HIGH-RESOLUTION X-RAY SPECTROSCOPY REVEALS THE SPECIAL NATURE OF WOLF-RAYET STAR WINDS
- Institute for Physics and Astronomy, University Potsdam, 14476 Potsdam (Germany)
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States)
- Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139 (United States)
- Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37663 (United States)
- European Space Agency XMM-Newton Science Operations Centre, European Space Astronomy Centre, Apartado 78, Villanueva de la Canada, 28691 Madrid (Spain)
We present the first high-resolution X-ray spectrum of a putatively single Wolf-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 Almost-Equal-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.
- OSTI ID:
- 22047732
- Journal Information:
- Astrophysical Journal Letters, Vol. 747, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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