Periodic Low-amplitude Radial Velocity Variations in the Supergiant <i>α</i> Persei

Abstract α Per (HD 20902) is one of the brightest F5 supergiants, located at the blue edge of the instability strip. Several studies reported ∼100 day periods in the radial velocity (RV) variations in α Per, but the reported periods and amplitudes were all different, and the origins of these periodic RV variations remained unknown. We obtained 884 spectra for α Per from 2005 to 2020 using the Bohyunsan Observatory Echelle Spectrograph. We found a significant 130.6 day period in RV variations in the generalized Lomb–Scargle periodogram. In addition, the primary 130.6 day period has changed into 66.0 days during the observational duration. The line bisectors, stellar activity indices, such as Ca ii H &amp; K lines and H α equivalent widths, and Hipparcos photometric data were analyzed to establish the origins and the periodicity change of the RV variations. We found ∼130 day periods in line bisector variations, which also changed into ∼66 days as in RV variations, with a time delay of ∼400 days leading the RV variations. Either nonradial oscillations or rotational modulation of surface features can affect both RV and line bisector variations. However, nonradial oscillations are more likely to be the origin of RV variations in α Per, considering the characteristics of the periodogram of RV variations. The change of the periodicities and the time delay between RV and line bisector variations as observed in this work may provide interesting clues to the ongoing physical processes in α Per.