Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba, Argentina
2 Instituto de Física, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil
Send offprint request to: A.E. Piatti
Accepted: 23 May 1997
We study the compact open clusters Westerlund 1 (BH 197) and Westerlund 2. We present CCD integrated spectroscopy for both clusters, and CCD imaging in the V and I bands for the former one. So far, Westerlund 1 is possibly the most reddened open cluster studied in detail (). It has an age of 8 ± 3 Myr and a distance from the Sun of kpc. For Westerlund 2 we derive a visual absorption mag, an age of 2-3 Myr, and kpc. From luminosity and structural arguments we conclude that Westerlund 1, although young and compact, it is a massive cluster, in contrast to Westerlund 2.
Key words: open clusters: individual: Westerlund 1, Westerlund 2 / open clusters: general
Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the Universities of La Plata, Córdoba and San Juan, Argentina, and at the University of Toronto (David Dunlap Observatory) 24-inch telescope, Las Campanas, Chile.
The photometric observations are available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsweb.u-strasbg.fr/Abstract.html
© European Southern Observatory (ESO), 1998