AAS 207th Meeting Abstract Submission

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\datesubmitted{2005-10-19 12:10:31}
\authorphone{(610) 328-8587}
\correspondentaddress{St. John's College, 60 College Ave., Annapolis MD 21401}
\sponsor{David H. Cohen}

\title{Wind Signatures in the X-ray Emission Line Profiles of the O Supergiant zeta Orionis}
\authoraffil{St. John's College}
\authorgivenname{D. H.}
\authoraffil{Swarthmore College}
\authorgivenname{M. A.}
\authoraffil{Columbia University}
\authoraffil{Swarthmore College}
\authorgivenname{R. H.}
\authoraffil{Columbia University}
\authorgivenname{S. P.}
\authoraffil{University of Delaware}

The profiles of X-ray emission lines from several hot stars 
are resolved by the Chandra grating spectrometers. These 
profile shapes provide information about the kinematics of 
the hot plasma around these stars and, via signatures of 
continuum attenuation, also provide information about the 
overlying cold stellar wind. We present a quantitative 
analysis of roughly one dozen emission lines in the Chandra 
HETGS spectrum of zeta Ori (O 9.7 Ib), and analyze the 
results in the context of the line-force instability shock 
model. The distribution in velocity space of the emission, 
along with the separate helium-like line ratio results, are 
consistent with the wind-shock scenario. But, although there 
is statistically significant evidence for some wind 
attenuation, the degree of wind attenuation is a factor of 
five to ten less than what would be expected in the context 
of a smooth, spherically symmetric wind and the UV-derived 
wind mass-loss rate. These results are consistent with those 
derived from the X-ray emission line profiles of the hotter 
O star, zeta Pup, and also with recent, independent evidence 
from UV spectroscopy, that O star mass-loss rates have been 

We acknowledge support from NASA contract NAS8-03060 and 
from the National Science Foundation, through their REU 
program at the Keck Northeast Astronomy Consortium, via 
contract AST-0353997.

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