  We present 18 years of OGLE photometry together with spectra obtained over 12
years, revealing that the early Oe star AzV 493 shows strong photometric (Delta
I < 1.2 mag) and spectroscopic variability with a dominant, 14.6-year pattern
and ~40-day oscillations. We estimate stellar parameters T_eff = 42000 K, log
L/L_sun = 5.83 +/- 0.15, M/M_sun = 50 +/- 9, and vsini = 370 +/- 40 km/s.
Direct spectroscopic evidence shows episodes of both gas ejection and infall.
There is no X-ray detection, and it is likely a runaway star. AzV 493 may have
an unseen companion on a highly eccentric (e > 0.93) orbit. We propose that
close interaction at periastron excites ejection of the decretion disk, whose
variable emission-line spectrum suggests separate inner and outer components,
with an optically thick outer component obscuring both the stellar photosphere
and the emission-line spectrum of the inner disk at early phases in the
photometric cycle. It is plausible that AzV 493's mass and rotation have been
enhanced by binary interaction followed by the core-collapse supernova
explosion of the companion, which now could be either a black hole or neutron
star. This system in the Small Magellanic Cloud can potentially shed light on
OBe decretion disk formation and evolution, massive binary evolution, and
compact binary progenitors.
