Proper motion analysis to obtain the cluster members. Top left panel: sky distribution of stars within 10 arcmin of the cluster centre. Bottom left panel: vector point diagram with the cluster (coloured dots) and field (grey dots) stars; the green star symbols are the observed stars with FLAMES-UVES, and the insert plots show the density distributions found using GMMs. Right panel: Gaia EDR3 G versus G_BP − G_RP CMD; the green star symbols are the observed stars. From the bottom left and right panels, we can identify that two observed stars have zero membership probability (yellow star symbols).