  X-ray emission line profiles provide the most direct insight into the
dynamics and spatial distribution of the hot, X-ray-emitting plasma above the
surfaces of OB stars. The O supergiant zeta Puppis shows broad, blueshifted,
and asymmetric line profiles, generally consistent with the wind-shock picture.
We model the profiles of eight lines in the Chandra HETGS spectrum of this
prototypical hot star. The fitted lines indicate that the plasma is distributed
throughout the wind starting close to the photosphere, that there is
significantly less attenuation of the X-rays by the overlying wind than is
generally supposed, and that there is not a strong trend in wind absorption
with wavelength.
