Variability of the compact radio source at the galactic center

A variability of 20-40% is determined on time scales ranging from years to days for the compact radio source at the galactic center, in view of dual frequency radio conservations made on 25 epochs over a period of more than 3 years. The spectral epoch on each index is positive, and the spectrum appears to be flattening with time due to a steady secular increase in the mean 2695 MHz flux density. This increase suggests, for a source of constant brightness, that the source diameter has increased by about 12% in two years. An angular diameter of 0.14 arcsec is derived for the source at 2695 MHz from the modest resolution apparent at long interferometer spacings, and it is noted that these measurements are consistent with the source size increase needed to account for the steady flux density increase.