  Binary black holes as the recently detected sources of gravitational waves
can be formed from massive stellar binaries in the field or by dynamical
interactions in clusters of high stellar density, if the black holes are the
remnants of massive stars that collapsed without natal kicks that would disrupt
the binary system or eject the black holes from the cluster before binary black
hole formation. Here are summarized and discussed the kinematics in three
dimensions of space of five Galactic black hole X-ray binaries. For Cygnus X-1
and GRS 1915+105 it is found that the black holes of ~15 and ~10 solar masses
in these sources were formed in situ, without energetic kicks. These
observations suggest that binary black holes with components of ~10 solar
masses may have been prolifically produced in the universe.
