On Atmospheric Retrievals of Exoplanets with Inhomogeneous Terminators
Publication Date
2022-07-01Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
American Astronomical Society
Language
en
Type
Article
This Version
VoR
Metadata
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Welbanks Camarena, L., & Nikku, M. (2022). On Atmospheric Retrievals of Exoplanets with Inhomogeneous Terminators. Astrophysical Journal https://doi.org/10.3847/1538-4357/ac6df1
Abstract
The complexity of atmospheric retrieval models is largely data-driven and
one-dimensional models have generally been considered adequate with current
data quality. However, recent studies have suggested that using 1D models in
retrievals can result in anomalously cool terminator temperatures and biased
abundance estimates even with existing transmission spectra of hot Jupiters.
Motivated by these claims and upcoming high-quality transmission spectra we
systematically explore the limitations of 1D models using synthetic and current
observations. We use 1D models of varying complexity, both analytic and
numerical, to revisit claims of biases when interpreting transmission spectra
of hot Jupiters with inhomogeneous terminator compositions. Overall, we find
the reported biases to be resulting from specific model assumptions rather than
intrinsic limitations of 1D atmospheric models in retrieving current
observations of asymmetric terminators. Additionally, we revise atmospheric
retrievals of the hot Jupiter WASP-43b ($T_{\rm eq}=1440$ K) and the ultra-hot
Jupiter WASP-103b ($T_{\rm eq}=2484$ K ) for which previous studies inferred
abnormally cool atmospheric temperatures. We retrieve temperatures consistent
with expectations. We note, however, that in the limit of extreme terminator
inhomogeneities and high data quality some atmospheric inferences may
conceivably be biased, although to a lesser extent than previously claimed. To
address such cases, we implement a 2D retrieval framework for transmission
spectra which allows accurate constraints on average atmospheric properties and
provides insights into the spectral ranges where the imprints of atmospheric
inhomogeneities are strongest. Our study highlights the need for careful
considerations of model assumptions and data quality before attributing biases
in retrieved estimates to unaccounted atmospheric inhomogeneities.
Keywords
350, The Solar System, Exoplanets, and Astrobiology
Sponsorship
Engineering and Physical Sciences Research Council (EP/P020259/1)
Identifiers
apjac6df1, ac6df1, aas36653
External DOI: https://doi.org/10.3847/1538-4357/ac6df1
This record's URL: https://www.repository.cam.ac.uk/handle/1810/338821
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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