  Recent work on Cygnus X-2 suggests that neutron-star or black-hole binaries
survive highly super-Eddington mass transfer rates without undergoing
common-envelope evolution. We suggest here that the accretion flows in such
cases are radiation pressure-dominated versions of the "ADIOS" picture proposed
by Blandford and Begelman (1999), in which almost all the mass is expelled from
large radii in the accretion disk. We estimate the maximum radius from which
mass loss is likely to occur, and show that common-envelope evolution is
probably avoided in any binary in which a main-sequence donor transfers mass on
a thermal timescale to a neutron star or black hole, even though the mass
transfer rate may reach values of 0.001 solar masses per year. This conclusion
probably applies also to donors expanding across the Hertzsprung gap, provided
that their envelopes are radiative. SS433 may be an example of a system in this
state.
