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Multicolor CCD Photometry and Stellar Evolutionary Analysis of NGC 1907, NGC 1912, NGC 2383, NGC 2384, and NGC 6709 Using Synthetic Color-Magnitude Diagrams
We present the first CCD photometric observations of NGC 2383 and NGC2384 in B, V, R, and I, NGC 1912, NGC 6709 in B, V, and I and NGC 1907in B and V passbands, reaching down to a limiting magnitude of V~20 magfor ~3300 stars put together. The results of the spectroscopicobservations of 43 bright stars in the field of NGC 1912, NGC 2383, NGC2384, and NGC 6709 are also presented. The color-magnitude diagrams(CMDs) of the clusters in V versus B-V, V versus V-R, and V versus V-Iare presented. The distances and reddening to these clusters aredetermined using the cluster CMDs. The distances to the clusters NGC1907, NGC 1912, NGC 2383, NGC 2384, and NGC 6709 are 1785+/-260,1820+/-265, 3340+/-490, 2925+/-430, and 1190+/-175 pc, respectively.Some gaps in the cluster main sequence have been identified. We havecompared the observed color-magnitude diagrams of these four openclusters with the synthetic ones derived from one classical and twoovershoot stellar evolutionary models. Overshoot models estimate olderages for clusters when compared to the classical models. The age of theclusters estimated using the isochrones of Bertelli et al. are 400, 250,400, 20, and 315 Myr for the clusters NGC 1907, NGC 1912, NGC 2383, NGC2384, and NGC 6709, respectively. A comparison of the syntheticcolor-magnitude diagrams with the observed ones indicates that theovershoot models should be preferred. The comparison of integratedluminosity functions do not clearly indicate as to which model is to bepreferred. The values of the mass function slopes estimated for theclusters are x=1.7+/-0.15 for NGC 1912 (mass range: 1.7-3.9 M_solar) andNGC 6709 (1.7-3.4 M_solar), x=1.3+/-0.15 for NGC 2383 (1.7-3.1 M_solar),and x=1.0+/-0.15 for NGC 2384 (2.0-14.0). The present age estimates showthat the closely located cluster pair NGC 1912 + NGC 1907 have similarages, indicating that they may have born together, making them a goodcandidate to be a binary open cluster.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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