The first complete orbital solution for the double-lined spectroscopic binary system \gamma ^ { 2 } Velorum , obtained from measurements with the Sydney University Stellar Interferometer ( SUSI ) , is presented .
This system contains the closest example of a Wolf-Rayet star and the promise of full characterisation of the basic properties of this exotic high-mass system has subjected it to intense study as an archetype for its class .
In combination with the latest radial-velocity results , our orbital solution produces a distance of 336 ^ { +8 } _ { -7 } pc , significantly more distant than the Hipparcos estimation ( Schaerer et al . 55 ; van der Hucht et al . 77 ) .
The ability to fully specify the orbital parameters has enabled us to significantly reduce uncertainties and our result is consistent with the VLTI observational point ( 40 ) , but not with their derived distance .
Our new distance , which is an order of magnitude more precise than prior work , demands critical reassessment of all distance-dependent fundamental parameters of this important system .
In particular , membership of the Vela OB2 association has been reestablished , and the age and distance are also in good accord with the population of young stars reported by Pozzo et al .
( 51 ) .
We determine the O-star primary component parameters to be M _ { V } ( O ) = -5.63 \pm 0.10 mag , R ( O ) = 17 \pm 2 R _ { \sun } and { \cal M } ( O ) = 28.5 \pm 1.1 M _ { \sun } .
These values are consistent with calibrations found in the literature if a luminosity class of II–III is adopted .
The parameters of the Wolf-Rayet component are M _ { v } ( WR ) = -4.33 \pm 0.17 mag and { \cal M } ( WR ) = 9.0 \pm 0.6 M _ { \sun } .