  We present spatially resolved spectra of the visual WR+OB massive binaries
WR86, WR146, and WR147, obtained with the Space Telescope Imaging Spectrograph
on board the Hubble Space Telescope. The systems are classified as follows:
WR86 = WC7 + B0 III, WR146 = WC6 + O8 I-IIf, WR147 = WN8 + O5-7 I-II(f). Both
WR146 and WR147 are known to have strong non-thermal radio emission arising in
a wind-wind collision shock zone between the WR and OB components. We find that
the spectra of their O companions show Halpha profiles in emission, indicative
of large mass-loss rates, and consistent with the colliding-wind model. Our
spectra indicate that the B component in WR86 has a low mass-loss rate, which
possibly explains the fact that WR86, despite being a long period WR+OB binary,
was not found to be a strong non-thermal radio emitter. Because of the small
mass-loss rate of the B star component in WR86, the wind collision region must
be closer to the B star and smaller in effective area, hence generating smaller
amounts of non-thermal radio emission. Absolute magnitudes for all the stars
are estimated based on the spectral types of the components (based on the
tables by Schmidt-Kaler for OB stars, and van der Hucht for WR stars), and
compared with actual, observed magnitude differences. While the derived
luminosities for the WC7 and B0 III stars in WR86 are consistent with the
observed magnitude difference, we find a discrepancy of at least 1.5 magnitudes
between the observed luminosities of the components in each of WR146 and WR147
and the absolute magnitudes expected from their spectral types. In both cases,
it looks as though either the WR components are about 2 magnitudes too bright
for their spectral types, or that the O components are about 2 magnitudes too
faint. We discuss possible explanations for this apparent discrepancy.
