  A re-examination of high-resolution spectral monitoring of the W UMa-type
binaries AW UMa and Epsilon CrA casts doubt on the widely utilized Lucy (1968a,
1968b) model of contact binaries. The detection of the very faint profile of
the secondary component in AW UMa leads to a new spectroscopic determination of
the mass ratio, q(sp) = 0.092 +/- 0.007, which is close to the previous,
medium-resolution spectroscopic result of Pribulla & Rucinski (2008), q(sp) =
0.101 +/- 0.006, and remains substantially different from a cluster of
generally accepted photometric results by several authors, concentrated around
q(ph) = 0.080 +/- 0.005. The two approaches are independent, with the
spectroscopic technique being more direct yet more demanding on
telescope/spectrograph resources, while the photometric determinations are
accessible to smaller telescopes but entirely dependent on the Lucy model. A
survey of binaries with the best-determined values of the mass ratio shows a
common tendency for q(ph) < q(sp). The tendency for systematically smaller
values of q(ph) may result from the overfilling of the primary lobe and
underfilling of the secondary lobe relative to the Roche model geometry, as
predicted by the Stepien (2009) model; the tendency may be variable in time.
Despite the observed moderate inter-systemic velocities, the photometric Lucy
model may remain useful in providing approximate, though biased, results for
the mass ratio. A complicating factor in detailed spectral analysis may be the
occurrence of Enhanced Spectral-line Perturbations (ESP) projected over the
secondary profiles, appearing in different numbers in the two studied binaries.
The ESPs are tentatively identified within the Stepien model as collision
fronts or fountains of hot, primary-component gas from the circumbinary,
energy-carrying flow.
