Rotating non-Kerr black hole and energy extraction

Understand

The properties of the ergosphere and energy extraction by Penrose process in a rotating non-Kerr black hole are investigated.

• It is shown that the ergosphere is sensitive to the deformation parameter $\epsilon$ and the shape of the ergosphere becomes thick with increase of the parameter $\epsilon$.
• It is of interest to note that, comparing with the Kerr black hole, the deformation parameter $\epsilon$ 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.