Abstract
The detection of the gravitational wave (GW) source GW150914 by the
advanced Laser Interferometer Gravitational Wave Observatory (aLIGO)
was interpreted as the merger of a binary black hole (BBH). A conventional
model of a binary black holes is supposed to consist of two black holes
of different masses which were born long ago before merger. A merger of
two black holes in vacuum is expected to have no electromagnetic radiation
in general. At the same time the Gamma-ray Burst Monitor (GBM) on board
the Fermi satellite reported the detection of a transient electromagnetic
signal. Recently, A.Loeb considered new model in which binary black
hole was created few minutes before coalescence. I consider the rate of
such GW events.