The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

  title={The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions},
  author={Gregor Rauw and Paul A. Crowther and Micha{\"e}l De Becker and Eric Gosset and Ya{\"e}l Naz{\'e} and Hugues Sana and Karel A. Hucht and J. M. Vreux and Peredur M. Williams},
  journal={Astronomy and Astrophysics},
We analyse the optical spectrum of the very massive binary system WR 20a (WN6ha + WN6ha). The most prominent emission lines, Hα and He  λ 4686, display strong phase-locked profile variability. From the variations of their equivalent widths and from a tomographic analysis, we find that part of the line emission probably arises in a wind interaction region between the stars. Our analysis of the optical spectrum of WR 20a indicates a reddening of AV � 6.0 mag and a distance of ∼7.9 kpc… 

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