  Strong wind-wind collisions in massive binaries generate a very hot plasma
that frequently produces a moderately strong iron line. The morphology of this
line depends upon the properties of the wind interaction zone and its
orientation with respect to the line of sight. As the binary components revolve
around their common centre of mass, the line profiles are thus expected to
vary. With the advent of the next generation of X-ray observatories (Astro-H,
Athena) that will offer high-resolution spectroscopy above 6 keV, it will
become possible to exploit these changes as the most sensitive probe of the
inner parts of the colliding wind interaction. Using a simple prescription of
the wind-wind interaction in an early-type binary, we have generated synthetic
line profiles for a number of configurations and orbital phases. These profiles
can help constrain the properties of the stellar winds in such binary systems.
