@article{GraefenerHamannHillieretal.1998,
  author    = {Gr{\"a}fener, G{\"o}tz and Hamann, Wolf-Rainer and Hillier, D. J. and Koesterke, Lars},
  title     = {Spectral analyses of WC stars in the LMC},
  year      = {1998},
  language  = {en}
}
@phdthesis{Graefener1999,
  author    = {Gr{\"a}fener, G{\"o}tz},
  title     = {Spektralanalysen von WC-Sternen in der LMC},
  pages     = {93 S. : graph. Darst.},
  year      = {1999},
  language  = {de}
}
@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{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{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{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{HamannKoesterkeGraefener2002,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars and Gr{\"a}fener, G{\"o}tz},
  title     = {Spectral analyses of Wolf-Rayet winds},
  year      = {2002},
  abstract  = {The analysis of Wolf-Rayet spectra requires adequate model atmospheres which treat the non-LTE radiation transfer in a spherically expanding medium. Present state-of-the-art calculations account for complex model atoms with, typically, a few hundred energy levels and a few thousand spectral lines of He and CNO elements. In the most recent version of our model code, blanketing by millions of lines from iron-group elements is also included. These models have been widely applied for the spectral analysis of WN stars in the Galaxy and LMC. WN spectra can be well reproduced in most cases. WC stars have not yet been analyzed comprehensively, because the agreement with observations becomes satisfactory only when line-blanketed models are applied. The introduction of inhomogeneities (clumping), although treated in a rough approximation, has significantly improved the fit between synthetic and observed spectra with respect to the electron-scattering wings of strong lines. The mass-loss rates obtained from spectral analyses become smaller by a factor 2-3 if clumping is accounted for. A pre-specified velocity law is adopted for our models, but the radiation pressure can be evaluated from our detailed calculation and can be compared a posteriori with the required wind acceleration. Surprisingly we find that the line-blanketed models are not far from being hydrodynamically consistent, thus indicating that radiation pressure is probably the main driving force for the mass-loss from WR stars.},
  language  = {en}
}
@article{GraefenerKoesterkeHamann2002,
  author    = {Gr{\"a}fener, G{\"o}tz and Koesterke, Lars and Hamann, Wolf-Rainer},
  title     = {Line-blanketed model atmospheres for WR star},
  year      = {2002},
  abstract  = {We describe the treatment of iron group line-blanketing in non-LTE model atmospheres for WR stars. As an example, a blanketed model for the early-type WC star WR 111 is compared to its un-blanketed counterpart. Blanketing affects the ionization structure and the emergent flux distribution of our models. The radiation pressure, as computed within our models, falls short by only a factor of two to provide the mechanical power of the WR wind.},
  language  = {en}
}
@article{KoesterkeHamannGraefener2002,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer and Gr{\"a}fener, G{\"o}tz},
  title     = {Expanding atmospheres in non-LTE : Radiation transfer using short characteristics},
  year      = {2002},
  abstract  = {We present our technique for solving the equations of radiation transfer in spherically expanding atmospheres. To ensure an efficient treatment of the Thomson scattering, the mean intensity J is derived by solving the moment equations in turn with the angle-dependent transfer equation. The latter provide the Eddington factors. Two different methods for the solution of the angle dependent equation are compared. Thereby the integration along short characteristics turned out to be superior in our context over the classical differencing scheme. The method is the basis of a non-LTE code suitable for the atmospheres of hot stars with high mass-loss.},
  language  = {en}
}