CMDs in various color systems (upper panels a–c) for the 32 periodic Ru147 cluster members. Bottom panel d: corresponding color-period diagram (CPD) for the same stars. The 3 F-type stars past the cluster turnoff are marked with red symbols, single main sequence cluster members are in green, and yellow symbols indicate known binaries. The plot symbols encode both object type and period category (large symbols for Cat. 1 periods, small for Cat. 2) as indicated in the legend. The sun is marked with its usual symbol in both the CMD and CPD and is displayed only as a reference point. The encircled star is EPIC 219333882, for which multiples of our period are equally plausible (see text).