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

Authors

  • A. de la Chevrotière,

    Corresponding author
    1. Département de Physique, Université de Montréal, and Centre de Recherche en Astrophysique du Québec, CP 6128, Succursale A, Montréal, QC H3C 3J7, Canada
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  • A. F. J. Moffat,

    Corresponding author
    1. Département de Physique, Université de Montréal, and Centre de Recherche en Astrophysique du Québec, CP 6128, Succursale A, Montréal, QC H3C 3J7, Canada
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  • A.-N. Chené

    Corresponding author
    1. Canadian Gemini Office, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
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E-mail: antoine@astro.umontreal.ca (AdlC); moffat@astro.umontreal.ca (AFJM); andre-nicolas.chene@nrc-cnrc.gc.ca (A-NC)

ABSTRACT

Combined with previous information (orbital period P= 9.5550 d and inclination inline image), 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 vstrm= 1104 km s−1, cone opening half-angle θ≃ 59° and Coriolis angle shift inline image. 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’.

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