Rapid variability of the radio flux density of 0524+034

Simultaneous observations on the RATAN-600 radio telescope at 0.97, 2.3, 3. 9, 7.7, 11.1, and 21.7 GHz during the period from January 3 to February 25, 1998, revealed variability of 0524 + 034 on time scales not exceeding 10 d ays. The variations are correlated at all frequencies where the parameters of the variability could be determined, including in the optically thick pa rt of the spectrum. The mean spectrum of the variable component was derived and is in agreement with the spectrum of a homogeneous, spherically symmet rical source. In the optically thin part of the spectrum, the spectral inde x of the variable component is alpha = -0.2, reflecting the initial energy distribution of the relativistic electrons. It is argued that the variable emission is associated with the acceleration of electrons and amplification of the magnetic field and that adiabatic expansion can be neglected. It is proposed that the observed variability is due to illumination of inhomogen eities in the jet by a shock front passing through them and that the light curve reflects the distribution and characteristic sizes of these inhomogen eities (0.14-0.5 pc for angles to the line of sight not exceeding 10 degree s, Lorentz factor gamma = 10, and adopted redshift z = 0.5). In 0524 + 034, in addition to the rapidly variable component, there are two slowly varyin g components, one of which has alpha = -0.7 in the optically thin part of t he spectrum. (C) 2000 MAIK "Nauka/Interperiodica".