Exploring the effects of limb darkening on multi-wavelength photometric and spectroscopic studies of extrasolar planets

临边变暗，即可见星盘在径向上的亮度变化，是恒星和行星系统研究领域的一个重要物理参数。不幸的是，只能直接测量太阳的边缘变暗，而恒星的边缘变暗通常是从大气模型中推断出来的。由于在类太阳恒星周围发现了许多行星，特别是用凌日法，对翼暗的研究经历了某种复兴。临边变暗确实与大多数其他凌日参数有很强的相关性，因此大多数系外行星观测者在凌日模型中将恒星临边变暗视为一个“讨厌的”参数。然而，如果数据质量足够高，在行星日食期间可以直接测量到临边变暗。此外，鲜为人知的是，翼缘变暗对透射光谱学领域也非常重要，因此对所有系外行星大气及其化学成分的研究也非常重要。因此，现在是重新审视恒星边缘变暗的时候了，特别关注它对使用凌日法研究系外行星的影响，这是这里提出的研究项目的中心主题。我们特别建议使用最新的恒星大气模型尽可能真实地进行凌日光曲线模拟，并开发分析方法，以尽可能独立于边缘变暗的方式推导凌日参数。这些分析方法将应用于现有的档案数据，同时，我们计划研究JWST在太阳系外行星凌日研究中的潜力。另一个主要问题是微分翼变暗，这对于在高分辨率透射光谱中解开行星和恒星信号是绝对必要的，目的是揭示系外行星大气的光谱特征。为了完成我们的研究项目，我们计划研究主星和行星的扁率对快速旋转造成的影响。

Limb darkening, i.e., the brightness change on the visible stellar disk in radial direction, is an important physical parameter in the research area of stellar and planetary systems. Unfortunately, a direct measurement of limb darkening is only possible for the Sun, while limb darkening for stars is usually inferred from atmosphere models. Due to the discovery of many planets around solar-like stars especially with the transit method, the study of the limb darkening has undergone some kind of renaissance. Limb darkening does show strong correlations with most other transit parameters, therefore most exoplanet observers treat stellar limb darkening as a ``nuisance'' parameter in their transit modeling.However, limb darkening can directly be measured during a planetary eclipse, if the data quality is sufficiently high. Furthermore and less well known, limb darkening is also very important for the area of transmission spectroscopy and consequently for all studies of the exoplanetary atmospheres and their chemical composition. The time has therefore come to take a fresh look at stellar limb darkening with a specific focus on its influence on the study of extrasolar planets using the transit method, which is the central theme of the here proposed research project. We specifically propose to carry out transit light curve simulations as realistically as possible using most recent stellar model atmospheres and develop analysis methods that allow to derive the transit parameters in a fashion as independently from limb darkening as possible. These analysis methods shall be applied to existing archival data, and at the same time, we plan to study the potential of JWST for transit studies of extrasolar planets. A further major issue is that of differential limb darkening, a good knowledge of which is absolutely essential to disentangle planetary and stellar signals in high resolution transmission spectroscopy aimed at revealing spectroscopic signatures of exoplanetary atmospheres. To complete our research project we plan to investigate the influence of oblateness of both the host star and the planet caused by fast rotation.