  We analyze multicolor light curves and high resolution optical spectroscopy
of the eclipsing binary and Double Periodic Variable OGLE 05155332-6925581.
According to Mennickent et al., this system shows a significant change in the
long non-orbital photometric cycle, a loop in the color-magnitude diagram
during this cycle and discrete spectral absorption components that were
interpreted as evidence of systemic mass loss. We find that the best fit to the
multi-band light curves requires a circumprimary optically thick disc with a
radius about twice the radius of the more massive star. The spectroscopy
indicates a mass ratio of 0.21+-0.02 and masses for the hot and cool stars of
9.1+-0.5 and 1.9+-0.2 M_sun, respectively. A comparison with synthetic
binary-star evolutionary models indicates that the system has an age of 4.76E7
years, is in the phase of rapid mass transfer, the second one in the life of
this binary, in a Case-B mass-exchange stage. Donor-subtracted H_alpha profiles
show the presence of double emission formed probably in an optically thin
circumstellar medium, while the variable HeI profile and the H_beta absorption
wings are probably formed in the optically thick circumprimary disc. The model
that best fit the observations shows the system with a relatively large mass
transfer rate of dM/dt = 3.1E-6 M_sun/yr. However, the orbital period remains
relatively stable during almost 15 years. This observation suggests that the
hot-spot mass-loss model proposed by other authors is not adequate in this
case, and that some other mechanism is efficiently removing angular momentum
from the binary. Furthermore, our observations suggest that the DPV phenomenon
could have an important effect in the balance of mass and angular momentum in
the system.
