TY  - JOUR
A1  - Gräfener, Götz
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
T1  - The impact of iron group elements on the ionizatin structure of WC star atmospheres : WR111
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
A1  - Gräfener, Götz
T1  - Non-LTE models of WR winds
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
T1  - WM stars in the LMC : parameters and atmospheric abundances
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Hamann, Wolf-Rainer
A1  - Koesterke, Lars
T1  - WN stars in the LMC : parameters and atmospheric abundances
N2  - The spectra of 18 WN stars in the Large Magellanic Cloud (LMC) are quantitatively analyzed by means of "standard" Wolf-Rayet model atmospheres, using the helium and nitrogen lines as well as the spectral energy distribution. The hydrogen abundance is also determined. Carbon is included for a subset of 4 stars. The studied sample covers all spectral subtypes (WN2 ... WN9) and also includes one WN/WC transition object. The luminosities of the program stars span a wide range ( L/Lsun = 5.0 ... 6.5). Due to the given LMC membership, these results are free from uncertainties inferred from the distance. 50 % of the studied stars (both, late and early WN subtypes) have rather low luminosity (L/Lsun < 5.5). This puts tough constraints on their evolutionary formation. If coming from single stars, it provides evidence for strong internal mixing processes. The empirical mass-loss rates are scaled down by a factor of about two due to the impact of clumping, compared to previous studies adopting homogeneous winds. There is no obvious strong correlation between the mass-loss rates and other parameters like luminosity, temperature and composition. The stellar parameters for the present LMC sample are not systematically different from those of the Galactic WN stars studied previously with the same techniques, in contrast to the expected metallicity effects.
Y1  - 2000
ER  -