2460 20160701171705.0 ASTROimport-617 Pavlovski, K. 2001 Chemical Composition of V578 Mon - An Eclipsing Binary in the Rosette Nebula Cluster NGC 2244 The fortunate circumstance that the double-lined eclipsing binary V578 Mon is member of the young open cluster NGC 2244, situated in the central hole of the Rosette Nebula, allows to derive the physical properties and evolutionary status of its components as well as the age of and the distance to the cluster and the nebula. A new approach, using Fourier disentangling to separate the composite binary spectra into individual component spectra (c.f. Hensberge, Pavlovski Verschueren 2000, A 358, 553) leads to high precision results. The disentangled spectra can thereafter be analyzed as if it were single star spectra. The present contribution is the continuation of our work on V578 Mon and concentrates on the derivation of preliminary abundances for both components. The rotational velocities are about 100 and 120 km s-1; hence, abundances are derived differentially to the template spectrum of the sharp-lined cluster star NGC2244-#201. Abundances for #201 and another two B1 stars were previously derived (Vrancken et al. 1997, A 320, 878). Now, we have chemical abundances for five early-B stars in the range of the effective temperatures from 26 000 - 30 000 K. These stars have projected rotational velocties ranging from 22 to 260 km s-1. All these stars have the same atmospheric chemical composition in He and CNO elements within an rms accuracy of about 0.05 dex. Hensberge, H. Ilijic, S. Astronomische Gesellschaft Meeting Abstracts 18 2001 http://esoads.eso.org/abs/2001AGM....18..P71P published in NONREF