O(6,22) BPS configurations of the heterotic string.

We present a static multi-center magnetic solution of toroidally compactified heterotic string theory, which is T-duality covariant. The space-time geometry depends on the mass M and on the O(6,22)-norm N of the magnetic charges. For different range of parameters (M,N)-solution includes 1) two independent positive parameters extremal magnetic black holes with non-singular geometry in stringy frame (a = 1 black holes included), 2) a = √ 3 extremal black holes, 3) singular massive and massless magnetic white holes (repulsons). The electric multi-center solution is also given in an O(6,22)-symmetric form. 1 Permanent address: Institut für Physik, Humboldt-Universität, 10115 Berlin, Germany; E-mail: [email protected] 2 E-mail: [email protected]