X-ray emission from O stars

David H. Cohen

Swarthmore College, Department of Physics and Astronomy

Young O stars are strong, hard, and variable X-ray sources, properties which strongly affect their circumstellar and galactic environments. After ~1 Myr, these stars settle down to become steady sources of soft X-rays. I use high-resolution X-ray spectroscopy and MHD modeling to show that young O stars like theta-1 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 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.

Reference: To appear in IAU Symposium 250, "Massive Stars as Cosmic Engines," Kauai, HI, December 2007; eds. Bresolin, Crowther, & Puls, Cambridge University Press, 2008.
Status: Conference proceedings

Weblink: http://astro.swarthmore.edu/~cohen/papers/cohen_OstarXrays_color_kauai2007.pdf

Comments: This version of the paper includes the post-talk Q&A transcript as well as one extra figure. Many of the figures are in color. A b/w version without the extra figure is also available: http://astro.swarthmore.edu/~cohen/papers/cohen_OstarXrays_bw_kauai2007.pdf

Email: cohen@astro.swarthmore.edu