Stellar Contamination in Exoplanet Transmission Spectra

该项目的目的是限制恒星不均匀性（即斑点和光斑）对系外行星透射光谱的污染，以便能够更准确地进行系外行星大气检索。首先，用磁流体动力学模拟的恒星大气正演模型将在不同的平均磁场和不同的光谱类型下进行。每个模拟的斑点和光斑的覆盖分数和对比将使污染水平已知。模拟还将探讨不同活动纬度对斑点和光斑出现的影响。然后，将对一颗标准系外行星穿越每一颗模拟恒星的模拟凌日数据进行大气检索。这将允许已知污染对每个导出的透射光谱的影响受到不同磁场强度和恒星光谱类型的限制。然后，这项调查的结果将应用于实际的过境数据。

The purpose of the project is to constrain the contamination of exoplanet transmission spectra from stellar inhomogeneities (i.e., spots and faculae) in order that exoplanet atmospheric retrievals can be performed with greater accuracy. To begin, forward modelling of stellar atmospheres with magneto-hydrodynamic simulations will be done with a varying mean magnetic field and for different spectral types. The covering fraction and contrasts of the spots and faculae for each simulation will enable the contamination level to be known. The simulations will also explore the effect of having different active latitudes for spot and faculae emergence on the degree of contamination. Atmospheric retrievals will then be done to simulated transit data for a standard exoplanet transiting each of the stellar simulations. This will allow the effect of the known contamination on each of the derived transmission spectra to be constrained for varying magnetic field strength and stellar spectral type. The findings from this investigation will then be applied to real transit data.