It comes from a paper by Arizona State University physics professor Peter Rez that is scheduled to appear in a journal called Radiation Protection and Dosimetry.
Cherenkov radiation is predicted by the "standard model" of particle physics and is also observed in the real world, most often as a faint blue glow emanating from the cores of nuclear reactors.
We'd be able to connect a lot of the physics happening within the gaseous environment and accretion disk to the binary black hole merger to the gravitational radiation.