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Paper: VLBI Observations of the Galactic Center Source SGR A* at 86 GHz and 215 GHz
Volume: 186, The Central Parsecs of the Galaxy
Page: 89
Authors: Krichbaum, T. P.; Witzel, A.; Zensus, J. A.
Abstract: We (for collaborators see acknowledgement) summarize previous VLBI observations of Sgr A* at millimeter wavelengths and present new results from VLBI observations at 86 GHz and at 215 GHz. At 86 GHz the measured closure phase is close to zero, consistent with a point-like or symmetric structure of 190 +/- 30 μas size. At 215 GHz we have (for the first time) detected Sgr A* with a signal-to-noise ratio of 6. This yields a tentative size estimate of 50 <= &thetas; <= 190 μas, which is larger than the scattering size of 20 μas at this frequency. The intrinsic size of Sgr A* thus appears to be a few up to a few ten Schwarzschild radii (for a 2.6 cdot 106 M solar black hole).
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