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 (Γ = -2.1 ± 0.3 for Vel OBI and -1.0 ± 0.3 for Bo 7). The stars in Vel OBI shows an evident age spread (ΔT~ 9Myr). We also found two strong Hα emission stars - WR 12 and #1066 - from narrow band Hα photometry.

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