Broad-Band Radio Spectra Variability of 550 AGN in 1997-2001
Y. Y. Kovalev, Yu A. Kovalev, N. A. Nizhelsky and A. B. Bogdantsov
Publications of the Astronomical Society of Australia
19(1) 83 - 87
Published: 30 April 2002
Results are presented of long-term monitoring at the radio telescope RATAN–600 and a model interpretation of instantaneous 1–22 GHz spectra at six frequencies for a sample of 550 compact extragalactic radio sources. The sources are selected from the Preston et al. (1985) VLBI survey and are located in the declination range from −30° to +43°. Dependence of the index of variability on frequency is analysed for different subsamples. Factors of flux density variations range from 1 to 15. A typical behaviour of spectra evolution during strong radio outbursts in various objects is recognised suggesting a common physical nature of the variability. Invoking VLBI observations in spectra–structure analysis, we find that usually more than 70% of the total emission is coming from the mas scale at frequencies higher than 5 GHz. The observed variability can be explained in the model with a relativistic jet of parsec scale in the longitudinal magnetic field or in the shock-in-jet model. Keywords: galaxies: active — galaxies: jets — BL Lacertae objects: general — quasars: general — radio continuum: galaxies
Full text doi:10.1071/AS01109
© ASA
2002
