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X-ray Emission from O Stars

Published online by Cambridge University Press:  01 December 2007

David H. Cohen
David H. Cohen*
Affiliation:
Swarthmore College, Department of Physics and Astronomy, 500 College Ave., Swarthmore, Pennsylvania 19081, USA
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Abstract

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Young O stars are strong, hard, and variable X-ray sources; properties that strongly affect their circumstellar and galactic environments. After ≈ 1 Myr, these stars settle down to become steady sources of soft X-rays. I will use high-resolution X-ray spectroscopy and MHD modeling to show that young O stars like θ1 Ori C are well explained by the magnetically channeled wind shock scenario. After their magnetic fields dissipate, older O stars produce X-rays via shock heating in their unstable stellar winds. Here too I will use X-ray spectroscopy and numerical modeling to confirm this scenario. In addition to elucidating the nature and cause of the O star X-ray emission, modeling of the high-resolution X-ray spectra of O supergiants provides strong evidence that mass-loss rates of these O stars have been overestimated.

Keywords

hydrodynamics – instabilities – line: profiles – magnetic fields – MHD – shock waves – stars: early type – stars: mass loss – stars: windsoutflows – X-rays: stars
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S250: Massive Stars as Cosmic Engines , December 2007 , pp. 17 - 24
Copyright
Copyright © International Astronomical Union 2008

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