Context : Aims : We address the problem where the X-ray emission lines are formed and investigate orbital dynamics using \it { Chandra } HETG observations , photoionizing calculations and numerical wind-particle simulations . The aims were to set constraints on the masses of the components of this close binary system consisting of a Wolf-Rayet ( WR ) star and a compact component and to investigate the nature of the latter ( neutron star or black hole ) . The goal was also to investigate P Cygni signatures in line profiles . Methods : The observed Si xiv ( 6.185 Ã ) and S xvi ( 4.733 Ã ) line profiles at four orbital phases were fitted with P Cygni-type profiles consisting of an emission and a blue-shifted absorption component . Numerical models were constructed using photoionizing calculations and particle simulations . 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 . Results : Spectral lines with moderate excitation ( such as Si xiv and S xvi ) arise in the photoionized wind . 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 ) . Both components , like the continuum flux , have intensity maxima around phase 0.5 . The simulated Fe xxvi Ly \alpha line ( 1.78 Ã , H-like ) 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 He i absorption ( arising from the WR companion ) , we constrain the masses and the inclination of the system . Conclusions : The Si xiv and S xvi lines and their radial velocity curves can be understood in the framework of a photoionized wind involving a hybrid ionizer . Constraints on the compact star mass and orbital inclination ( i ) are given using the mass functions derived from the Fe xxvi line and He i 2.06 \mu m absorption . Both a neutron star at large inclination ( i \geq { 60 } degrees ) and a black hole at small inclination are possible solutions . The radial velocity amplitude of the He ii 2.09 \mu m emission ( formed in the X-ray shadow behind the WR star ) suggests i = 30 degrees , implying a possible compact star mass between 2.8 – 8.0 M _ { \sun } . For i = 60 degrees the same range is 1.0 – 3.2 M _ { \sun } .