  The problem of explaining the X-ray emission properties of the massive, close
binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR
20a is composed of two nearly identical Wolf- Rayet stars of 82 and 83 solar
masses orbiting with a period of only 3.7 days. Although Chandra observations
were taken during the secondary optical eclipse, the X-ray light curve shows no
signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous
and softer during the optical eclipse, opposite to what has been observed in
other binary systems. To aid in our interpretation of the data, we compare with
the results of hydrodynamical simulations using the adaptive mesh refinement
code Mezcal that includes radiative cooling and a radiative acceleration force
term. It is shown that the X-ray emission can be successfully explained in
models where the wind-wind collision interface in this system occurs while the
outflowing material is still being accelerated. Consequently, WR 20a serves as
a critical test-case for how radiatively-driven stellar winds initiate and
interact. Our models not only procure a robust description of current Chandra
data, which cover the orbital phases between 0.3 to 0.6, but provide detailed
predictions over the entire orbit.
