Published online by Cambridge University Press: 14 August 2015
We have analysed new spectroscopic observations of 22 population I WR stars in a sample defined by b<12.5 mag, 18h<α<6h, δ > −30°. This completes the search for orbital duplicity among all of the 30 pop I WR stars contained within these limits. We thus have an unbiased data base in a volume segment bounded by a distance of 3–4 kpc for WNE and WC stars , and 4–5 kpc for WNL stars Although more observations are still needed in some cases, we have found several new binary systems. Some of these are low-amplitude, single-line binaries, often with runaway velocities and/or large separations from the galactic plane. We consider them to be candidates for a WR + collapsar stage, as originally predicted by Tutukov and Yungelson (1973) and de Loore and De Grève (1975).