X-ray Spectroscopy of the Radiation-Driven Winds of Massive Stars: Line Profile and Line Ratio Diagnostics
David H. Cohen
备注：
Invited talk presented at the 16th International Conference on Atomic Processes in Plasmas, Monterey, CA, March 2009; will appear in an AIP-published conference proceedings. 10 pages, 4 figures (2 color, but color not crucial)
Massive stars drive powerful, supersonic winds via the radiative momentum associated with the thermal UV emission from their photospheres. Shock phenomena are ubiquitous in these winds, heating them to millions, and sometimes tens of millions, of degrees. The emission line spectra from the shock-heated plasma provide powerful diagnostics of the winds' physical conditions, which in turn provide constraints on models of wind shock heating. Here I show how x-ray line transfer is affected by photoelectric absorption in the partially ionized component of the wind and how it can be modeled to determine the astrophysically important mass-loss rates of these stellar winds. I also discuss how photoexcitation out of metastable excited levels of helium-like ions can provide critical information about the location of the hot plasma in magnetically channeled massive star winds.
Polarization Diagnostics Applied to Coronal Mass Ejections and the Background Solar Wind
National Center for Atmospheric Research（国家大气研究中心）；Southwest Research Institute（西南研究所）；CIRES, University of Colorado（科罗拉多大学联合空间环境研究中心）；University of Colorado（科罗拉多大学）；Aberystwyth University（阿伯里斯特威斯大学）；Johns Hopkins University（约翰斯·霍普金斯大学）；Boston College（波士顿学院）
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Observations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resoluti…
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