Vol 21, No 6

Stellar activity cycles as revealed by long-term beat-like patterns from light curves of Kepler

Heng-Geng Han, Kai-Ming Cui, Ji-Feng Liu, Hui-Qin Yang, Xuan Fang, Rui-Ning Zhao


Abstract Stellar activity cycles have been found on many stars through different methods. Although in debate, an empirical relation has been found where a period of stellar activity cycle Pcyc is positively correlated with rotation period Prot along some segregated branches. In this work, we built a systematic process to search for the Kepler objects that are analogous to the long-term solar brightness variations and investigate their possible origins. After a rigorous selection, we obtained 43 objects that all exhibit clear long-term beat-like patterns and their variability (amplitude of rotational modulation) periods and rotation periods were derived. Due to the 4-year duration of the Kepler mission, our targets are located in the region where the cycle periods are longer than ∼1 yr and shorter than ∼2.5 yr. However, all of our targets exhibit clear and notable quasi-periodic variations in variability, yet we cannot confirm any linear trends that were predicted by previous research independently. This may suggest that in the Kepler realm of the Pcyc – Prot diagram, these relations would mix with each other or the beat-like patterns may not be related to the stellar cycle unless other evidence is provided.


Keywords stars: activity — starspots — stars: rotation

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