Quiet spectra and the evolution of flares in compact extragalactic radio sources at millimeter wavelengths

The results of observations of 27 extragalactic radio sources at 12, 22, 37, and 77 GHz obtained between 1980 and 1985 are analyzed together with other data available in the literature, with emphasis on the spectra of sources at quiescent stages and of radio emission flares detected during observations. The quiescent spectra indicate that even the most compact cores in the observed sources become optically thin at frequencies of about 200 GHz in objects' rest frames. It is concluded that the energy spectral index of electrons gamma = 1.4 is universal for the cores and flare components. No significant differences are found in quiet spectra and in the flare evolution in various optical classes of radio sources.