An Extensive Collection of Stellar Wind X-ray Source Region Emission Line Parameters,
Temperatures, Velocities, and Their Radial Distributions as Obtained from Chandra Observations of 17 OB Stars
Wayne L. Waldron (1), Joseph P. Cassinelli (2)
(1) Eureka Scientific, Inc., (2) University of Wisconsin-Madison
Chandra high energy resolution observations have now been obtained from numerous non-peculiar O and early B stars. We present a straightforward analysis of a broad collection of OB stellar line profile data to search for morphological trends. The line emission parameters and the spatial distributions of derived quantities are examined with respect to luminosity class. The X-ray spatial distributions are derived from the He-like ion f/i line ratios and X-ray temperatures are derived from the H-like to He-like line ratios. Our luminosity class study reveals line widths increasing with luminosity, and a small, but finite, blue-ward line-shift asymmetry which also increases with luminosity. However, the majority of emission lines are found to be symmetric with little central line displacement. Our spatial distribution study finds that the highest X-ray temperatures occur near the star and steadily decrease towards lower values in the outer wind regions. We find no evidence of any high temperature X-ray emission in the outer wind regions for any OB star. Since this is counter to basic shock model calculations, we call this the "near-star high-ion problem"
for OB stars. When using the traditional mass loss rates, we find a good correlation between the fir-inferred radii and their associated X-ray continuum optical depth unity radii. We discuss the significance of these anomalous X-ray results with regards to our current understanding of X-ray production in OB stellar winds.
Reference: ApJ, 668, in press
Status: Manuscript has been accepted