@article{OskinovaGayleyHamannetal.2012,
  author    = {Oskinova, Lida and Gayley, K. G. and Hamann, Wolf-Rainer and Huenemoerder, D. P. and Ignace, R. and Pollock, A. M. T.},
  title     = {HIGH-RESOLUTION X-RAY SPECTROSCOPY REVEALS THE SPECIAL NATURE OF WOLF-RAYET STAR WINDS},
  series = {ASTROPHYSICAL JOURNAL LETTERS},
  volume    = {747},
  journal   = {ASTROPHYSICAL JOURNAL LETTERS},
  number    = {2},
  publisher = {IOP PUBLISHING LTD},
  address   = {BRISTOL},
  issn      = {2041-8205},
  doi       = {10.1088/2041-8205/747/2/L25},
  pages     = {6},
  year      = {2012},
  abstract  = {We present the first high-resolutionX-ray spectrum of a putatively singleWolf-Rayet (WR) star. 400 ks observations of WR 6 by the XMM-Newton telescope resulted in a superb quality high-resolution X-ray spectrum. Spectral analysis reveals that the X-rays originate far out in the stellar wind, more than 30 stellar radii from the photosphere, and thus outside the wind acceleration zone where the line-driving instability (LDI) could create shocks. The X-ray emitting plasma reaches temperatures up to 50 MK and is embedded within the unshocked, "cool" stellar wind as revealed by characteristic spectral signatures. We detect a fluorescent Fe line at approximate to 6.4 keV. The presence of fluorescence is consistent with a two-component medium, where the cool wind is permeated with the hot X-ray emitting plasma. The wind must have a very porous structure to allow the observed amount of X-rays to escape. We find that neither the LDI nor any alternative binary scenario can explain the data. We suggest a scenario where X-rays are produced when the fast wind rams into slow "sticky clumps" that resist acceleration. Our new data show that the X-rays in single WR star are generated by some special mechanism different from the one operating in the O-star winds.},
  language  = {en}
}