Atomic physics of shocked plasma in winds of massive stars

High resolution diffraction grating spectra of X-ray emission from massive stars obtained with Chandra and XMM-Newton have revolutionized our understanding of their powerful, radiation-driven winds. Emission line shapes and line ratios provide diagnostics on a number of key wind parameters. Modeling...

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Bibliographic Details
Main Authors: Leutenegger, Maurice A., Cohen, David H., Owocki, Stanley P., CRESST/UMBC, Swarthmore College, Swarthmore, PA 19081, Bartol Research Institute, University of Delaware, Newark, DE 19716
Format: Conference Proceeding
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COSMIC PHOTONS
COSMIC X-RAY SOURCES
DIFFRACTION GRATINGS
EMISSION SPECTRA
PLASMA DENSITY
PLASMA DIAGNOSTICS
PLASMA SIMULATION
RADIANT HEAT TRANSFER
RESCATTERING
RESONANCE SCATTERING
SPATIAL DISTRIBUTION
STARS
STELLAR RADIATION
STELLAR WINDS
X-RAY SPECTRA
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Summary:High resolution diffraction grating spectra of X-ray emission from massive stars obtained with Chandra and XMM-Newton have revolutionized our understanding of their powerful, radiation-driven winds. Emission line shapes and line ratios provide diagnostics on a number of key wind parameters. Modeling of resolved emission line velocity profiles allows us to derive independent constraints on stellar mass-loss rates, leading to downward revisions of a factor of a few from previous measurements. Line ratios in He-like ions strongly constrain the spatial distribution of Xray emitting plasma, confirming the expectations of radiation hydrodynamic simulations that X-ray emission begins moderately close to the stellar surface and extends throughout the wind. Some outstanding questions remain, including the possibility of large optical depths in resonance lines, which is hinted at by differences in line shapes of resonance and intercombination lines from the same ion. Resonance scattering leads to nontrivial radiative transfer effects, and modeling it allows us to place constraints on shock size, density, and velocity structure.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.4707864