We present new CCD BVI Johnson-Cousins photometry of stars in the fields of the unstudied or poorly studied open clusters Ruprecht 119, NGC 6318 and BH 245, which lie in the constellations of Norma, Scorpius and Sagittarius, respectively, not far from the direction towards the Galactic centre. Since our photometry reached down to V 19 mag, it allowed us for the first time to derive accurate cluster parameters. The present work leads to the following conclusions:
(i) We confirm the physical reality of the three objects as genuine open clusters from different circular extractions in the () and () diagrams and determined their reddening values, distances and ages. The observed cluster areas are not much contaminated by field stars, except that of BH 245 whose CMDs are dominated by two star sequences; the less reddened one corresponding to field stars. BH 245, barely visible in the blue, is the most reddened cluster of the sample (Av 7 mag).
(ii) We derive a ratio E(V-I)/E(B-V)=1.2, which indicates that the interstellar absorption along the line of sight of the clusters approximately follows the normal extinction law.
(iii) Integrated spectra for the cluster sample covering the range from 3500 to 9200 Å yielded independent determinations of cluster parameters. Balmer line equivalent widths and comparisons of the obtained spectra with template spectra provided reddening values and ages for each cluster. The spectroscopic reddening values and ages present very good agreement with the photometric ones. Ruprecht 119, NGC 6318 and BH 245 are very young objects, typically around 10-15 Myr old, which are not dominated by HII region or supergiant phases but by MS stars. Ruprecht 119 might contain some Be stars and/or residual nebular emission as inferred from both integrated spectrum and the presence of star gaps in the () diagram.
(iv) The three studied clusters are located within the solar circle between 1.1 kpc and 3.3 kpc from the Sun. Likewise Westerlund 1 (Piatti et al. 1998c), BH 245 is a highly reddened open cluster located at about 1.0 kpc from the Sun. This high absorption is possibly caused by the presence of individual dark clouds and complexes similar to those optically mapped by Cambrésy (1999).
© European Southern Observatory (ESO) 2000
Online publication: October 30, 2000