The Laser Interferometer Gravitational-Wave Observatory , LIGO , found direct evidence for double black hole binaries emitting gravitational waves .
Galactic nuclei are expected to harbor the densest population of stellar-mass black holes .
A significant fraction ( \sim 30 \% ) of these black holes can reside in binaries .
We examine the fate of the black hole binaries in active galactic nuclei , which get trapped in the inner region of the accretion disk around the central supermassive black hole .
We show that binary black holes can migrate into and then rapidly merge within the disk well within a Salpeter time .
The binaries may also accrete a significant amount of gas from the disk , well above the Eddington rate .
This could lead to detectable X-ray or gamma-ray emission , but would require hyper-Eddington accretion with a few percent radiative efficiency , comparable to thin disks .
We discuss implications for gravitational wave observations and black hole population studies .
We estimate that Advanced LIGO may detect \sim 20 such , gas-induced binary mergers per year .