We present precise radial-velocity (RV) observations of the K-type red supergiant HD 216946 (V424 Lac) obtained over approximately 22 years with the Bohyunsan Optical Astronomy Observatory Echelle Spectrograph (BOES). TheRVmeasurements reveal significant long-period variability with a period of 1,365 days. To investigate its origin, we analyzed the RV data together with line-profile variations (LPVs), chromospheric activity indicators, and published photometric variability. The LPVs exhibit periods of approximately 1,370–1,380 days, while the Na D lines show a similar periodicity near 1,355 days, both comparable to the RV period. In contrast, the H-line indicators display longer periods of 2,730–2,800 days, approximately twice the RV period. The close correspondence between the RV variations and the activity-related diagnostics strongly suggests that the 1,365-day RV signal is primarily linked to chromospheric activity and extended atmospheric variability rather than arising from purely Keplerian motion. Published photometric studies also report additional long-period variability, including a 1,601-day long secondary-period (LSP)-like variation. The coexistence of multiple non-identical periods indicates that the observed variability of HD 216946 is unlikely to originate from a single physical mechanism. We therefore interpret HD 216946 as a multiperiodic red supergiant in which several intrinsic stellar processes coexist. The observed variability is most likely dominated by chromospheric activity and large-scale atmospheric dynamics, possibly accompanied by rotational modulation and LSP-like variability, although the presence of a low-mass stellar companion cannot be completely excluded.

Introduction
Observations and Data Reduction
Stellar Characteristics
Orbital Solution
Observational Diagnostics
    Bisector Behavior
    LPV Characteristics 
    Photometric Variability
    H and Na D Line Behavior
Possible Origins of the RV Variations
    Pulsation
    Rotational Modulation
    Chromospheric Activity
    Companion
    Convection
    Wind Dynamics
Discussion
Acknowledgments
References

• Byeong-Cheol Lee(Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea, Korea University of Science and Technology, Daejeon 34113, Republic of Korea) Corresponding author
• Myeong-Gu Park(Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 41566, Republic of Korea)