@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}
}
@article{HamannKoesterke1998,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {Spectrum formation in clumped stellar winds : consequences for the analyses of Wolf-Rayet spectra},
  year      = {1998},
  language  = {en}
}
@article{HamannKoesterke1998,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {The nitrogen spectra of Wolf-Rayet stars},
  year      = {1998},
  language  = {en}
}
@article{PenaStastinskaEstebanetal.1998,
  author    = {Pena, M. and Stastinska, G. and Esteban, C. and Koesterke, Lars and Medina, S. and Kingsburgh, R.},
  title     = {Galactic planetary nebulae with Wolf-Rayet nuclei : I. Objects with [WC]-early type stars},
  year      = {1998},
  language  = {en}
}
@article{PenaHamannKoesterkeetal.1997,
  author    = {Pena, M. and Hamann, Wolf-Rainer and Koesterke, Lars and Maza, J. and Mendez, R. H. and Peimbert, M. and Ruiz, M. T. and Torres-Peimbert, S.},
  title     = {HST spectrophotometric data of the central star of the planetary nebula LMC-N66},
  year      = {1997},
  language  = {en}
}
@article{KoesterkeHamann1997,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer},
  title     = {Spectral analyses of central of planetary nebulae of early WC-type / NGC 6751 and Sanduleak 3},
  year      = {1997},
  language  = {en}
}
@article{PenaHamannKoesterkeetal.1997,
  author    = {Pena, M. and Hamann, Wolf-Rainer and Koesterke, Lars and Maza, J. and Mendez, R. H. and Peimbert, M. and Ruiz, M. T. and Torres-Peimbert, S.},
  title     = {Spectrophotometric data of the central star of the large magellanic cloud planetary nebula N66. Quantitative analysis of its WN type spectrum},
  year      = {1997},
  language  = {en}
}
@article{KoesterkeHamann1997,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer},
  title     = {Quantitative spectral analyses of CSPNs of early [WC]-type},
  year      = {1997},
  language  = {en}
}
@article{HamannKoesterke1996,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {Spectral analyses with the standard model : Part II: Wolf-Rayet Stars},
  year      = {1996},
  language  = {en}
}
@article{HamannKoesterkeWesselowski1995,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars and Wesselowski, U.},
  title     = {Spectral analyses of the galactic Wolf-Rayet stars : hydrogen-helium abundances and improved stellar parameters for the WN class},
  year      = {1995},
  language  = {en}
}
@article{HamannKoesterkeWesselowski1995,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars and Wesselowski, U.},
  title     = {Spectral atlas of galactic Wolf-Rayet stars (WN-sequence)},
  year      = {1995},
  language  = {en}
}
@article{KoesterkeHamann1995,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer},
  title     = {Spectral analyses of 25 galactic Wolf-Rayet stars of the carbon sequence},
  year      = {1995},
  language  = {en}
}
@article{Koesterke2001,
  author    = {Koesterke, Lars},
  title     = {Spectral analyses of WR-type central stars of Planetary Nebulae},
  year      = {2001},
  abstract  = {So far, the evolution of post-AGB stars is not fully understood. In particular the formation of hydrogen- deficient and hydrogen-free Central Stars of Planetary Nebulae (CSPN) is unsettled. New evolution models, which allow for the consistent treatment of the physics of late thermal pulses, promise new insights to the formation of these stars. In this paper we summarize the results of non-LTE analyses of CSPN with wind. By comparing these results with the predictions of the new evolution models, open questions concerning the evolution of the stars might be answered. In addition we discuss the driving mechanism of the winds of Wolf-Rayet CSPN. New models, which account for millions of iron lines, support the assumptions that these winds are driven by radiation.},
  language  = {en}
}
@article{KoesterkeHamannUrrutia2001,
  author    = {Koesterke, Lars and Hamann, Wolf-Rainer and Urrutia, Tanya},
  title     = {Line-Profile Variability in the Wolf-Rayet Stars WR 135 and WR 111},
  year      = {2001},
  abstract  = {We have obtained time-resolved observations of line-profile variations of the two Wolf-Rayet stars WR 135 and WR 111. The spectra, taken during two consecutive nights, cover a broad range from 4470 to 6590 Ang. The profile variability of the C iii emission line at 5696 Ang in WR 135 is shown in detail. The principal difficulties to constrain the velocity law from the frequency drift of discrete spectral features is discussed, emphasizing the crucial dependence on the adopted location of the line-emission region, and the possible necessity to distinguish between the motion of structures and the flow of the matter. - Full access to the observational data is provided via anonymous file transfer.},
  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{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{HamannKoesterke2000,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {WM stars in the LMC : parameters and atmospheric abundances},
  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{HamannKoesterke1999,
  author    = {Hamann, Wolf-Rainer and Koesterke, Lars},
  title     = {Spectral analyses of Wolf-Rayet stars : the impact of clumping},
  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}
}