Using the Sun to estimate Earth-like planets detection capabilities - I. Impact of cold spots
Using the Sun to estimate Earth-like planets detection capabilities - I. Impact of cold spots
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DOI：
10.1051/0004-6361/200913071
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发表时间：
2010-01
影响因子：
6.5
通讯作者：
A. Lagrange;M. Desort;N. Meunier
中科院分区：
文献类型：
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作者：
A. Lagrange;M. Desort;N. Meunier
目标。斑点和斑块产生的恒星活动会影响径向速度（RV）特征。因为即使是低活动度的恒星也会产生这样的信号，因此确定它如何影响我们检测小行星信号（例如由地球质量的行星在宜居带（HZ）中产生的信号）的能力至关重要。在最近的一篇论文中，我们研究了类日斑的影响。我们的目的是调查斑块的额外影响。方法。我们利用太阳周期中的点和斑特性来推导出如果太阳处于边缘时将观测到的 RV。 RV 信号来自斑点和斑块的光度贡献以及斑块中对流蓝移的衰减。我们分析了不同活动水平下 RV 信号的特性，并将其与常用的活动指标（如光度测定和 Ca 指数）进行比较。我们还将其与位于赫兹区的地球质量行星产生的信号进行了比较。结果。我们发现斑点和斑点对 RV 信号的光度贡献部分相互平衡，因此残留信号与斑点信号相当。然而，对流蓝移衰减造成的斑块贡献在总信号中占主导地位，整个太阳周期的幅度约为 8-10 m/s。短期变化也显着大于斑点和斑块光度测定的贡献。从长远来看，这种贡献与 Ca 指数密切相关，这可能是区分恒星活动和行星的一种方法。结论。斑块和斑点的光度贡献提供了非常好的时间采样和信噪比，因此不应妨碍对赫兹区中地球质量行星的探测。然而，对流的贡献使得这种直接检测变得不可能，除非它的影响可以通过仍然需要找到的方法来校正。我们表明，如果灵敏度足够好，例如通过使用活动指标，则可以识别对流贡献。
Aims. Stellar activity produced by spots and plages affects the radial velocity (RV) signatures. Because even low activity stars would produce such a signal, it is crucial to determine how it influences our ability to detect small planetary signals such as those produced by Earth-mass planets in the habitable zone (HZ). In a recent paper, we investigated the impact of sunlike spots. We aim here to investigate the additional impact of plages. Methods. We used the spot and plage properties over a solar cycle to derive the RV that would be observed if the Sun was seen edgeon. The RV signal comes from the photometric contribution of spots and plages and from the attenuation of the convective blueshift in plages. We analyzed the properties of the RV signal at different activity levels and compared it with commonly used activity indicators such as photometry and the Ca index. We also compared it with the signal that would be produced by an Earth-mass planet in the HZ. Results. We find that the photometric contributions of spots and plages to the RV signal partially balance each other out, so that the residual signal is comparable to the spot signal. However, the plage contribution due to the convective blueshift attenuation dominates the total signal, with an amplitude over the solar cycle of about 8–10 m/s. Short-term variations are also significantly greater than the spot and plage photometric contribution. This contribution is very strongly correlated with the Ca index on the long term, which may be a way to distinguish between stellar activity and a planet. Conclusions. Providing a very good temporal sampling and signal-to-noise ratio, the photometric contribution of plages and spots should not prevent detection of Earth-mass planets in the HZ. However, the convection contribution makes such a direct detection impossible, unless its effect can be corrected for by methods that still need to be found. We show that it is possible to identify the convection contribution if the sensitivity is good enough, for example, by using activity indicators.