发表机构
University of Bristol; HH Wills Physics Laboratory; Max Planck Institute for Astronomy (MPIA); Department of Physics and Astronomy, Faculty of Environment, Science and Economy, University of Exeter; Imperial College London; Center for Space and Habitability, University of Bern（布里斯托大学; HH威尔斯物理实验室; 马克斯·普朗克天文学研究所; 埃克塞特大学环境、科学与经济学院物理与天文系; 帝国理工学院; 伯尔尼大学太空与宜居性中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过JWST NIRCam观测和1.5D反演，发现热木星HD 209458 b晨昏与黄昏临边在云属性上存在显著不对称，而温度与主要化学丰度均匀，凸显多维建模对减轻1D反演偏差的重要性。
AI 中文摘要
我们重新分析了热木星HD 209458 b的JWST NIRCam F322W2/F444W凌星观测数据，以提取晨昏和黄昏的透射光谱。为了确定凌星光变曲线中的不对称性是否源于大气结构，我们通过对存档的凌星和径向速度数据的重新分析，精化了HD 209458系统参数。随后，我们使用两个独立的光变曲线建模框架Harmonica和catwoman提取临边分辨光谱，两者得出一致的结果。我们使用1D和1.5D（即对行星每个临边独立建模的检索）大气反演来解释透射光谱。从我们的1.5D自由化学反演中，我们发现模型强烈偏好（Delta ln Z = 2.81 +/- 0.49）晨昏和黄昏临边独立检索，而非共享大气参数，尽管这需要额外的自由参数。这种不对称性在检索到的云属性中最为显著，与预测纵向变化云分布的3D大气环流模型一致，在CH4和CO丰度中程度稍弱。相比之下，H2O和CO2丰度以及等温温度结构在两个临边之间基本保持一致。同样，我们的1.5D平衡化学反演揭示了临边之间成分均匀，同时黄昏临边相对于晨昏临边略微更热。虽然检索到的温度、化学丰度、金属丰度和碳氧比（C/O）在两个临边之间均匀，但它们与我们的1D反演结果存在显著差异，凸显了多维建模在减轻1D反演偏差中的重要性。
英文摘要
We present a reanalysis of JWST NIRCam F322W2/F444W transit observations of the hot Jupiter HD 209458 b to extract morning and evening transmission spectra. To determine whether asymmetries in the transit light curves arise from atmospheric structure, we refine the HD 209458 system parameters through a reanalysis of archival transit and radial velocity data. We then extract limb-resolved spectra using two independent light curve modelling frameworks, Harmonica and catwoman,which yield consistent results. We interpret the transmission spectra using both 1D and 1.5D (i.e.,retrievals in which each limb of the planet is modelled independently) atmospheric retrievals. From our 1.5D free-chemistry retrievals, we find a strong preference (Delta ln Z = 2.81 +/- 0.49) for a model in which the morning and evening limbs are retrieved independently over one in which they share atmospheric parameters, despite the additional free parameters this requires. This asymmetry is most pronounced in the retrieved cloud properties, consistent with 3D atmospheric circulation models that predict longitudinally varying cloud distributions, and to a lesser extent in the CH4 and CO abundances. In contrast, the H2O and CO2 abundances and the isothermal temperature structure remain largely consistent between limbs. Similarly, our 1.5D equilibrium chemistry retrieval reveals a uniform composition between the limbs, alongside a marginally hotter evening limb relative to the morning limb. While the retrieved temperatures, chemical abundances, metallicities and carbon-to-oxygen ratios (C/O) are uniform across both limbs, they exhibit significant differences from our 1D retrieval results, highlighting the importance of multidimensional modelling in mitigating 1D retrieval biases.
Comments15 pages, 8 figures (excl. Appendix). Accepted for publication in the Astrophysical Journal Letters
