  We address the problem where the X-ray emission lines are formed and
investigate orbital dynamics using Chandra HETG observations, photoionizing
calculations and numerical wind-particle simulations.The observed Si XIV (6.185
A) and S XVI (4.733 A) line profiles at four orbital phases were fitted with P
Cygni-type profiles consisting of an emission and a blue-shifted absorption
component. In the models, the emission originates in the photoionized wind of
the WR companion illuminated by a hybrid source: the X-ray radiation of the
compact star and the photospheric EUV-radiation from the WR star. The emission
component exhibits maximum blue-shift at phase 0.5 (when the compact star is in
front), while the velocity of the absorption component is constant (around -900
km/s). The simulated FeXXVI Ly alpha line (1.78 A) from the wind is weak
compared to the observed one. We suggest that it originates in the vicinity of
the compact star, with a maximum blue shift at phase 0.25 (compact star
approaching). By combining the mass function derived with that from the
infrared HeI absorption (arising from the WR companion), we constrain the
masses and inclination of the system. Both a neutron star at large inclination
(over 60 degrees) and a black hole at small inclination are possible solutions.
