Asymmetry and Dynamical Constraints in 2-Limbs Retrieval of WASP-39 b Inferring from JWST Data

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Main Authors: Chen, Zixin, Ji, Jianghui, Chen, Guo, Yan, Fei, Tan, Xianyu
Format: Preprint
Published: 2025
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author Chen, Zixin
Ji, Jianghui
Chen, Guo
Yan, Fei
Tan, Xianyu
author_facet Chen, Zixin
Ji, Jianghui
Chen, Guo
Yan, Fei
Tan, Xianyu
contents Transmission spectroscopy has provided unprecedented insight into the makeup of exoplanet atmospheres. A transmission spectrum contains contributions from a planet's morning and evening limbs, which can differ in temperature, composition and aerosol properties due to atmospheric circulation. While high-resolution ground-based observations have identified limb asymmetry in several ultra-hot/hot exoplanets, space-based studies of limb asymmetry are still in their early stages. The prevalence of limb asymmetry across a broad range of exoplanets remains largely unexplored. We conduct a comparative analysis of retrievals on transmission spectra, including traditional 1D approaches and four 2D models that account for limb asymmetry. Two of these 2D models include our newly proposed dynamical constraints derived from shallow-water simulations to provide physically-motivated temperature differences between limbs. Our analysis of WASP-39 b using JWST observations and previous combined datasets (HST, VLT, and Spitzer) strongly favors 2D retrievals over traditional 1D approaches, confirming significant limb asymmetry in this hot Jupiter. Within our 2D framework, unconstrained models recover larger temperature contrasts than dynamically-constrained models, with improved fits to specific spectral features, although Bayesian evidence cannot definitively distinguish between these 2D approaches. Our results support the presence of homogeneous C/O in both the morning and evening atmospheres, but with temperature differences leading to variations in clouds and hazes. Using this treatment, we can study a larger sample of hot Jupiters to gain insights into atmospheric limb asymmetries on these planets.
format Preprint
id arxiv_https___arxiv_org_abs_2504_00419
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Asymmetry and Dynamical Constraints in 2-Limbs Retrieval of WASP-39 b Inferring from JWST Data
Chen, Zixin
Ji, Jianghui
Chen, Guo
Yan, Fei
Tan, Xianyu
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Solar and Stellar Astrophysics
Atmospheric and Oceanic Physics
Space Physics
Transmission spectroscopy has provided unprecedented insight into the makeup of exoplanet atmospheres. A transmission spectrum contains contributions from a planet's morning and evening limbs, which can differ in temperature, composition and aerosol properties due to atmospheric circulation. While high-resolution ground-based observations have identified limb asymmetry in several ultra-hot/hot exoplanets, space-based studies of limb asymmetry are still in their early stages. The prevalence of limb asymmetry across a broad range of exoplanets remains largely unexplored. We conduct a comparative analysis of retrievals on transmission spectra, including traditional 1D approaches and four 2D models that account for limb asymmetry. Two of these 2D models include our newly proposed dynamical constraints derived from shallow-water simulations to provide physically-motivated temperature differences between limbs. Our analysis of WASP-39 b using JWST observations and previous combined datasets (HST, VLT, and Spitzer) strongly favors 2D retrievals over traditional 1D approaches, confirming significant limb asymmetry in this hot Jupiter. Within our 2D framework, unconstrained models recover larger temperature contrasts than dynamically-constrained models, with improved fits to specific spectral features, although Bayesian evidence cannot definitively distinguish between these 2D approaches. Our results support the presence of homogeneous C/O in both the morning and evening atmospheres, but with temperature differences leading to variations in clouds and hazes. Using this treatment, we can study a larger sample of hot Jupiters to gain insights into atmospheric limb asymmetries on these planets.
title Asymmetry and Dynamical Constraints in 2-Limbs Retrieval of WASP-39 b Inferring from JWST Data
topic Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
Solar and Stellar Astrophysics
Atmospheric and Oceanic Physics
Space Physics
url https://arxiv.org/abs/2504.00419