an exoplanet atmosphere, retrieved from James Webb Space Telescope transmission spectra of the hot Jupiter WASP-39 b, resulting in a deuterium-to-hydrogen ratio in water of 4.0+1.3-1.1 times 10-3. The inferred value is substantially higher than those measured for the Solar System gas giants and overlaps numerically with values reported for some protostellar and inner Solar System environments. This enrichment may reflect either inherited water-rich material accreted beyond the snow line or isotopic processing in the observable atmosphere through transport, photochemistry, and subsequent escape.
Sources
- A new look into the atmospheric composition of WASP-39 b
- Atmospheric characterization of HIP 67522 b with VLT/CRIRES+. VLT/CRIRES+ suggests a heavier planet and hints at deuterium fractionation
- Investigating the Influence of Asymmetric Errors on Retrievals of Exoplanet Transmission Spectra
- Bayesian Model Comparison and Significance: Widespread Errors and how to Correct Them
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