408 MHz variability of complete samples of radio sources.

The authors present two complete samples of low frequency variable sources, obtained by comparing the B2 and B3 surveys. The first sample consists of 77 sources with two flux density measurements separated by ≡10 years; the second one consists of 26 sources with two measurements separated by ≡10 - 12 months. The authors compare the frequency of occurrence of the low frequency variability phenomenon in the two samples. Optical identifications of the variable sources give high percentage of blue objects and empty fields. The distribution of the percentage of variables versus the galactic latitude suggests that the variability could be due to propagation effects through the interstellar medium.