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

• Published in: Monthly notices of the Royal Astronomical Society 2011-02, Vol.411 (1), p.635-643
• Main Authors: de la Chevrotière, A., Moffat, A. F. J., Chené, A.-N.
• Format: Article
• Language: English
• Subjects: Astronomy; binaries: spectroscopic; Double stars; Orbits; outflows; Spectrum analysis; stars: individual: WR127; stars: mass-loss; stars: winds; stars: winds, outflows; stars: Wolf-Rayet; techniques: spectroscopic
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2010.17710.x

Combined with previous information (orbital period P= 9.5550 d and inclination ), new optical spectroscopic data lead to improved circular orbits for this WR + O system, with mass 13.4 M⊙ of the WN5o star and 23.9 M⊙ of its O8.5V companion. These are normal for their spectral types. The WR/O mass ratio, q≃ 0.56, is reasonable for such a binary. The relatively large orbital separation between the two components (∼63 R⊙) 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 θ≃ 59° and Coriolis angle shift . Using probable values of mass-loss rate and terminal wind velocity for each star, a value of θ≃ 37° is obtained. The difference in θ 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'.