The Sun’s center-to-limb variation and its impact on radial velocity and transit observations

用径向速度法寻找系外行星、研究系外行星的大气层以及理解恒星和太阳的表面对流，都需要对恒星表面光谱有准确的了解。为了找到并正确解释系外行星的细微特征，必须非常详细地了解表面和时间上光谱线轮廓的变化。从空间分辨的观测中获得的太阳线轮廓的经验信息只能从直接观测中获得，但只有有限的数据可以达到所需的精度，而且只有少数光谱线。我们建议在太阳表面不同翼角的全光学和近红外波长范围（450-2300\,nm）获得不同磁场强度下太阳的参考观测值。我们将对不同翼角和磁场下的对流蓝移进行详细分析，这些数据将为寻找系外行星和分析系外行星大气的方法提供重要信息。数据应以电子地图集的形式提供给科学界。我们将提供一个工具来模拟具有参数化表面特性的恒星的线轮廓和rv，并用于凌日模拟，我们将应用该工具来存档来自恒星的径向速度数据，以搜索隐藏在恒星固有变异性中的行星特征。

Accurate knowledge about stellar surface spectra is required for the search for extrasolar planets with the radial velocity method, the investigation of exoplanet atmospheres, and for understanding surface convection in stars and the Sun. The variability of spectral line profiles across the surface and in time must be understood in great detail in order to find and correctly interpret the subtle signatures of extrasolar planets. Empirical information about line profiles from spatially resolved observations can only be obtained for the Sun from direct observations, but only limited data at the required accuracy are available and only for a small number of spectral lines. We propose to obtain reference observations of the Sun at different magnetic field strengths for the full optical and near-infrared wavelength range (450-2300\,nm) across the solar surface at different limb angles. We will perform a detailed analysis of convective blueshift for different limb angles and magnetic fields, and the data will provide crucial information to make progress in the methodologies used for the search for exoplanets and the analysis of exoplanet atmospheres. The data shall be made available in the form of electronic atlases to the scientific community. We will provide a tool for the simulation of line profiles and RVs in stars with parameterized surface properties and for transit simulations, and we will apply the tool to archive radial velocity data from stars to search for planetary signatures hidden by intrinsic stellar variability.