BOGOMOLNYI BOUNDS AND KILLING SPINORS IN D=3 SUPERGRAVITY

We discuss the connection between the construction of Bogomol'nyi boun ds and equations in three dimensional gravitational theories and the e xistence of an underlying N = 2 local supersymmetric structure. We sho w that, apart from matter self duality equations, a first order equati on for the gravitational field (whose consistency condition gives the Einstein equation) can be written as a consequence of the local supers ymmetry, Its solvability makes possible the evasion of the no-go scena rio for the construction of Killing spinors in asymptotically conical spacetimes. In particular we show that the existence of non-trivial su percovariantly constant spinors is guaranteed whenever field configura tions saturate the topological bound.