Hubble Space Telescope detection of optical companions of WR 86, WR 146, and WR 147: Wind collision model confirmed

Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of the rado-binary Wolf-Rayet stars WR 146 and WR 147, as well as the 0.2 " visual binary WR 86, resolve each of them into two very close optical components. The colors of these optical pairs are similar, indicating that they are likely to be physically bound WR + OB systems at the same distance. Comparison of the locations of the optical components of WR 146 and WR 147 with high-resolution radio maps strikingly demonstrates that the nonthermal radio components arise between the optical binary components, closer to the OB component than the WR. This is as expected if the nonthermal radio emission results from the collision of the stellar winds of the binary components seen in the HST images. The similar magnitudes and colors determined for the components of WR 86 from our HST images, combined with an analysis of the unresolved, combined WC7 + OB optical spectrum, indicates an absolute magnitude for the WC7 component of about M-V similar to -5.