Distribution of stars with assigned cluster membership, on the RA–Dec plane. With small grey filled circles we indicate all observed stars, with large blue filled circles the GIRAFFE radial velocity members, with red filled squares the UVES radial velocity members, with a green filled triangle the possible binary star discussed in the text and with a black cross we indicate the location of the cluster centre (as determined in Sect. 6). With open grey circles we indicate stars with RVs consistent with cluster membership, although their proper motions lie outside the 3-σ acceptance radius discussed in Sect. 4.1 and shown in Fig. 2