IPHAS (r^′ − i^′)/(r^′ − Hα) diagram. The solid (red) line is the locus of the main sequence for E(4405 − 5495) = 1 from Drew et al. (2005), while the (magenta) dotted line is the locus of the main sequence for E(4405 − 5495) = 2, roughly defining the envelope for the hot stars that are cluster members. Blue circles are used to indicate the stars selected from Fig. 6 and marked in the same way there. Since all the stars have been selected to have a pseudocolor Q_IR typical of early-type stars or emission-line stars and they all have relatively red (J − K_S) colors, we can safely assume that stars clearly above the main-sequence locus are emission-line stars. Their positions in the 2MASS CMD, (red stars here and in Fig. 6), are in all cases compatible with this interpretation. Both LS III +46 11 and LS III +46 12 are saturated in IPHAS, as all bright O stars in the northern sky are.