X-raying clumped stellar winds

  • X-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location of the hottest X-ray emitting plasma very close to the base of the wind, perhaps indicating the presence of a corona, while measurements from lower ions conform with the wind-embedded shock model. Generally, to correctly model the emerging Xray spectra, a detailed knowledge of the cool wind opacities based on stellar atmosphere models is prerequisite. A nearly grey stellar wind opacity for the X-rays is deduced from the analyses of high-resolution X-ray spectra. This indicates that the stellar winds are strongly clumped. Furthermore, the nearly symmetric shape of X-ray emission line profiles can be explained if the wind clumps are radiallyX-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location of the hottest X-ray emitting plasma very close to the base of the wind, perhaps indicating the presence of a corona, while measurements from lower ions conform with the wind-embedded shock model. Generally, to correctly model the emerging Xray spectra, a detailed knowledge of the cool wind opacities based on stellar atmosphere models is prerequisite. A nearly grey stellar wind opacity for the X-rays is deduced from the analyses of high-resolution X-ray spectra. This indicates that the stellar winds are strongly clumped. Furthermore, the nearly symmetric shape of X-ray emission line profiles can be explained if the wind clumps are radially compressed. In massive binaries the orbital variations of X-ray emission allow to probe the opacity of the stellar wind; results support the picture of strong wind clumping. In high-mass X-ray binaries, the stochastic X-ray variability and the extend of the stellar-wind part photoionized by X-rays provide further strong evidence that stellar winds consist of dense clumps.show moreshow less

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Metadaten
Author:Lidia M. Oskinova, Wolf-Rainer Hamann, Achim Feldmeier
URN:urn:nbn:de:kobv:517-opus-18133
Document Type:Conference Proceeding
Language:English
Date of Publication (online):2008/04/25
Year of Completion:2007
Publishing Institution:Universität Potsdam
Release Date:2008/04/25
RVK - Regensburg Classification:US 1999.07
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften
Collections:Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007
Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007 / Talks and Discussions (in alphabetical order)
Universität Potsdam / Tagungen / Clumping in hot-star winds: International Workshop, Potsdam, Germany, 18. - 22. June 2007 / Talks and Discussions (organized by sections) / X-rays
Licence (German):License LogoKeine Nutzungslizenz vergeben - es gilt das deutsche Urheberrecht
Notes extern:
The complete edition of the proceedings "Clumping in hot-star winds" is available:
urn:nbn:de:kobv:517-opus-13981