The field stars used as astrometric references scatter around the origin of the diagram since they have been selected on the basis of a negligible proper motion. In contrast, most of the Pleiades candidates fall within 3 of the expected cluster's mean motion. The field stars distribution is then . This leads to large distorsions that prevent us from deriving a reliable measurement of its proper motion. Filled dots show VLM and BD candidates and open circles the field stars used as astrometric references.
North is up and East is left.
The cluster proper motion is indicated by a cross and two circles centered on this value are drawn. The membership probability of the candidates is listed in Table 2 . We also list in this table other diagnostics of Pleiades membership obtained by Stauffer et al. However, the long-term proper motion of HHJ 22 has been measured by Hambly et al. We therefore consider this candidate as a cluster member.