Title

The X-Ray View Of OB Star Wind Structure And Dynamics

Document Type

Conference Proceeding

Publication Date

12-1-2012

Published In

Circumstellar Dynamics At High Resolution: Proceedings Of A Joint ESO/Brazilian Workshop

Abstract

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.

Published By

Astronomical Society of the Pacific

Editor(s)

A. C. Carciofi, and T. Rivinius, eds.

Conference

Joint ESO/Brazilian Workshop on Circumstellar Dynamics at High Resolution

Conference Dates

February 27 - March 2, 2012

Conference Location

Foz do Iguaçu, Brazil