Estudio fotométrico y espectroscópico CCD de los cúmulos abiertos moderadamente jóvenes NGC 5999, NGC 6031, Ruprecht 115 y Ruprecht 120

PIATTI, ANDRÉS E.; CLARIA OLMEDO, JUAN JOSÉ; BICA, EDUARDO

La Plata

Congreso; Reunión Anual de la Asoc. Argentina de Astronomía; 1998

We present CCD BVI Jonhson-Cousins photometry for the southern open clusters NGC 5999, NGC 6031, Ruprecht 115 and Ruprecht 120. The sample consists of about 1160 stars reaching down to V~19 mag. From the analysis of the colour-magnitud diagrams, we confirm the reality of the clusters and derived their fundamental parameters (reddening, distance and age). We also present integrated spectra for NGC 6031, Ruprecht 115 and Ruprecht 120 covering a range from 3500 to 9200 Å. >From the equivalent widths of Balmer and infrared CaII triplet lines as well as from the comparison of the obtained spectra with those of template clusters, we derived reddening, age and metallicity. The photometric and spectroscopic results allow us to conclude that the four clusters are moderately young (age ~ 100-500 Myr) and are located approximately towards the Galactic centre at ~ 2.3 kpc from the Sun. NGC 6031 and Ruprecht 120 have nearly solar metal content, while Ruprecht 115 appears to be slightly metal-rich.