Distributions of stellar ages for low variability stars. The stellar ages are derived from Siess et al. (2000) evolutionary calculations for the reddening laws R_V = 3.1 (top) and R_V = 5.5 (bottom). The open histogram represents the total sample. The yellow area indicates the sample of 608 stars for which we have information about variability from Herbst et al. (2002). The red hatched histogram represents the sources selected with ΔI ≤ 0.4 mag, while the black one corresponds to stars with ΔI ≤ 0.1. The average age of the cluster and the age spread are relative to the third sample.