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The Disentangled Component Spectra of V578 Mon

The component spectra of the young (2x10^6 yr), eclipsing binary V578 Mon, member of the stellar cluster NGC 2244 in the Rosette Nebula, have been Fourier disentangled and analyzed in detail, using 12 composite spectra (S/N=200) at different orbital phases. Temperatures, rotational velocities and abundances are determined for each component, while the gravity and other fundamental stellar parameters are derived with high precision from analysis of the light-curve and the radial velocities. V578 Mon consists of two massive early-B type components (14.5+10.3 Msun), well inside their critical Roche volume, which move in an eccentric orbit of 2.4 days. The secondary is marginally overluminous in comparison to a single star of its mass and age, while the position of the primary in the HR diagram is fully consistent with the evolutionary tracks for single stars. A search for indications of strong internal mixing in the secondary, e.g. due to motions induced by the proximity of the primary, was negative. No abundance excesses or large velocity fields were found.

eclipsing binary; Fourier disentangling; chemical abundances

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