Physical parameters of pre-main sequence stars in open clusters

Received; accepted Context. The search and analysis of pre-main sequence (PMS) stars in Galactic young open clusters (YOCs) Aims. The aims are twofold: To determine the ages, masses and spatial distribution of PMS members in young open clusters, and to check and compare the performances of different model isochrones Methods. We compare UBVRI photometric observations to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for both main sequence (MS) and PMS stars, and estimates for the physical prop-erties of the cluster candidate members: masses, ages, and spatial distribution inside the cluster Results. The photometric measurement of an average (U − V) excess, considered as an indication of the presence of accretion disks, is considered prior to membership assignment. This photometric excess is correlated with cluster age, suggesting a vanishing of disks, able to show up in (U − V) excess, at ages around 5 Myr. We find more satisfactory values of measured masses from comparison to models in the colour-magnitude (CM) diagram than in the theoretical HR plane. The obtained cluster mass functions show a marginal steepening with cluster age. Significant variations in the mass function slopes are found with the models used in member selection. The clusters NGC 3293 and NGC 2362 are found to have mass functions flatter than the Salpeter slope for all models considered. The relation between the calculated dispersion of PMS age and the characteristic clustering scale of the cluster shows an interestin