Abstract

We report the results of a study of spot activity manifestations in 11 K-type dwarfs with established planets in the habitable zone according to the data from the Kepler space telescope archive acquired during 90-day long Q3-set observations. We found that the spot area \(A\) on the surface of K-type dwarfs of our list is greater than the characteristic solar value, but is comparable to the maximum levels observed for the Sun, except for the active star KIC 9351316 with \(A=7588\) MSH. We performed a detailed study of the K-type dwarf KIC 5938970 (Kepler-1540) with flare activity higher than that of the Sun and flare energy \(\log E\) spanning the 32.95–34.48 interval. We estimated the rotation period of the star, \(P=15\overset{\textrm{d}}{.}1447\), and its parameter \(\Delta\Omega=0.024\pm 0.007\) rad/day. Based on the Kamogata Wide-field Survey data (99 \(V\)-band magnitude estimates in 3310 days) we conclude that photometric variations include cyclic changes and a weak monotonic brightness increase. The characteristic periods of possible cycles are equal to 2.8 and 4.4 years. Our study of the star’s activity in about half of the currently known K-type dwarfs with planets in the habitable zone (11 objects among 17 stars in the complete list) based on high-precision observations made with the Kepler telescope revealed certain activity manifestations (high flare activity in one star, high spot activity in another, etc.). We conclude that a detailed study of activity manifestations in each particular star is highly desirable when studying planetary systems of K-type stars including planets in the habitable zone.

中文翻译：

---

11颗位于宜居带行星的K型矮星的活动分析

摘要

我们根据开普勒太空望远镜档案在为期 90 天的 Q3 组观测中获得的数据，报告了对 11 个在宜居带内已建立行星的 K 型矮星的点活动表现的研究结果。我们发现，我们列表中的 K 型矮星表面的光斑面积\(A\)大于太阳特征值，但与观测到的太阳最大水平相当，但活跃恒星 KIC 9351316 除外\(A=7588\) MSH。我们对 K 型矮星 KIC 5938970 (Kepler-1540) 进行了详细研究，其耀斑活动高于太阳，耀斑能量 \ (\log E\)跨越 32.95–34.48 区间。我们估算了恒星的自转周期，\(P=15\overset{\textrm{d}}{.}1447\)，及其参数\(\Delta\Omega=0.024\pm 0.007\) rad/day。基于鸭方广域调查数据（99 \(V\)- 3310 天的波段星等估计）我们得出结论，光度变化包括循环变化和微弱的单调亮度增加。可能周期的特征周期等于2.8年和4.4年。我们基于开普勒望远镜的高精度观测，对目前已知的大约一半行星位于宜居带的 K 型矮星（完整列表中 17 颗恒星中的 11 个天体）的恒星活动进行了研究，揭示了某些活动表现（一颗恒星的耀斑活动较高，另一颗恒星的斑点活动较高，等等）。我们的结论是，在研究 K 型恒星的行星系统（包括宜居带中的行星）时，非常需要对每颗特定恒星的活动表现进行详细研究。