  We explore the ability of high energy observations to constrain orbital
parameters of long period massive binary systems by means of an inverse Compton
model acting in colliding wind environments. This is particular relevant for
(very) long period binaries where orbital parameters are often poorly known
from conventional methods, as is the case e.g. for the Wolf-Rayet (WR) star
binary system WR 147 where INTEGRAL and MAGIC upper limits on the high-energy
emission have recently been presented. We conduct a parameter study of the set
of free quantities describing the yet vaguely constrained geometry and
respective effects on the non-thermal high-energy radiation from WR 147. The
results are confronted with the recently obtained high-energy observations and
with sensitivities of contemporaneous high-energy instruments like Fermi-LAT.
For binaries with sufficient long periods, like WR 147, gamma-ray attenuation
is unlikely to cause any distinctive features in the high-energy spectrum. This
leaves the anisotropic inverse Compton scattering as the only process that
reacts sensitively on the line-of-sight angle with respect to the orbital
plane, and therefore allows the deduction of system parameters even from
observations not covering a substantial part of the orbit.
  Provided that particle acceleration acts sufficiently effectively to allow
the production of GeV photons through inverse Compton scattering, our analysis
indicates a preference for WR 147 to possess a large inclination angle.
Otherwise, for low inclination angles, electron acceleration is constrained to
be less efficient as anticipated here.
