UBVI CCD PHOTOMETRY OF YOUNG OPEN CLUSTERS. II. BOCHUM 7

  • SUNG HWANKYUNG (Department of Earth Science Education, Kyungpook National University, Bohyun-san Optical Astronomy Observatory) ;
  • BESSELL M. S. (Research School of Astronomy & Astrophysics, Australian National University) ;
  • PARK B.-G. (Bohyun-san Optical Astronomy Observatory, Department of Astronomy & Atmospheric Sciences, Kyungpook National University) ;
  • KANG Y. H. (Department of Earth Science Education, Kyungpook National University)
  • Published : 1999.10.01

Abstract

UBVI CCD photometry has been obtained for a region around the Wolf-Rayet star WR 12. We found two young stellar associations in the observed field: the nearer one comprises the field members of Vela OBI association at d = 1.8kpc, while the farther one is the young open cluster Bochum 7 (Bo 7) at d = 4.8kpc. The stars associated with Bo 7 showed no central concentration which suggests that Bo 7 is not a young open cluster but simply a local concentration in the density of young stars belonging to the OB association (Vel OB3). These two associations have similar ages but remarkably different mass function slopes ($\Gamma$ = -2.1 $\pm$ 0.3 for Vel OBI and -1.0 $\pm$ 0.3 for Bo 7). The stars in Vel OBI shows an evident age spread (${\Delta}T\~ 9Myr$). We also found two strong H$\alpha$ emission stars - WR 12 and $\sharp$1066 - from narrow band H$\alpha$ photometry.

Keywords

color-magnitude diagrams (H-R diagram);open clusters and associations: individual (Bo 7);stars: early-type;initial mass function(IMF)

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