Search for Long-term Variability of Several Flat-Spectrum Sources at 111 MHz

Abstract

A search for long-term variability in three flat-spectrum sources has been carried out using monitoring data obtained over 5.5 years on the Large Phased Array of the Pushchino Radio Astronomy Observatory. Variability was detected at low frequencies in all three sources. A noise signal with known temperature was used to determine the relative intensity variations. The uncertainty in the estimated relative flux densities is roughly 1%, whereas the observed intensity variations exceeded 6%. The variability detected in these three sources—B0821+394, B1812+412, and B2247+140—is most likely associated with refractive interstellar scintillation.