  The parameter space favourable for the resonant excitation of free
oscillation modes by dynamic tides in close binary components is explored using
qualitative considerations to estimate the order of magnitude of the tidal
force and the frequency range covered by the tidally induced oscillations. The
investigation is valid for slowly rotating stars with masses in the interval
between 2 and 20 solar masses, and an evolutionary stage ranging from the
beginning to the end of the main sequence. Oscillation modes with
eigenfrequencies of the order of five times the inverse of the star's dynamical
time scale - i.e. the lowest-order p-modes, the f-mode, and the lowest-order
g-modes - are found to be outside the favourable parameter space since their
resonant excitation requires orbital eccentricities that are too high for the
binary to stay detached when the components pass through the periastron of
their relative orbit. Resonances between dynamic tides and g-modes with
frequencies of the order of half of the inverse of the star's dynamical time
scale on the other hand are found to be favourable for orbital periods up to
200 times the star's dynamical time scale, provided that the binary mass ratio
q is larger than 1/3 and the orbital eccentricity e is larger than
approximately 0.25. This favourable range comes down to orbital periods of up
to 5-12 days in the case of 2-20 solar mass zero-age main-sequence binary
components, and orbital periods of up to 21-70 days in the case of terminal
main-sequence binary components.
