  We discuss the electromagnetic radiation from newborn binary black holes
(BBHs). As a consequence of the evolution of massive stellar binaries, a binary
consisting of a primary black hole (BH) and a secondary Wolf-Rayet star is
expected as a BBH progenitor system. We investigate optical transients from the
birth of BBHs powered by the Bondi-Hoyle-Lyttleton accretion onto the primary
BH, which occur $\sim1-10$ Gyr earlier than gravitational wave signals at the
BH-BH merger. When the secondary massive star collapses into a BH, it may eject
a fraction of its outer material and may form a disk around the primary BH and
induces a powerful disk wind. These primary-induced winds can lead to optical
transients with a kinetic energy of $\sim10^{47}-3\times10^{48}$ erg, an ejecta
velocity of $10^8-10^9\rm~cm~s^{-1}$, a duration of a few days, and an absolute
magnitude ranging from about $-11$ to $-14$. The light curves and late-time
spectra of these transients are distinctive from those of ordinary supernovae,
and detection of this type of transient is possible by future optical transient
surveys if the event rate of this transient is comparable to the merger rate of
BBHs. This paper focuses on the emissions from disk-driven transients induced
by the primary BH, different from the first paper that focuses on wind-driven
transients from the tidally-locked secondary massive star.
