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EXTRAGALACTIC SOURCE VARIABILITY STUDIES OF
COMPLETE SAMPLES WITH RATAN­600
A.G. Gorshkov 1 , M.G. Mingaliev 2
1 Sternberg Astronomical Institute, Moscow State University, Universitetskij pr., 13,
Moscow, 119992, Russia
2 Special 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
RATAN­600 radio telescope.
This work pursues two the main aims:
. Investigation of general statistical characteristics of a discrete source sample;
. Investigation of variability processes 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 been revealed (or confirmed):
1. The long­term variability with a time­scale more than several years. Our observations
have allowed to trace a complete evolution cycle of the isolated flare in a number of
sources from its occurrence before decay and to specify its amplitude and frequency
characteristics. There is no plateau at the maximum of a flare, a flare increase and
decay are well described by a exponential temporal law. Such a form of flare is not
described by any model.
2. The variability with a time­scale about tens of days. We consider the variability with
a week time scale as an important result of our investigation. It is a new type of the
variability and, as it was found out, it is widespread enough. Approximately 10% of
sources with flat spectra have a similar variability. The variability often has a cyclic
nature and, basically, is exposed at frequencies below 10 GHz.
3. The existence of variability with a time­scale about four days for all compact radio
sources. We are sure that the given type of variability is not a property of a radio
source, but a result of radiation propagation in inhomogeneous interstellar medium.