Based on imaging and spectroscopy obtained at the ESO NTT telescope and using
an efficient image analysis algorithm, we study the core of the LMC OB
association LH13, particularly the two compact stellar clusters Sk-6641 and HNT
in the HII, region N11C. We resolve Sk-6641 into 15 components and for the
first time the HNT cluster into 70 stars, and derive photometry for the
members. Moreover, from medium resolution spectroscopy we determine the
spectral types for sixteen stars in N11C. We compare the color-magnitude
diagrams of the clusters with that of the field stars and discuss the cluster
ages. With an age of ~100 Myr, the HNT cluster appears significantly older than
the very young (< 5 Myr) Sk-6641 starburst. We suggest that most of the `field'
O-stars in the core of N11C have actually been ejected from Sk-6641 through
dynamical interactions in the compact cluster. The properties of the Sk-6641
and HNT clusters suggest that we are viewing different star formation regions
lying at different distances along the same line of sight.Comment: 12 pages, 8 figure
