FIESTA II。在傅立叶域中从系外行星多普勒频移中解开恒星和仪器的变化
FIESTA II. Disentangling stellar and instrumental variability from exoplanetary Doppler shifts in Fourier domain
摘要：
太阳系外行星的径向速度（RV）检测受到恒星光谱变化的挑战，可以模仿行星的存在，仪器的不稳定性可以进一步模糊检测。恒星和仪器的变化都可能使谱线轮廓发生扭曲，并被误解为明显的RV位移。我们提出了一种改进的FourIEr \textit{phase}光谱分析（FIESTA a.k.a. $\mathitϕ$ ESTA）来将由于线变形而引起的视在速度偏移与真实多普勒偏移分离。$\mathitϕ$ ESTA将恒星光谱的交叉关联函数（CCF）投影到截断的傅立叶基函数上。使用来自每个傅立叶模式的幅度和相位信息，我们可以跟踪不同CCF宽度尺度下的线变化，以鲁棒地识别和减轻RV污染的多个来源。例如，在我们对HARPS-N三年太阳资料的研究中，$\mathitϕ$ ESTA揭示了太阳自转效应、由于太阳磁周期、仪器不稳定性和视太阳自转速率变化而引起的长期趋势。对$\mathitϕ$ ESTA指标应用多元线性回归模型，我们将加权均方根噪声从1.89 m/s降低到0.98 m/s。此外，我们在$\mathitϕ$ ESTA指标中观察到$\sim$ 3天的滞后，与先前关于BIS和FWHM的研究结果相似。
英文摘要：
The radial velocity (RV) detection of exoplanets is challenged by stellar spectroscopic variability that can mimic the presence of planets and by instrumental instability that can further obscure the detection. Both stellar and instrumental changes can distort the spectral line profiles and be misinterpreted as apparent RV shifts. We present an improved FourIEr \textit{phase} SpecTrum Analysis (FIESTA a.k.a. $\mathitϕ$ESTA) to disentangle apparent velocity shifts due to a line deformation from a true Doppler shift. $\mathitϕ$ESTA projects stellar spectrum's cross correlation function (CCF) onto a truncated set of Fourier basis functions. Using the amplitude and phase information from each Fourier mode, we can trace the line variability at different CCF width scales to robustly identify and mitigate multiple sources of RV contamination. For example, in our study of the 3 years of HARPS-N solar data, $\mathitϕ$ESTA reveals the solar rotational effect, the long-term trend due to solar magnetic cycle, instrumental instability and apparent solar rotation rate changes. Applying a multiple linear regression model on $\mathitϕ$ESTA metrics, we reduce the weighted rms noise from 1.89 m/s to 0.98 m/s. In addition, we observe a $\sim$3 days lag in the $\mathitϕ$ESTA metrics, similar to the findings from previous studies on BIS and FWHM.
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