  Progenitor models for the "luminous" subclass of Fast Blue Optical Transients
(LFBOTs; prototype: AT2018cow) are challenged to simultaneously explain all of
their observed properties: fast optical rise times < days; peak luminosities
>1e44 erg/s; low yields <0.1 Msun of 56Ni; aspherical ejecta with a wide
velocity range (<3000 km/s to > 0.1-0.5 c with increasing polar latitude);
presence of hydrogen-depleted-but-not-free dense circumstellar material (CSM)
on radial scales from ~1e14 cm to ~3e16 cm; embedded variable source of
non-thermal X-ray/gamma-rays, suggestive of a compact object. We show that all
of these properties are consistent with the tidal disruption and
hyper-accretion of a Wolf-Rayet (WR) star by a black hole (BH) or neutron star
(NS) binary companion. In contrast with related previous models, the merger
occurs with a long delay (>~ 100 years) following the common envelope (CE)
event responsible for birthing the binary, as a result of gradual angular
momentum loss to a relic circumbinary disk. Disk-wind outflows from the
merger-generated accretion flow generate the 56Ni-poor aspherical ejecta with
the requisite velocity range. The optical light curve is powered primarily by
reprocessing X-rays from the inner accretion flow/jet, though CSM shock
interaction also contributes. Primary CSM sources include mass-loss from WR
star (e.g., from the L2 point) during the earliest stages of the merger (~<1e14
cm) and the relic CE disk and its photoevaporation-driven wind (>~ 1e16 cm).
Longer delayed mergers may instead give rise to supernovae Type Ibn/Icn
(depending on the WR evolutionary state), potentially connecting these
transient classes with LFBOTs.
