在恒星黑子存在的情况下，从入口和出口持续时间的鲁棒凌日系外行星半径
Robust Transiting Exoplanet Radii in the Presence of Starspots from Ingress and Egress Durations
摘要：
我们通常从凌日深度测量凌日系外行星的半径，凌日深度由行星和恒星的横截面积之比给出。然而，如果一颗恒星的暗星斑（或亮区）分布在整个凌日弦上，凌日深度将偏向较小（较大）的值，因此如果不考虑的话，推断的行星半径将较小（较大）。我们重新参数化的过境光变曲线，占“自污染”的光球不均匀性分裂成两个参数的参数$R_p/R_\star$：一个半径比-控制的持续时间的入口和出口-和另一个测量可能污染的过境深度。我们表明，这是相当于第二颗星（正或负通量）的污染的配方，它是敏感的恒星光球的时间稳定的不均匀性。我们使用合成光变曲线的斑点星在高信号噪声表明，从测量的入口/出口持续时间恢复的半径可以恢复的真实半径行星过境斑点星与轴对称斑点分布，如果边缘变暗参数是精确已知的。我们拟合了开普勒和斯皮策10颗行星的时间平均高信噪比过境光变曲线，以测量行星半径并寻找斑点分布的证据。我们发现，该样品有一系列的测量深度和入口持续时间是自相一致的，没有提供强有力的证据污染的斑点。然而，有证据表明开普勒-17上的恒星黑子被遮蔽，相对明亮的区域被开普勒-412和HD 80606的行星遮蔽。詹姆斯·韦伯太空望远镜的未来观测可能使这项技术能够在恒星不均匀性存在的情况下产生精确的行星半径。
英文摘要：
We typically measure the radii of transiting exoplanets from the transit depth, which is given by the ratio of cross-sectional areas of the planet and star. However, if a star has dark starspots (or bright regions) distributed throughout the transit chord, the transit depth will be biased towards smaller (larger) values, and thus the inferred planet radius will be smaller (larger) if unaccounted for. We reparameterize the transit light curve to account for "self-contamination" by photospheric inhomogeneities by splitting the parameter $R_p/R_\star$ into two parameters: one for the radius ratio -- which controls the duration of ingress and egress -- and another which measures the possibly contaminated transit depth. We show that this is equivalent to the formulation for contamination by a second star (with positive or negative flux), and that it is sensitive to time-steady inhomogeneity of the stellar photosphere. We use synthetic light curves of spotted stars at high signal-to-noise to show that the radius recovered from measurement of the ingress/egress duration can recover the true radii of planets transiting spotted stars with axisymmetric spot distributions if the limb-darkening parameters are precisely known. We fit time-averaged high signal-to-noise transit light curves from Kepler and Spitzer of ten planets to measure the planet radii and search for evidence of spot distributions. We find that this sample has a range of measured depths and ingress durations which are self-consistent, providing no strong evidence for contamination by spots. However, there is suggestive evidence for occultation of starspots on Kepler-17, and that relatively bright regions are occulted by the planets of Kepler-412 and HD 80606. Future observations with the James Webb Space Telescope may enable this technique to yield accurate planetary radii in the presence of stellar inhomogeneities.
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