ICCD speckle observations of binary stars. XXII. A survey of Wolf-Rayet stars for close visual companions

We present the results of a speckle interferometric survey for close visual companions, mainly among 29 of the apparently brightest Wolf-Rayet (W-R) stars. Only one target, WR 48 = theta Mus, was resolved as a close astrometric binary (with a separation of 46 +/- 9 mas). This system is probably a triple comprising a short-period W-R binary plus a distant O supergiant companion. Although our binary detection fraction is low, it is not an unexpected result given the selection effects that militate against easy detection of binaries. New, higher resolution observations will almost certainly increase the fraction of binaries. There are four known binaries among the six W-R stars in our sample that have nonthermal radio emission, and this connection supports the idea that the nonthermal emission originates in the wind-wind collision between components.