I have just read (in the black holes chapter 14 on p244 of this book Ref.1) that in string theory, when one adds an (electric?) charge $Q$ to a static black hole, one can arrive at an exotic supersymmetric black hole. This sentence is not explained further and there are several (I think related enough) things I dont understand about it, which can be summerized under the question what really is an exotic suppersymmetric black hole?
First, how exactly does the addition of a charge (if it is not outright a supercharge) lead to supersymmetry?
Second, what is meant by an exotic black hole, conversely to for example an extremal black hole that has just the maximum charge allowed given its mass?
Third, what does it mean for a black hole to be supersymmetric anyway?
- D. McMohan, String Theory Demystified, McGraw-Hill, 2009