Kaonic atoms and in-medium $K^-N$ amplitudes

Recent work on the connection between in-medium subthreshold $K^-N$ amplitudes and kaonic atom potentials is updated by using a next to leading order chirally motivated coupled channel separable interaction model that reproduces $\bar KN$ observables at low energies, including the very recent SIDDHARTA results for the atomic $K^-$-hydrogen $1s$ level shift and width. The corresponding $K^-$-nucleus potential is evaluated self-consistently within a single-nucleon approach and is critically reviewed with respect to empirical features of phenomenological optical potentials. The need to supplement the single-nucleon based approach with multi-nucleon interactions is demonstrated by showing that additional empirical absorptive and dispersive terms, beyond the reach of chirally motivated $K^-$-nucleus potentials, are required in order to achieve good agreement with the bulk of the data on kaonic atoms.