r − i, r − Hα CMD showing all the sources in the field (grey dots), along with their mean colours and corresponding standard deviations (blue). The red-scale points show the colours of stars with measured pEWs from spectroscopy, coloured by its value. The sources above the black dashed line are selected as potential member candidates due to an enhanced Hα emission. This selection is further refined using the proper motions and position in CMDs.