The mass of the very massive binary WR21a

  title={The mass of the very massive binary WR21a},
  author={Frank Tramper and Hugues Sana and N. E. Fitzsimons and Alex de Koter and Lex Kaper and Laurent Mahy and Anthony F. J. Moffat},
  journal={Monthly Notices of the Royal Astronomical Society},
We present multi-epoch spectroscopic observations of the massive binary system WR21a, which include the 2011 January periastron passage. Our spectra reveal multiple SB2 lines and facilitate an accurate determination of the orbit and the spectral types of the components. We obtain minimum masses of 64.4 ± 4.8 M⊙ and 36.3 ± 1.7 M⊙ for the two components of WR21a. Using disentangled spectra of the individual components, we derive spectral types of O3/WN5ha and O3Vz ((f*)) for the primary and… 

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