When black holes collide, they produce a gravitational wave, as has been recently established by LIGO. When a charge is accelerated, it creates an electromagnetic wave.
Does an accelerated massive charge, such as a Reissner-Nordstrom black hole, or, more generally, a Kerr-Newman black hole, produce electromagnetic radiation? If so, how will the radiation behave in the highly curved space-time surrounding such objects?
(EDIT: The answer to this question, as given by Lawrence B. Crowell, is yes- at $r>>r_s$ the spacetime is flat and must behave classically, so massive compact charges will still produce radiation when accelerated, and the radiation as perceived by an observer at infinity must match the classical predictions.)
Will two colliding Kerr-Newman black holes create an electromagnetic wave as well as a gravitational wave? If so, will the two waves be somehow correlated or modulated by each other? Will they even coexist on the same plane? Will the spin of the black hole affect the produced radiation?
Is there a transfer of energy between the two waves, by means of some resonance with some coupling? If so, what will an observer at infinity accept to see, and how could he infer the parameters of the black hole from these observations?
In short: how will the gravitational and electromagnetic radiation produced in a collision of two Kerr-Newman black holes behave, both independently and with respect to one another?