M_V/ (B − V)₀ diagram for selected likely members. Red squares represent red and yellow supergiants spectroscopically observed in the field. The solid line is the isochrone of Marigo et al. (2008) corresponding to log t = 7.20, unreddened and displaced to DM = 13.8. The dashed line is the isochrone of Marigo et al. (2008) corresponding to log t = 7.08, unreddened and displaced to DM = 14.5. The value used for R is the standard value of 3.1.