2012ApJ...747L..25O -
Astrophys. J., 747, L25 (2012/March-2)
High-resolution X-ray spectroscopy reveals the special nature of Wolf-Rayet star winds.
OSKINOVA L.M., GAYLEY K.G., HAMANN W.-R., HUENEMOERDER D.P., IGNACE R. and POLLOCK A.M.T.
Abstract (from CDS):
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 ~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.
Abstract Copyright:
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Journal keyword(s):
stars: individual: WR 6 - stars: winds, outflows - stars: Wolf-Rayet - X-rays: stars
Errata:
erratum vol. 752, art. L35 (2012)
Simbad objects:
3
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