July 11-15, 2011
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The orbit & proper motion of WR140 from high-resolution radio imaging.

Sean Dougherty (NRC)

Ian A. Smith (UWaterloo)

Thirty-six high-resolution VLBA observations of the archetype wind-colliding binary system WR140 between 1999 and 2008 reveal the motion of the wind-collision region during two orbit cycles. This motion is a combination of the proper motion and the orbital motion of the binary system. Using the orbital parameters derived from optical spectroscopy (Fahed et al. 2011) to calculate the separation vector between the two stars as a function of orbital phase, the orbit can be fully defined, complete with a precise distance estimate independent of stellar parameters. The proper motion of the centre of mass and its distance from the wind-collision region (WCR) is determined through fitting the motion of the WCR across the sky. This constrains the relationship between mass-ratio and the wind-momentum ratio of the two stars, and the stellar masses in the system.
(to be confirmed by the SOC)