A STRICT TEST OF STELLAR EVOLUTION MODELS: THE ABSOLUTE DIMENSIONS OF THE MASSIVE BENCHMARK ECLIPSING BINARY V578 MON

We determine the absolute dimensions of the eclipsing binary V578 Mon, a detached system of two early B-type stars (B0V + B1V, P = 2.40848 days) in the star-forming region NGC 2244 of the Rosette Nebula. We find that our disentangled component spectra for V578 Mon agree well with previous spectral disentangling from the literature. We compare the absolute dimensions to the rotating models of the Geneva and Utrecht groups and the models of the Granada group. We find that all three sets of models marginally reproduce the absolute dimensions of both stars with a common age within the uncertainty for gravity-effective temperature isochrones. However, there are some apparent age discrepancies for the corresponding mass-radius isochrones. We find the relativistic contribution to the apsidal motion to be small,