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X-ray spectral diagnostics of activity in massive stars

Published online by Cambridge University Press:  12 July 2011

David H. Cohen ,
Emma E. Wollman  and
Maurice A. Leutenegger
David H. Cohen
Affiliation:
Department of Physics and Astronomy, Swarthmore College, 500 College Ave., Swarthmore, Pennsylvania, 19081, USA email: cohen@astro.swarthmore.edu
Emma E. Wollman
Affiliation:
Department of Physics, California Institute of Technology, Pasadena, California, 91125, USA email: ewollman@caltech.edu
Maurice A. Leutenegger
Affiliation:
NASA/Goddard Spaceflight Center, Code 662, Greenbelt, Maryland, 20771, USA email: maurice.a.leutenegger@nasa.gov
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Abstract

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X-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption signatures. In some cases, the degree of wind absorption is so high, that the hardening of the X-ray SED can be quite significant. We discuss these results as applied to the early O stars ζ Pup (O4 If), 9 Sgr (O4 V((f))), and HD 93129A (O2 If*).

Keywords

line: formationshock wavesstars: windsoutflowsX-rays: stars
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S272: Active OB stars: structure, evolution, mass loss, and critical limits , July 2010 , pp. 348 - 353
Copyright
Copyright © International Astronomical Union 2011

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