UBV I CCD photometry of the open clusters NGC 4609 and Hogg 15

Abstract

UBV I CCD photometry is obtained for the open clusters NGC 4609 and Hogg 15 in Crux. For NGC 4609, CCD data are presented for the first time. From new photometry we derive the reddening, distance modulus and age of each cluster - NGC 4609: E(B - V) = 0.37 ± 0.03, V0-MV = 10.60 ± 0.08, log Γ = 7.7 ± 0.1; Hogg 15: E(B - V) = 1.13 ± 0.11, V0-MV = 12.50 ± 0.15, log Γ ≲ 6.6. The young age of Hogg 15 strongly implies that WR 47 is a member of the cluster. We also determine the mass function of these clusters and obtain a slope Γ = -1:2 (±0:3) for NGC 4609 which is normal and a somewhat shallow slope (Γ = -0:95 ± 0:5) for Hogg 15. © 2010 The Korean Astronomical Society.