半人马座$α$ B变样：K矮星中的探测斑和恒星活动
The Changing Face of $α$ Centauri B: Probing plage and stellar activity in K-dwarfs
摘要：
恒星活动的详细知识对于理解恒星发电机至关重要，并且将系外行星径向速度检测极限推向地球模拟确认。我们直接比较档案HARPS光谱在$α$ Cen B的活动周期的最小值时，一个高活性状态时，清晰的旋转调制的$\log{R'_{HK}}$是可见的。相对于非活性光谱，我们发现了大量的窄赝发射功能的强度旋转调制的活性光谱。这些特征最有可能来源于斑、斑点或两者的组合。它们还显示$\sim$ 300 m s $^{-1}$的径向速度变化-与恒星表面旋转的活动区域一致。此外，我们看到的证据表明，一些线起源于“活跃的完美”光球出现更广泛的相对于“不活跃的完美”的情况。这可能是由于例如磁亮点对这些线的贡献增强，这然后导致额外的线加宽。更详细的分析可能使未来使用单光谱测量谱斑和斑点覆盖率成为可能。
英文摘要：
A detailed knowledge of stellar activity is crucial for understanding stellar dynamos, as well as pushing exoplanet radial-velocity detection limits towards Earth analogue confirmation. We directly compare archival HARPS spectra taken at the minimum in $α$ Cen B's activity cycle to a high-activity state when clear rotational modulation of $\log{R'_{HK}}$ is visible. Relative to the inactive spectra, we find a large number of narrow pseudo-emission features in the active spectra with strengths that are rotationally modulated. These features most likely originate from plage, spots, or a combination of both. They also display radial velocity variations of $\sim$300 m s$^{-1}$ - consistent with an active region rotating across the stellar surface. Furthermore, we see evidence that some of the lines originating from the `active immaculate' photosphere appear broader relative to the `inactive immaculate' case. This may be due to enhanced contributions of e.g. magnetic bright points to these lines, which then causes additional line broadening. More detailed analysis may enable measurements of plage and spot coverage using single spectra in the future.
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