Top: zoom-in on the region of the colour-period diagram in which the bifurcation of the slow rotator sequence is observed. The longer-period sequence (S-slow rotators) is shown in orange and the shorter-period sequence (F-slow rotators) in blue. Additional slow rotators outside the region of interest are marked in black, and fast rotators in green. Squares indicate binaries. Bottom: corresponding colour-magnitude diagram (same symbols as above) with additional cluster members without determined rotation periods marked with open symbols. The equal-mass binary sequence is almost exclusively populated by the F-slow rotators, indicating a connection between faster rotation and binarity.