The Galactic WN stars: line-blanketed analyses versus evolutionary models
W.-R. Hamann, G. Gräfener and A. Liermann
An almost complete sample of Galactic WN stars has been analyzed by means of the Potsdam Wolf-Rayet (PoWR) model atmospheres, which account for iron line blanketing and clumping. We obtain a homogeneous set of stellar parameters, partly revising earlier results. The Galactic WN population is compared with a synthetic population, generated from the Geneva tracks for massive star evolution. With the new Geneva models which account for rotationally induced mixing, the discrepancy between the synthetic and observed population is less dramatic than with the older tracks without rotation. Nevertheless, the observed bimodal distribution between WN-late stars of high luminosity and hydrogen-free WN-early stars of lower luminosity is not reproduced by the evolutionary models. We conclude that the evolution of massive stars is still not understood satisfactory.
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