Fraction of stars with detected periods. Panel a: spatial distribution of the cluster stars, color coded to indicate both coverage in K2, and whether a periodic signal was identified (green) or not (red). Panel b: histogram of the stars identified as Ru147 members and its coverage in K2. Gray depicts all stars identified as Ru147 members in Sect. 2.2. Stars for which we found periodic signals are displayed in green, while red symbols indicate the remaining stars observed by Kepler/K2.