THE YOUNG OPEN CLUSTER MARKARIAN 50

G. BAUME; R.A. VÁZQUEZ; G. CARRARO

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2004 vol. 355 p. 475 - 484

0035-8711

We report on a deep CCD UBV(RI)C photometric survey in the region of the young open cluster Markarian 50. The new photometric data allow us to extend the cluster membership down to V~ 17.5, about 2 mag deeper than any previous investigation. On the basis of these data we derive a distance d= 3460 +/- 350 pc (VO-MV= 12.7 +/- 0.2), which turns out to be only slightly lower than previous estimates. The cluster presents differential reddening, with E(B-V) values ranging from 0.69 to 1.1. The brightest member (HD 219460) is a double star, which we separate photometrically for the first time, providing individual magnitudes and colours for each component. One of them is a Wolf-Rayet (WR) star and, according to evolutionary models, the mass of its progenitor should be greater than ~20 Msolar. The age obtained for the cluster is 7.5 +/- 2 Myr and the mass function for the most massive stars (M > 1 Msolar) presents a slope x~ 1.0.