Generic N=4N=4 supersymmetric hyper-Kähler sigma models in D=1D=1

We analyze the geometry of four-dimensional bosonic manifolds arising within the context of N=4N=4, D=1D=1 supersymmetry. We demonstrate that both cases of general hyper-Kähler manifolds, i.e. those with translation or rotational isometries, may be supersymmetrized in the same way. We start from a generic N=4N=4 supersymmetric three-dimensional action and perform dualization of the coupling constant, initially present in the action. As a result, we end up with explicit component actions for N=4N=4, D=1D=1 nonlinear sigma models with hyper-Kähler geometry (with both types of isometries) in the target space. In the case of hyper-Kähler geometry with translational isometry we find that the action possesses an additional hidden N=4N=4 supersymmetry, and therefore it is N=8N=8 supersymmetric one.