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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2501.08463 |
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| _version_ | 1866910819858513920 |
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| author | Bangera, Nidhi Helling, Christiane Guilluy, Gloria Cubillos, Patricio Fossati, Luca Giacobbe, Paolo Rimmer, Paul Kitzmann, Daniel |
| author_facet | Bangera, Nidhi Helling, Christiane Guilluy, Gloria Cubillos, Patricio Fossati, Luca Giacobbe, Paolo Rimmer, Paul Kitzmann, Daniel |
| contents | High-resolution transmission spectroscopy of the warm gas-giant WASP-69b has revealed the presence of H2O, CO, CH4, NH3, and C2H2 in its atmosphere. This study investigates the impact of vertical diffusion and photochemistry on its atmospheric composition, with a focus on the detected species plus HCN and CO2, to constrain the atmospheric C/O ratio. We utilize non-equilibrium gas-phase simulations to conduct a parameter study for vertical diffusion strength, local gas temperature, and C/O ratio. Our results indicate that a carbon-rich atmosphere enhances CH4 and C2H2 concentrations, while NH3 undergoes chemical conversion into HCN in carbon-rich, high-temperature environments. Consequently, HCN is abundantly produced in such atmospheres, though its strong spectral features remain undetected in WASP-69b. Photochemical production of HCN and C2H2 is highly sensitive to vertical diffusion strength, with weaker diffusion resulting in higher concentrations. Cross-correlation of synthetic spectra with observed data shows that models with C/O=2 best match observations, but models with C/O=0.55 and 0.9 lead to statistically equivalent fits, leaving the C/O ratio unconstrained. We highlight the importance of accurately modeling NH3 quenching at pressures greater than 100 bars. Models for WASP-69b capped at 100 bars bias cross-correlation fits towards carbon-rich values. We suggest that if the atmosphere of WASP-69b is indeed carbon-rich with a solar metallicity, future observations should reveal the presence of HCN. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_08463 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Kinetic and photochemical disequilibrium in the potentially carbon-rich atmosphere of the warm-Jupiter WASP-69b Bangera, Nidhi Helling, Christiane Guilluy, Gloria Cubillos, Patricio Fossati, Luca Giacobbe, Paolo Rimmer, Paul Kitzmann, Daniel Earth and Planetary Astrophysics High-resolution transmission spectroscopy of the warm gas-giant WASP-69b has revealed the presence of H2O, CO, CH4, NH3, and C2H2 in its atmosphere. This study investigates the impact of vertical diffusion and photochemistry on its atmospheric composition, with a focus on the detected species plus HCN and CO2, to constrain the atmospheric C/O ratio. We utilize non-equilibrium gas-phase simulations to conduct a parameter study for vertical diffusion strength, local gas temperature, and C/O ratio. Our results indicate that a carbon-rich atmosphere enhances CH4 and C2H2 concentrations, while NH3 undergoes chemical conversion into HCN in carbon-rich, high-temperature environments. Consequently, HCN is abundantly produced in such atmospheres, though its strong spectral features remain undetected in WASP-69b. Photochemical production of HCN and C2H2 is highly sensitive to vertical diffusion strength, with weaker diffusion resulting in higher concentrations. Cross-correlation of synthetic spectra with observed data shows that models with C/O=2 best match observations, but models with C/O=0.55 and 0.9 lead to statistically equivalent fits, leaving the C/O ratio unconstrained. We highlight the importance of accurately modeling NH3 quenching at pressures greater than 100 bars. Models for WASP-69b capped at 100 bars bias cross-correlation fits towards carbon-rich values. We suggest that if the atmosphere of WASP-69b is indeed carbon-rich with a solar metallicity, future observations should reveal the presence of HCN. |
| title | Kinetic and photochemical disequilibrium in the potentially carbon-rich atmosphere of the warm-Jupiter WASP-69b |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2501.08463 |