Rotating Non-Kerr Black Hole and Energy Extraction

The properties of the ergosphere and energy extraction by the Penrose process in a rotating non-Kerr black hole are investigated. It is shown that the ergosphere is sensitive to the deformation parameter and the shape of the ergosphere becomes thick as parameter increases. It is of interest to note that, compared with the Kerr black hole, the deformation parameter can enhance the maximum efficiency of the energy extraction process greatly. Especially for the case of a > M , the non-Kerr metric describes a superspinning compact object and the maximum efficiency can exceed 60%, while it is only 20.7% for the extremal Kerr black hole.