  Accurate photometric CoRoT space observations of a secondary seismological
target, HD 174884, led to the discovery that this star is an astrophysically
important double-lined eclipsing spectroscopic binary in an eccentric orbit (e
of about 0.3), unusual for its short (3.65705d) orbital period. The high
eccentricity, coupled with the orientation of the binary orbit in space,
explains the very unusual observed light curve with strongly unequal primary
and secondary eclipses having the depth ratio of 1-to-100 in the CoRoT 'seismo'
passband. Without the high accuracy of the CoRoT photometry, the secondary
eclipse, 1.5 mmag deep, would have gone unnoticed. A spectroscopic follow-up
program provided 45 high dispersion spectra. The analysis of the CoRoT light
curve was performed with an adapted version of PHOEBE that supports CoRoT
passbands. The final solution was obtained by simultaneous fitting of the light
and the radial velocity curves. Individual star spectra were derived by
spectrum disentangling. The uncertainties of the fit were derived by bootstrap
resampling and the solution uniqueness was tested by heuristic scanning. The
results provide a consistent picture of the system composed of two late B
stars. The Fourier analysis of the light curve fit residuals yields two
components, with orbital frequency multiples and an amplitude of about 0.1
mmag, which are tentatively interpreted as tidally induced pulsations. An
extensive comparison with theoretical models is carried out by means of the
Levenberg-Marquardt minimization technique and the discrepancy between models
and the derived parameters is discussed. The best fitting models yield a young
system age of 125 million years which is consistent with the eccentric orbit
and synchronous component rotation at periastron.
