Compact star clusters of the LMC HII region N11C

Based on imaging and spectroscopy obtained at the ESO NTT telescope and usi ng an efficient image analysis algorithm, we study the core of the LMC OB a ssociation LH 13, particularly the two compact stellar clusters Sk-66 degre es 41 and HNT in the H II region N 11C. We resolve Sk-66 degrees 41 into 15 components and for the first time the HNT cluster into 70 stars, and deriv e photometry for the members. Moreover, from medium resolution spectroscopy we determine the spectral types for sixteen stars in N 11C. We compare the color-magnitude diagrams of the clusters with that of the field stars and discuss the cluster ages. With an age of similar to 100 Myr, the HNT cluste r appears significantly older than the very young (less than or equal to 5 Myr) Sk-66 degrees 41 starburst. We suggest that most of the 'field' O-star s in the core of N 11C have actually been ejected from Sk-66 degrees 41 thr ough dynamical interactions in the compact cluster. The properties of the S k-66 degrees 41 and HNT clusters suggest that we are viewing different star formation regions lying at different distances along the same line of sigh t.