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- The Orbit and Distance of WR140
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The Orbit and Distance of WR140
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Annexes
Abstract
A campaign of 35 epochs of milli-arcsecond resolution VLBA observations of the archetype colliding-wind WR+O star binary system WR140 show the wind-collision region (WCR) as a bow-shaped arc of emission that rotates as the highly eccentric orbit progresses. The observations comprise 21 epochs from the 1993-2001 orbit, discussed by Dougherty et al. (2005), and 14 epochs from the 2001-2009 orbit, and span orbital phase 0.43 to 0.95. Assuming the WCR is symmetric about the line-of-centres of the two stars and “points” at the WR star, this rotation shows the O star moving from SE to E of the WR star between these orbital phases. Using IR interferometry observations from IOTA that resolve both stellar components at phase 0.297 in conjunction with orbital parameters derived from radial velocity variations, the VLBA observations constrain the inclination of the orbit plane as 120°±4°, the longitude of the ascending node as 352°±2°, and the orbit semimajor axis as 9.0±0.1 mas. This leads to a distance estimate to WR140 of 1.81±0.08 kpc. Further refinements of the orbit and distance await more IR interferometric observations of the stellar components directly.
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A propos de : S.M. Dougherty
NRC-HIA DRAO, Penticton, BC, Canada, and Institute for Space Imaging Science, University of Calgary, AB, Canada
A propos de : V. Trenton
NRC-HIA DRAO, Penticton, BC, Canada, and University of Prince Edward Island, Charlottetown, PEI, Canada
A propos de : A.J. Beasley
National Ecological Observatory Network, Boulder, Colorado, USA