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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