Blandford-Znajek mechanism in black holes in alternative theories of   gravity
  According to the Blandford-Znajek mechanism, black hole jets are powered by the rotational energy of the compact object. In this work, we consider the possibility that the metric around black holes may not be described by the Kerr solution and we study how this changes the Blandford-Znajek model. If the Blandford-Znajek mechanism is responsible for the formation of jets, the estimate of the jet power in combination with another measurement can test the nature of black hole candidates and constrain possible deviations from the Kerr solution. However, this approach might become competitive with respect to other techniques only when it will be possible to have measurements much more precise than those available today. 
Guancheng Pei, Sourabh Nampalliwar, Cosimo Bambi, Matthew J. Middleton
gr-qc astro-ph.HE