Radio Variability of Sgr A* at Centimeter Wavelengths

Abstract

Results of two years of continuous monitoring of flux density variations at 8.3 and 2.3 GHz of the Galactic Center super-massive black hole candidate Sgr A* are reported. The average RMS modulation indices are 6% and 2.5% at 8.3 & 2.3 GHz respectively. There is a certain degree of correlation between both frequencies. The timescale of variability at 8.3 & 2.3 GHz is between 50 and 200 days. We cannot confirm a lambda^2 dependence of the timescale. At 2.3 GHz a quasi-periodic behaviour with a period of 57 days was discovered which is reminiscent to, though longer than, those found in some compact extragalactic radio sources.