Spectroscopic study of the short-period WN5o+O8.5V binary system WR127 (HD 186943)

Combined with previous information (orbital period P = 9.5550 d and inclination i = 55 degrees.5), new optical spectroscopic data lead to improved circular orbits for this WR + O system, with mass 13.4M(circle dot) of the WN5o star and 23.9M(circle dot) of its O8.5V companion. These are normal for their spectral types. The WR/O mass ratio, q similar or equal to 0.56, is reasonable for such a binary. The relatively large orbital separation between the two components (similar to 63 R(circle dot)) implies that there is currently no interaction between the two stars beyond their colliding winds. Analysis of the excess line emission and absorption arising in the wind-wind collision zone yields the following parameters: streaming velocity v(strm) = 1104 km s(-1), cone opening half-angle 0 similar or equal to 59 degrees and Coriolis angle shift delta phi = 8 degrees.1. Using probable values of mass-loss rate and terminal wind velocity for each star, a value of 0 similar or equal to 37 degrees is obtained. The difference in. is likely due to a combination of uncertainty in these parameters and radiative braking. Altogether, WR127 is a normal, detached and non-photospherically eclipsing binary system, although it does show atmospheric 'eclipses'.Peer reviewed: YesNRC publication: Ye