Quantum N=2 supersymmetric black holes in the S-T model

We consider axion-free quantum corrected black hole solutions in the context of the heterotic S-T model with half the N = 2, D = 4 supersymmetries unbroken. We express the perturbatively corrected entropy in terms of the electric and magnetic charges in such a way, that target-space duality invariance is manifest, We also discuss the microscopic origin of particular quantum black hole configurations, We propose a microscopic interpretation in terms of a gas of closed membranes for the instanton corrections to the entropy. (C) 1997 Elsevier Science B.V.