Context. Spectroscopic investigations of galactic open clusters are scarce and limited to a reduced sample of cluster members.
Aims: We intend to perform a complete study of the physical parameters of two galactic clusters as well as of their individual members.
Methods: To carry out this study, we used the BCD (Barbier-Chalonge-Divan) spectrophotometric system, which is based on the study of the Balmer discontinuity and is independent of interstellar and circumstellar extinction. Additional physical properties were derived from the line profiles (FWHM) and stellar evolution models. We analyzed low-resolution spectra around the Balmer discontinuity for normal B-type and Be stars in two open clusters:
Results: The cluster parameters obtained through the BCD method agree very well with those derived from classical methods based on photometric data. The BCD system also provides physical properties of the star members. This study enables us to test the good behavior of Mbol(λ1,D)-calibrations and detect systematic discrepancies between log g estimates from model atmospheres and those derived from stellar evolution models. To improve our knowledge on the formation and evolution of the clusters, more statistical studies on the initial mass luminosity and angular momentum distributions should be addressed. Therefore, the BCD spectrophotometric system could be a powerful tool for studying far galactic and extragalactic clusters with the generation of large telescopes and the multi-object technique.
Astronomy and Astrophysics
- Pub Date:
- August 2012
- open clusters and associations: individual: NGC 3766;
- stars: emission-line;
- stars: fundamental parameters;
- open clusters and associations: individual: NGC 4755;
- stars: early-type