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.

5 pages, 3 figures, (PASP)Latex, in: "The Central Parsecs of the Galaxy", eds. H. Falcke, A. Cotera, W.J. Duschl, F. Melia, M.J. Rieke, ASP Conf. Series, Vol. 186, p. 113, also available at http://www.mpifr-bonn.mpg.de/staff/hfalcke/publications.html#gc98p1