The blue stars surrounding the black hole are no more than 200 million years old, and therefore must have
formed near the black hole in an abrupt burst of star formation.
Based on their observations, they have concluded that the rate of a TDE occurring increases «dramatically» when two galaxies are colliding, most likely due to the fact that such events cause a large number of stars to be
formed near the central supermassive
black holes of the merging systems.
This ultra-powerful field becomes better organized and
forms two outwardly directed funnels along the new
black hole's rotational axis, which then creates the two bi-polar jets of particles moving
near the speed of light that are detected as a short GRB (NASA news release; Seil Collins, New Scientist, April 13, 2011; and Rezzolla et al, 2011; and more discussion and images from Bruno Giacomazzo's presentation).