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G.C. Bower (NRAO --- Socorro), H. Falcke (MPIfR --- Bonn), D.C. Backer (UC Berkeley Astronomy)
We present the results of VLA and ATCA monitoring of the circular polarization in the Galactic Center black hole candidate, Sagittarius A*. The high fraction of circular polarization (~0.5%) is unusual given the very low linear polarization (<0.1%) present in the source. Analysis of archival VLA data indicates that the 4.8 GHz fractional circular polarization was stable over the past two decades despite a factor-of-two change in the total intensity. Recent monitoring with the VLA and ATCA indicate that there is significant variability on timescales of days to weeks. The degree of variability and the fraction of circular polarization increases with frequency over the range 1.4 to 15 GHz. We discuss the impact of these results on models for Sgr A*. We also consider whether low luminosity objects display common polarization properties distinct from those of high luminosity objects.
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