Orbital-phased-resolved infrared spectra of Cygnus X-3 in outburst and quiescence , including tomographic analysis , are presented .
We confirm the phasing of broad He ii and N v lines in quiescence , such that maximum blue shift corresponds to the X-ray minimum at \Phi = 0.00 \pm 0.04 .
In outburst , double-peaked He i structures show a similar phasing with two significant differences : ( a ) although varying in relative strength , there is continuous line emission in blue and red peaks around the orbit , and ( b ) an absorption component , \sim 1 / 4 of an orbit out of phase with the emission features , is discerned .
Doppler tomograms of the double-peaked profiles are consistent with a disk-wind geometry , rotating at velocities of 1000 km s ^ { -1 } .
Regrettably , the tomography algorithm will produce a similar ring structure from alternative line sources if contaminated by overlying P Cygni profiles .
This is certainly the case in the strong 2.0587 \mu m He i line , leading to an ambiguous solution for the nature of double-peaked emission .
The absorption feature , detected 1/4 of an orbit out of phase with the emission features , is consistent with an origin in the He star wind and yields for the first time a plausible radial velocity curve for the system .
We directly derive the mass function of the system , 0.027 M _ { \odot } .
If we assume a neutron star accretor and adopt a high orbital inclination , i > 60 ^ { \circ } , we obtain a mass range for the He star of 5 M _ { \odot } \lesssim M _ { \mbox { \tiny WR } } \lesssim 11 M _ { \odot } .
Alternatively if the compact object is a black hole , we estimate M _ { \mbox { \tiny BH } } \lesssim 10 M _ { \odot } .
We discuss the implications of these masses for the nature and size of the binary system .