A press release on “Black Hole Spin Cranks-up Radio Volume” (NAOJ).

Are Spinning Black Holes Louder?” (AAS Nova).
For kids, “Black Hole Spin Turns-up the Radio” .

These results were published as “Evidence for Higher Black Hole Spin in Radio-loud Quasars” by Schulze, Inoue, et. al. in the Astrophysical Journal in November 2017.