We report intensive monitoring of the activity variability in the Hα line for 10 Sun-like stars using the 1.88 m reflector at Okayama Branch Office, Subaru Telescope, during the last four years (2019–2022). Our aim was to investigate features of the stellar magnetic activity behavior. We correlated the Hα line variability of each star with the stellar activity levels derived from the Ca ii H&K line, suggesting its efficiency as a magnetic activity indicator. In analyzing the Hα line variation, we observed that some stars exhibited linear or quadratic trends during the observation period. Among several G- and K-type stars expected to have co-existing activity cycles, we confirmed the 2.9 yr short cycle of ϵ Eri (K2V) from the Hα observations. Additionally, we established upper limits on the Hα variability of β Com (G0V) and κ1 Cet (G5V) concerning their expected shorter cycles. We also detected the possibility of short-term activity cycles in two F-type stars, β Vir (F9V; ∼530 d) and α CMi (F5IV-V; ∼130 d). The cycle in α CMi was observed in only one season of our 4 yr observations, suggesting the temporal absence of the cycle period. However, for stars with planets, we did not observe significant magnetic activity variability likely associated with the planetary orbital period. It is speculated that the impact of Hα variability on radial velocity (RV) measurements may vary with spectral type.

中文翻译：

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通过 4 年强化 Hα 线监测发现附近明亮类太阳恒星的磁活动变化

我们报告了过去四年（2019-2022）使用冈山分公司斯巴鲁望远镜的 1.88 m 反射镜对 10 颗类太阳恒星 Hα 线的活动变化进行了密集监测。我们的目的是研究恒星磁活动行为的特征。我们将每颗恒星的 Hα 线变异性与源自 Ca ii H&K 线的恒星活动水平相关联，表明其作为磁活动指标的效率。在分析Hα线变化时，我们观察到一些恒星在观测期间表现出线性或二次趋势。在预计有共存活动周期的几颗 G 型和 K 型恒星中，我们从 Hα 观测中证实了 ϵ Eri (K2V) 的 2.9 年短周期。此外，我们针对 β Com (G0V) 和 κ1 Cet (G5V) 的 Hα 变异性确定了其预期较短周期的上限。我们还检测到两颗 F 型恒星 β Vir（F9V；∼530 d）和 α CMi（F5IV-V；∼130 d）存在短期活动周期的可能性。在我们 4 年的观测中，仅在一个季节观察到了 α CMi 的周期，这表明周期周期暂时不存在。然而，对于有行星的恒星，我们没有观察到可能与行星轨道周期相关的显着磁活动变化。据推测，Hα 变异性对径向速度 (RV) 测量的影响可能因光谱类型而异。