Star clusterings in the Carina complex: UBVRI photometry of Bochum 9, 10 and 11

Abstract

We report on the first UBVRI CCD photometry of three poorly known star clusterings in the region of Eta Carinae: Bochum9, Bochum10 and Bochum11. We found that they are young, rather poor and loose open clusters. We argue that Bochum9 is probably a small and loose cluster with about 30 probable members having E(B-V)=0.63, located 4.6 kpc far from the Sun, beyond the Carina spiral arm. Similarly, Bochum10 is a sparse aggregate with 14 probable members having E(B-V)=0.47 and at a distance of 2.7 kpc from the Sun. Finally, Bochum11 is a less than 4x10^6 yrs old cluster for which we identify 24 members. It has a reddening E(B-V)=0.58, and lies between Bochum10 and 9, at 3.5 kpc from the Sun. We propose that in the field of the cluster some stars might be pre Main Sequence (MS) candidates.