On the Dayside Atmosphere of WASP-12b

The atmospheric structure of WASP-12b has been hotly contested for years, with disagreements on the presence of a thermal inversion as well as the carbon-to-oxygen ratio, C/O, due to retrieved abundances of H 2 O, CO 2 , and other included species such as HCN and C 2 H 2 . Previously, these difficul...

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Bibliographic Details
Published in:The Astrophysical journal 2022-06, Vol.931 (2), p.86
Main Authors: Himes, Michael D., Harrington, Joseph
Format: Article
Language:English
Subjects:
Astrophysics
Atmosphere
Atmospheric models
Atmospheric structure
Carbon dioxide
Dissociation
Exoplanet astronomy
Exoplanet atmospheres
Exoplanet atmospheric composition
Exoplanet systems
Exoplanets
Extrasolar planets
Hot Jupiters
Modelling
Oxygen
Thermal dissociation
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Summary:The atmospheric structure of WASP-12b has been hotly contested for years, with disagreements on the presence of a thermal inversion as well as the carbon-to-oxygen ratio, C/O, due to retrieved abundances of H 2 O, CO 2 , and other included species such as HCN and C 2 H 2 . Previously, these difficult-to-diagnose discrepancies have been attributed to model differences; assumptions in these models were thought to drive retrievals toward different answers. Here, we show that some of these differences are independent of model assumptions and are instead due to subtle differences in the inputs, such as the eclipse depths and line-list databases. We replicate previously published retrievals and find that the retrieved results are data driven and are mostly unaffected by the addition of species such as HCN and C 2 H 2 . We also propose a new physically motivated model that takes into consideration the formation of H − via the thermal dissociation of H 2 O and H 2 at the temperatures reached in the dayside atmosphere of WASP-12b, but the data’s current resolution does not support its inclusion in the atmospheric model. This study raises the concern that other exoplanet retrievals may be similarly sensitive to slight changes in the input data.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac1e9f