BY Draconis Stars in Two Galactic Clusters: Exploring the Rotation and Cyclical Variability of the Brighter Members

This study examines the rotational and cyclic variability of 79 BY Draconis stars in the M45 (Pleiades) and Alpha Persei clusters, refining their rotation and activity cycle periods through Lomb-Scargle periodogram analysis. Photometric data from ASAS-SN, supplemented by observations from multiple observatories, reveal significant differences in period distributions between the clusters, highlighting the influence of stellar age on rotational and magnetic activity cycles. Key findings include a moderate positive correlation between cyclic amplitude (AMP-C) and cyclic period (PCYC), suggesting that stronger magnetic fields require longer timescales for full activity cycles. A strong correlation between rotational amplitude (AMP-R) and cyclic amplitude (AMP-C) supports the link between short-term rotational modulation and long-term stellar magnetic cycles. However, the weak correlation between rotation period (PROT) and cyclic period (PCYC) indicates that additional factors beyond rotation influence cyclic variability. These results contribute an updated dataset of rotational and cyclic periods for BY Draconis stars, reinforcing the importance of long-term monitoring to better understand stellar magnetic evolution and dynamo-driven activity cycles.