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Radio emission from WR140

S. M. Dougherty·A. J. Beasley·M. J. Claussen·B. A. Zauderer·N. J. Bolingbroke
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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 to 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 degrees), the longitude of the ascending node (353+/-3 degrees), 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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S. M. Dougherty, A. J. Beasley, M. J. Claussen, B. A. Zauderer, N. J. Bolingbroke. 2004-10-07. Radio emission from WR140. https://arxiv.org/abs/astro-ph/0410211

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