  By means of population synthesis we find that the expected Galactic number of
black holes with massive helium star companions is \sim 100 and depends on an
assumed threshold for M_{pre-BH}. The overwhelming majority of these systems
has orbital periods in excess of 10 hr, with a maximum at \sim 100 hr, while
under the Illarionov & Sunyaev (1975) disk formation criteria for accretion
from the strong stellar wind of Wolf-Rayet star disk accretion is possible only
for orbital periods below \sim 10 hr. However, the number of such short-period
systems is vanishingly small. If the accretor in Cyg X-3 is a 10 M_sun black
hole, then the accretion rate will be super-Eddington. Super-Eddington
accretion may be responsible for the formation of jets in Cyg X-3 and may also
support an X-ray luminosity as high as \sim 10^{39} erg/s. From the orbital
period distribution for neutron stars with massive helium companions we find
that if during the common envelope phase a neutron star accretes at Eddington
rate and spins-up to the equilibrium period, then in most systems it acts as a
``propeller'' and accretion from the WR star wind is impossible. For the model
with two massive helium stars as an immediate progenitor of Cyg X-3,
requirement of accomodation of two WR stars in the post-common-envelope orbit
combined with severe mass loss by them prevents formation of BH+WR systems with
orbital periods less than several days.

Astrophysics