@article{KoesterkeHamannGraefener1999,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer and Gr{\"a}fener, G{\"o}tz},
  title     = {Inhomogeneities in Wolf-Rayet atmospheres},
  year      = {1999},
  language  = {en}
}
@article{GraefenerHamannKoesterke1999,
  author    = {Gr{\"a}fener, G{\"o}tz and Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {Spectral analyses of WC stars in the LMC},
  year      = {1999},
  language  = {en}
}
@article{HamannKoesterkeGraefener1999,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars and Gr{\"a}fener, G{\"o}tz},
  title     = {Modelling and quantitative analyses of WR spectra : recent progress and results},
  year      = {1999},
  language  = {en}
}
@article{DeMarcoSchmutzKoesterkeetal.1999,
  author    = {DeMarco, O. and Schmutz, W. and Koesterke, Lars and Hamann, Wolf-Rainer and DeMarco, O. and DeKoter, A.},
  title     = {Why should we compare WR codes?},
  year      = {1999},
  language  = {en}
}
@article{DeMarcoSchmutzKoesterkeetal.1999,
  author    = {DeMarco, O. and Schmutz, W. and Koesterke, Lars and Hamann, Wolf-Rainer},
  title     = {Gamma 2 Velorum revisited},
  year      = {1999},
  language  = {en}
}
@article{GraefenerHamannKoesterke2000,
  author    = {Gr{\"a}fener, G{\"o}tz and Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {The impact of iron group elements on the ionizatin structure of WC star atmospheres : WR111},
  year      = {2000},
  language  = {en}
}
@article{HamannKoesterkeGraefener2000,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars and Gr{\"a}fener, G{\"o}tz},
  title     = {Non-LTE models of WR winds},
  year      = {2000},
  language  = {en}
}
@article{HamannKoesterke2000,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {WM stars in the LMC : parameters and atmospheric abundances},
  year      = {2000},
  language  = {en}
}
@article{HamannKoesterke2000,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {WN stars in the LMC : parameters and atmospheric abundances},
  year      = {2000},
  abstract  = {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.},
  language  = {en}
}
@article{HamannBrownFeldmeieretal.2001,
  author    = {Hamann, Wolf-Rainer and Brown, John C. and Feldmeier, Achim and Oskinova, Lidia M.},
  title     = {On the wavelength drift of spectral features from structured hot star winds},
  year      = {2001},
  abstract  = {Spectral lines formed in stellar winds from OB stars are observed to exhibit profile variations. Discrete Absorption Components (DACs) show a remarkably slow wavelength drift with time. In a straightforward interpretation, this is in sharp contradiction to the steep velocity law predicted by the radiation-driven wind theory, and by semi- empirical profile fitting. In the present paper we re-discuss the interpretation of the drift rate. We show that the Co- rotating Interaction Region (CIR) model for the formation of DACs does not explain their slow drift rate as a consequence of rotation. On the contrary, the apparent acceleration of a spectral CIR feature is even higher than for the corresponding kinematical model without rotation. However, the observations can be understood by distinguishing between the velocity field of the matter flow, and the velocity law for the motion of the patterns in which the DAC features are formed. If the latter propagate upstream against the matter flow, the resulting wavelength drift mimics a much slower acceleration although the matter is moving fast. Additional to the DACs, a second type of recurrent structures is present in observed OB star spectra, the so-called modulations. In contrast to the DACs, these structures show a steep acceleration compatible with the theoretically predicted velocity law. We see only two possible consistent scenarios. Either, the wind is accelerated fast, and the modulations are formed in advected structures, while the DACs come from structures which are propagating upstream. Or, alternatively, steep and shallow velocity laws may co-exist at the same time in different spatial regions or directions of the wind.},
  language  = {en}
}