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Paper: Radio Emission from WR140
Volume: 367, Massive Stars in Interactive Binaries
Page: 271
Authors: Dougherty, S.M.; Beasley, A.J.; Claussen, M.J.; Zauderer, B.A.; Bolingbroke, N.J.
Abstract: Milliarcsecond resolution Very Long Baseline Array (VLBA) observations of the archetype WR+O star colliding-wind binary (CWB) system WR140 have been obtained at 23 epochs between orbital phases 0.74 and 0.97. The emission in the wind-collision region (WCR) is resolved as a bow-shaped arc which rotates as the orbital phase progresses. This rotation provides for the first time the inclination of the orbit (122° 5°), the longitude of the ascending node (353° 3°), and the orbit semi-major axis (9.0 0.5 mas). The implied distance is 1.85 0.16 kpc, which requires the O star to be a supergiant, and leads to a wind-momentum ratio of 0.22. Quasi-simultaneous Very Large Array (VLA) observations show the synchrotron spectra evolve dramatically through the orbital phases observed, exhibiting both optically thin and optically thick emission. The optically thin emission maintains a spectral index of −0.5, as expected from diffusive-shock acceleration.
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