| Title: |
Detection of CO₂, CO, and H₂O in the atmosphere of the warm sub-Saturn HAT-P-12 b |
| Authors: |
Crouzet, Nicolas; Edwards, Billy; Konings, Thomas; Bouwman, Jeroen; Min, Michiel; Lagage, Pierre Olivier; Waters, Laurentius B.F.M.; Pye, John P.; Heinke, Linus; Guedel, Manuel; Henning, Thomas K.; Vandenbussche, Bart K.; Absil, Olivier; Argyriou, Ioannis; Barrado, David; Boccaletti, Anthony; Cossou, Alain; Coulais, Leen; Decin, Rene; Gastaud, Christophe; Patapis, Polychronis; id_orcid:0 000-0001-8718-3732 |
| Source: |
Astronomy & Astrophysics, 703 |
| Publisher Information: |
EDP Sciences |
| Publication Year: |
2025 |
| Collection: |
ETH Zürich Research Collection |
| Subject Terms: |
methods: observational; techniques: spectroscopic; eclipses; planets and satellites: atmospheres; planets and satellites: gaseous planet; planets and satellites: individual: HAT-P-12 b |
| Description: |
Context. The chemical composition of warm gas giant exoplanet atmospheres (with T eq < 1000 K) is not well known due to the lack of observational constraints. Aims. HAT-P-12 b is a warm, sub-Saturn-mass transiting exoplanet that is ideal for transmission spectroscopy. We aim to characterise its atmosphere and probe the presence of carbonaceous species using near-infrared observations. Methods. One transit of HAT-P-12 b was observed in spectroscopy with JWST NIRSpec in the 2.87–5.10 µm range with a resolving power of ~1000. The JWST data are combined with archival observations from HST WFC3 covering the 1.1–1.7 µm range. The data were analysed using two data reduction pipelines and two atmospheric retrieval tools. Atmospheric simulations using chemical forward models were performed to interpret the spectra. Results. CO 2 , CO, and H 2 O are detected at 12.2, 4.1, and 6.0 σ confidence, respectively. Their volume mixing ratios are consistent with an atmosphere of ~10× solar metallicity and production of CO 2 by photochemistry. CH 4 is not detected and seems to be lacking, which could be due to a high intrinsic temperature with strong vertical mixing or other phenomena. SO 2 is also not detected and its production seems limited by low upper atmosphere temperatures (~500 K at P ≲ 10 −3 bar derived from one-dimensional retrievals), insufficient to produce it in detectable quantities (≳ 800 K required according to photochemical models). H 2 S is marginally detected using one data analysis method, but not by the other. Retrievals indicate the presence of clouds between 2 and 11 mbar using one data analysis method, and between 5 and 269 mbar using the other. The derived C/O ratio is below unity, but is not well constrained. Conclusions. This study points towards an atmosphere for HAT-P-12 b that could be enriched in carbon and oxygen with respect to its host star, a possibly cold upper atmosphere that may explain the non-detection of SO 2 , and a CH 4 depletion that is yet to be fully understood. When including the ... |
| Document Type: |
article in journal/newspaper |
| File Description: |
application/application/pdf |
| Language: |
English |
| Relation: |
info:eu-repo/grantAgreement/SNF/Projekte MINT/200399; https://hdl.handle.net/20.500.11850/788440 |
| DOI: |
10.3929/ethz-c-000788440 |
| Availability: |
https://hdl.handle.net/20.500.11850/788440; https://doi.org/10.3929/ethz-c-000788440 |
| Rights: |
info:eu-repo/semantics/openAccess ; http://creativecommons.org/licenses/by/4.0/ ; Creative Commons Attribution 4.0 International |
| Accession Number: |
edsbas.108FE93E |
| Database: |
BASE |