Circumstellar Dynamics At High Resolution: Proceedings Of A Joint ESO/Brazilian Workshop
ASP Conference Series
High-resolution X-ray grating spectroscopy enables us to measure the kinematics and spatial distribution of the shock-heated wind plasma in O and early B stars, testing the predictions of the embedded wind shock scenario of massive star X-ray production. By fitting models to the resolved, Doppler broadened X-ray emission line profiles measured by the Chandra X-ray Observatory's grating spectrometer, we find an onset radius of X-ray production of roughly Ro = 1.5 R★ for the O supergiants, ζ Pup and HD 93129A. From the profile fitting we also find that the terminal velocity of the X-ray emitting plasma is consistent with that of the bulk, UV absorbing wind. We also use the X-ray emission line profiles to measure the wind mass-loss rates and break the degeneracy between mass-loss rate and clumping factor that affects traditional Hα and radio free-free diagnostics. We find clumping factors of order fcl = 10, which also agrees with the simulations of the wind instability. And we find that clumping begins very close to the photosphere, significantly lower in the wind than the onset of X-ray production. For lower density B star winds, the X-ray emission lines are much narrower than in the O supergiants, and are inconsistent with the hot plasma sharing the kinematics of the bulk wind.
Astronomical Society of the Pacific
A. C. Carciofi, and T. Rivinius, eds.
Joint ESO/Brazilian Workshop on Circumstellar Dynamics at High Resolution
February 27 - March 2, 2012
Foz do Iguaçu, Brazil
David H. Cohen.
"The X-Ray View Of OB Star Wind Structure And Dynamics".
Circumstellar Dynamics At High Resolution: Proceedings Of A Joint ESO/Brazilian Workshop.
This work is freely available courtesy of the Astronomical Society of the Pacific Conference Series.