ABSTRACT

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ABSTRACT: We present recent results from 86 and 215 GHz VLBI observations of the compact radio source at the Galactic Center. At 86 GHz we find a size consistent or only marginal larger than the expected scattering size at this frequency. A zero closure phase indicates a point-like or symmetrical structrue. At 215 GHz we have detected for the first time Sgr A* with VLBI. This detection (on the baseline Pico Veleta - Plateau de Bure) yields a tentative size estimate, which depends on the assumption of the total (zero-spacing) flux and the antenna calibration. We find evidence that the size could be larger than the scattering size at 215 GHz (20 micro-arcseconds). If confirmed by follow up observations, the intrinisc structure of Sgr A* could be studied with a spatial resolution of only a few 10 Schwarzschild radii.