Accretion and outflow in the gamma ray bursts from black hole binary
  systems
  We consider a scenario for the longest duration gamma ray bursts, resulting
from the collapse of a massive star in a close binary system with a companion
black hole. The primary black hole born during the core collapse is spun up and
increases its mass during the fallback of the stellar envelope. The companion
black hole provides an additional angular momentum to the envelope, which
ultimately makes the core BH spinning with a high Kerr parameter. After the
infall and spiral-in, the two black holes merge inside the circumbinary disk.
The second episode of mass accretion and final, even larger spin of the
post-merger black hole prolongs the gamma ray burst central engine activity.
The observed events should have two distinct peaks in the electromagnetic
signal, separated by the gravitational wave emission. The gravitational recoil
of the burst engine is also possible.
