UBVRI CCD photometric study of the open clusters Basel 4 and NGC 7067

Abstract

In this paper we present UBVRI CCD photometry in the region of two young open star clusters Basel 4 and NGC 7067 for the first time. Our sample consists of ~ 4000 stars down to V ~ 21 mag. Stellar surface density profile indicates that radius of Basel 4 and NGC 7067 are about 1.8 and 3.0 arcmin respectively.The (U-B) versus (B-V) diagrams indicate that metallicity of NGC 7067 is solar while that of Basel 4 is Z ~ 0.008. We estimate the mean value of E(B-V) = 0.45$\pm$0.05 and 0.75$\pm$0.05 mag for Basel 4 and NGC 7067 respectively. The analysis of 2MASS JHK data in combination with the optical data in both the clusters yields E(J-K) = 0.30$\pm$0.20 mag and E(V-K) = 1.60$\pm$0.20 mag for Basel 4 while E(J-K) = 0.40$\pm$0.20 mag and E(V-K) = 2.10$\pm$0.20 mag for NGC 7067. Furthermore, colour excess diagrams show a normal interstellar extinction law towards both the clusters. Using the intrinsic colour-magnitude diagrams of the cluster members, we estimated the distances of the clusters as 3.0$\pm$0.2 and 3.6$\pm$0.2 Kpc for Basel 4 and NGC 7067 respectively. By fitting the proper metallicity isochrones to the bright cluster members we estimated the age of the clusters as 200$\pm$50 and 100$\pm$25 Myr for Basel 4 and NGC 7067 respectively. The mass function slope which is derived by applying the corrections of field star contamination and data incompleteness are $1.55\pm0.25$ and $1.68\pm0.47$ for Basel 4 and NGC 7067 respectively. The values of mass function slopes are thus not too different from the Salpeter's (1955) value. Mass segregation is observed in both the clusters which may be due to the dynamical evolutions or imprint of star formation processes or both.