RADIO VARIABILITY IN THE NUCLEI OF DOUBLE RADIO GALAXIES AND QUASARS

A search for radio variability in the central components of eight extended double radio sources has been made with the Cambridge 5-km telescope. The three radio galaxies observed all showed variability, whereas the central components of the five quasars remained constant. The strongest variations are observed in 3C111, for which extensive data exist. These variations violate the conventional brightness temperature limit if the source is static, but they are consistent with a relativistic jet with Y = 2, a value which is also admitted by the statistical properties of central components of double sources. © Royal Astronomical Society.