http://arxiv.org/abs/1509.01941
Near-infrared observations of stellar orbits at the Galactic Center provide conclusive evidence for a massive black hole associated with the compact radio source Sgr A*. The astrometric reference frame for these observations is tied to a set of red giant stars, which are also detectable at radio wavelengths through SiO maser emission in their envelopes. We have improved the precision and long-term stability of this reference frame, in which Sgr A* is localized to within a factor 5 better than previously: ~0.17 mas in position (in 2009) and ~0.07 mas/yr in velocity. This improvement is the result of modeling and correcting optical distortion in the VLT/NACO imager to a sub-mas level and including new infrared and radio measurements, which now both span more than a decade in time. A further improvement will follow future observations and facilitate the detection of relativistic orbital effects.
P. Plewa, S. Gillessen, F. Eisenhauer, et. al.
Tue, 8 Sep 15
5/69
Comments: 12 pages, 8 figures, 5 tables. MNRAS in press
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