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

恒星表面光谱的精确知识是用径向速度法寻找太阳系外行星、研究太阳系外行星大气以及了解恒星和太阳表面对流所必需的。为了发现和正确解释太阳系外行星的微妙特征，必须非常详细地了解整个表面和时间上光谱线轮廓的变化。从空间分辨观测得到的谱线剖面的经验信息只能从直接观测中获得，但在所需的准确度上只能得到有限的数据，而且只能得到少数谱线的数据。我们建议在不同的磁场强度下获得太阳的参考观测，在整个太阳表面的光学和近红外波长范围（450- 2300 nm）在不同的边缘角。我们将对不同边缘角度和磁场的对流蓝移进行详细分析，这些数据将为搜索系外行星和分析系外行星大气的方法学取得进展提供关键信息。这些数据应以电子地图的形式提供给科学界。我们将提供一个工具，用于模拟线轮廓和RV在恒星参数化的表面特性和过境模拟，我们将应用该工具存档径向速度数据从恒星搜索隐藏的行星签名恒星的内在变化。

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.