CONICET | Buscador de Institutos y Recursos Humanos

Aims. Determine accurate distances and ages of eight open clusters in order to: (1) assess their possible binarity (2) provide probes for tracing the structure of the Third Galactic Quadrant.Determine accurate distances and ages of eight open clusters in order to: (1) assess their possible binarity (2) provide probes for tracing the structure of the Third Galactic Quadrant. Methods. Cluster reddenings, distances, ages and metallicities are derived from ZAMS and isochrone fits in UBVRI photometric diagrams. Field contamination is reduced by restricting analysis to stars within the cluster limits derived from star counts. Further membership control is done by requiring that stars have consistent positions on several diagrams and by using published spectral types. Results. The derived distances, ages and metallicities have shown that none of the analysed clusters compose binary/double systems. Of the four candidate pairs, only NGC 2383/NGC 2384 are close to each other, but have dierent metallicities and ages. Ruprecht 72 and Ruprecht 158 are not clusters but fluctuations of the field stellar density. Ha ner 18 is found to be superposition of two stellar groups at different distances: Haner 18(1) at 4.5 kpc and Ha ner 18(2) between 9.5 and 11.4 kpc from the Sun. The derived distances and ages have been used for situating the clusters in a Galactic context. In particular, young stellar groups are tracing spiral structure at large Galactocentric radii. At least two clusters formed during the last few 108 yr in an interstellar medium with less than solar abundances.The derived distances, ages and metallicities have shown that none of the analysed clusters compose binary/double systems. Of the four candidate pairs, only NGC 2383/NGC 2384 are close to each other, but have dierent metallicities and ages. Ruprecht 72 and Ruprecht 158 are not clusters but fluctuations of the field stellar density. Ha ner 18 is found to be superposition of two stellar groups at different distances: Haner 18(1) at 4.5 kpc and Ha ner 18(2) between 9.5 and 11.4 kpc from the Sun. The derived distances and ages have been used for situating the clusters in a Galactic context. In particular, young stellar groups are tracing spiral structure at large Galactocentric radii. At least two clusters formed during the last few 108 yr in an interstellar medium with less than solar abundances. Conclusions. In contrast with the LMC, double clusters are apparently rare, or even non existent, in the tranquil environment of the Third Galactic Quadrant. This leaves the open the question of whether binary clusters form more easily toward denser and more violent regions of the Milky Way such as the inner Galaxy.In contrast with the LMC, double clusters are apparently rare, or even non existent, in the tranquil environment of the Third Galactic Quadrant. This leaves the open the question of whether binary clusters form more easily toward denser and more violent regions of the Milky Way such as the inner Galaxy.