Heterotic string plus five-brane systems with asymptotic AdS3

We present NS1+NS5-brane solutions of heterotic supergravity on curved geometries. They interpolate between a near horizon AdS(3) x X-k x T7-k region and R-1,R-1 x c(X-k) x T7-k, where X-k (with k = 3, 5, 6, 7) is a k-dimensional geometric Killing spinor manifold, c(Xk) its Ricciflat cone and T7-k a (7-k)-torus. The solutions require first-order alpha'-corrections to the field equations, and special point-like instantons play an important role, whose singular support is a calibrated submanifold wrapped by the NS5-brane. It is also possible to add a gauge anti-five-brane. We determine the super isometries of the near horizon geometry, which are supposed to appear as symmetries of the holographically dual two-dimensional conformal field theory.