We present a new analysis of an archived Chandra HETGS X-ray spectrum of the WR+O colliding wind binary \gamma ^ { 2 } Velorum .
The spectrum is dominated by emission lines from astrophysically abundant elements : Ne , Mg , Si , S and Fe .
From a combination of broad-band spectral analysis and an analysis of line flux ratios we infer a wide range of temperatures in the X-ray emitting plasma ( \sim 4–40 MK ) .
As in the previously published analysis , we find the X-ray emission lines are essentially unshifted , with a mean FWHM of 1240 \pm 30 \mbox { ~ { } km } \mbox { ~ { } s } ^ { -1 } .
Calculations of line profiles based on hydrodynamical simulations of the wind-wind collision predict lines that are blueshifted by a few hundred \mbox { ~ { } km } \mbox { ~ { } s } ^ { -1 } .
The lack of any observed shift in the lines may be evidence of a large shock-cone opening half-angle ( > 85 \degr ) , and we suggest this may be evidence of sudden radiative braking .
From the R and G ratios measured from He-like forbidden-intercombination-resonance triplets we find evidence that the Mg xi emission originates from hotter gas closer to the O star than the Si xiii emission , which suggests that non-equilibrium ionization may be present .