The positions of the stars studied for cluster membership in the colour-magnitude diagram. Different symbols indicate stars with different membership probabilities: squares represent stars with cluster membership probability higher than 60%, circles stars with a probability between 14% and 60%, and triangles membership probability between 1% and 14%. Non-members and runaway stars are marked by dots and crosses, respectively. One runaway star, HD 171589, does not appear in this figure, as its colour and magnitude do not fit the presented parameter space (see Table 4). The three stars with magnetic fields, HD 155806, HD 156154, and HD 164794, with high cluster membership probabilities are denoted by filled squares. Isochrones for log t = 6.6, 6.8, 7.0, and 7.2 are presented by solid lines and the zero-age main sequence is shown as a dashed line.