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

临边暗化是恒星和行星系统研究领域中的一个重要物理参数，也就是可见星盘上亮度沿径向的变化。不幸的是，只有太阳才有可能直接测量极光变暗，而恒星的极光变暗通常是从大气模型中推断出来的。由于发现了许多围绕类太阳恒星的行星，特别是利用凌日方法，肢体暗化的研究经历了某种形式的复兴。边缘暗化与大多数其他凌日参数显示出很强的相关性，因此大多数系外行星观测者在凌日模型中将恒星边缘暗化视为一个“讨厌”的参数。但是，如果数据质量足够高，边缘暗化可以在行星日食期间直接测量到。此外，也不太为人所知的是，肢体暗化对于透射谱领域也是非常重要的，因此对于行星际大气及其化学成分的所有研究也是非常重要的。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方法研究太阳系外行星的影响，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模型大气尽可能真实地进行过境光曲线模拟，并开发分析方法，允许以尽可能独立于边缘变暗的方式推导出过境参数。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边缘暗化问题，对于在旨在揭示系外行星大气光谱特征的高分辨率透射谱中区分行星和恒星信号来说，这方面的良好知识是绝对必要的。为了完成我们的研究项目，我们计划调查快速自转对主星和行星扁率的影响。

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.