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EXTRAGALACTIC SOURCE VARIABILITY STUDIES OF COMPLETE SAMPLES WITH RATAN-600
A.G. Gorshkov1 , M.G. Mingaliev
1 2

Sternb erg Astronomical Institute, Moscow State University, Universitetskij pr., 13, Moscow, 119992, Russia 2 Sp ecial Astrophysical Observatory of RAS, Nizhnij Arkhyz, 369167, Russia algor@sai.msu.ru

We present preliminary results of the study and analysis of complete and limited in flux density source samples from the Zelenchuk and MGB surveys carried out with the RATAN-600 radio telescop e. This work pursues two the main aims: · Investigation of general statistical characteristics of a discrete source sample; · Investigation of variability pro cesses in discrete sources in a wide range of wavelengths. That assumes a study of the amplitude and frequency characteristics of variability on all time scales from several years to several days. The following results of this investigation have b een revealed (or confirmed): 1. The long-term variability with a time-scale more than several years. Our observations have allowed to trace a complete evolution cycle of the isolated flare in a numb er of sources from its o ccurrence b efore decay and to sp ecify its amplitude and frequency characteristics. There is no plateau at the maximum of a flare, a flare increase and decay are well describ ed by a exp onential temp oral law. Such a form of flare is not describ ed by any mo del. 2. The variability with a time-scale ab out tens of days. We consider the variability with a week time scale as an imp ortant result of our investigation. It is a new typ e of the variability and, as it was found out, it is widespread enough. Approximately 10% of sources with flat sp ectra have a similar variability. The variability often has a cyclic nature and, basically, is exp osed at frequencies b elow 10 GHz. 3. The existence of variability with a time-scale ab out four days for all compact radio sources. We are sure that the given typ e of variability is not a prop erty of a radio source, but a result of radiation propagation in inhomogeneous interstellar medium.