@article{HainichRuehlingPasemannetal.2015,
  author    = {Hainich, Rainer and R{\"u}hling, U. and Pasemann, D. and Hamann, Wolf-Rainer},
  title     = {The WN population in the Magellanic Clouds},
  series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  journal   = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87806},
  pages     = {117 -- 120},
  year      = {2015},
  abstract  = {A detailed and comprehensive study of the Wolf-Rayet stars of the nitrogen sequence (WN stars) in the Small Magellanic Cloud (SMC) and the Large Magellanic Cloud (LMC) is presented. We derived the fundamental stellar and wind parameters for more than 100 massive stars, encompassing almost the whole WN population in the Magellanic Clouds (MCs). The observations are fitted with synthetic spectra, using the PotsdamWolf-Rayet model atmosphere code (PoWR). For this purpose, large grids of line-blanket models for different metallicities have been calculated, covering a wide range of stellar temperatures, mass-loss rates, and hydrogen abundances. Our comprehensive sample facilitates statistical studies of the WN properties in the MCs without selection bias. To investigate the impact of the low LMC metallicity and the even lower SMC metallicity, we compare our new results to previous analyses of the Galactic WN population and the late type WN stars from M31. Based on these studies we derived an empirical relation between the WN mass-loss rates and the metallicity. Current stellar evolution tracks, even when accounting for rotationally induced mixing, partly fail to reproduce the observed ranges of luminosities and initial masses.},
  language  = {en}
}
@article{KubatovaHamannTodtetal.2015,
  author    = {Kub{\´a}tov{\´a}, Brankica and Hamann, Wolf-Rainer and Todt, Helge Tobias and Sander, A. and Steinke, M. and Hainich, Rainer and Shenar, Tomer},
  title     = {Macroclumping in WR 136},
  series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  journal   = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87823},
  pages     = {125 -- 128},
  year      = {2015},
  abstract  = {Macroclumping proved to resolve the discordance between different mass-loss rate diagnostics for O-type stars, in particular between Hα and the P v resonance lines. In this paper, we report first results from a corresponding investigation for WR stars. We apply our detailed 3-D Monte Carlo (MC) line formation code to the P v resonance doublet and show, for the Galactic WNL star WR136, that macroclumping is require to bring this line in accordance with the mass-loss rate derived from the emission-line spectrum.},
  language  = {en}
}
@article{SanderHamannHainichetal.2015,
  author    = {Sander, A. and Hamann, Wolf-Rainer and Hainich, Rainer and Shenar, Tomer and Todt, Helge Tobias},
  title     = {Hydrodynamic modeling of massive star atmospheres},
  series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  journal   = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87857},
  pages     = {139 -- 142},
  year      = {2015},
  abstract  = {In the last decades, stellar atmosphere codes have become a key tool in understanding massive stars, including precise calculations of stellar and wind parameters, such as temperature, massloss rate, and terminal wind velocity. Nevertheless, for these models the hydrodynamic equation is not solved in the wind. Motivated by the results of the CAK theory, the models typically use a beta velocity law, which however turns out not to be adequate for stars with very strong winds, and treat the mass-loss rate as a free parameter. In a new branch of the Potsdam Wolf-Rayet model atmosphere (PoWR) code, we solve the hydrodynamic equation consistently throughout the stellar atmosphere. The PoWR code performs the calculation of the radiative force without approximations (e.g. Sobolev). We show the impact of hydrodynamically consistent modelling on OB and WR stars in comparison to conventional models and discuss the obtained velocity fields and their impact on the observed spectral lines.},
  language  = {en}
}