MERLIN observations of WR 147 (WN8(h)+B0.5V)

Abstract

WR147 was first discovered to be a strong radio, X-ray and infra-red emission source by Caillault et al. (1985). It was classified as a WN8 type star with a very large mass loss rate and unusual radio emission (α < 0) for a thermal source. This unusual behaviour was explained by MERLIN (Moran et al. 1989) and VLA (Churchwell et al. 1992) observations in which it was resolved into two components: a ‘thermal’ source associated with the Wolf-Rayet star and a non-thermal component ∼ 600 mas to the north. Churchwell et al. showed that the southern component had the expected spectral index of α ≃ 0.6 for free-free emission from a stellar wind. They also showed that the northern component had a spectral index of α ≃ −0.5 and was therefore a non-thermal source, now thought to be due to a colliding wind region.