V. K. Konnikova

Spectra, Optical Identifications, and Statistics of a Complete Sample of Radio Sources at Declinations 10 ◦ -12 ◦ 30

The results of 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz observations of a complete sample of radio sources obtained on the RATAN-600 radio telescope are presented. The sample is comprised of sources from the 4.85-GHz MGB survey, and contains all sources at declinations 10°–12°30′ (J2000) with Galactic latitudes |b|>15° and flux densities S4.85>200 mJy. Optical identifications have been obtained for about 86% of the radio sources with flat spectra and 59% of those with steep spectra. The spectra of the flat-spectrum sources have been decomposed into extended and compact components.

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 days. The variations are correlated at all frequencies where the parameters of the variability could be determined, including in the optically thick part of the spectrum. The mean spectrum of the variable component was derived and is in agreement with the spectrum of a homogeneous, spherically symmetrical source. In the optically thin part of the spectrum, the spectral index of the variable component is α=−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 inhomogeneities in the jet by a shock front passing through them and that the light curve reflects the distribution and characteristic sizes of these inhomogeneities (0.14–0.5 pc for angles to the line of sight not exceeding 10°, Lorentz factor γ=10, and adopted redshift z=0.5). In 0524+034, in addition to the rapidly variable component, there are two slowly varying components, one of which has α=−0.7 in the optically thin part of the spectrum.

Spectral Studies with the Special Astrophysical Observatory 6 m and RATAN-600 Telescopes

We present optical identifications, classifications, and radio spectra for 19 radio sources from a complete sample in flux density with declinations 10°–12°30′ (J2000) obtained with the 6-m optical telescope (4000–9000 Å) and RATAN-600 radio telescope (0.97–21.7 GHz) of the Special Astrophysical Observatory. Twelve objects with redshifts from 0.573 to 2.694 have been classiffied as quasars, and two objects with featureless spectra as BL Lac objects. Four objects are emission-line radio galaxies with redshifts from 0.204 to 0.311 (one also displaying absorption lines), and one object is an absorption-line galaxy with a redshift of 0.214. Radio flux densities have been obtained at six frequencies for all the sources except for two extended objects. The radio spectra of five of the sources can be separated into extended and compact components. Three objects display substantial rapid (on time scales from several days to several weeks) and long-term variability of their flux densities.

Radio and optical spectral studies of radio sources

Optical identifications and an analysis of the radio spectra of eight radio sources from a flux-density-complete sample at declinations 4°–6° (B 1950) are presented. The observations were carried out at 4000–9000 Å on the 6-m telescope of the Special Astrophysical Observatory and at 0.97–21.7 GHz on the RATAN-600 telescope. Five of the eight sources are quasars and three are emission-line radio galaxies.

Variability Observations of a Complete Sample of Flat-Spectrum Radio Sources: Preliminary Results

This report presents preliminary results of daily observations, over 60and 100 days, of a complete, flux-limited sample of radio sources with flat spectra. The existence of flicker up to 21.7 GHz was confirmed, for sources with flat spectra, on a time-scale of 4 days. A model explaining the flux density variations of the unique radio source 0524+034, on long and short time-scales, by an intrinsic mechanism is proposed.

Radio and optical spectra of objects from three complete samples of radio sources

We present classifications, optical identifications, and radio spectra for 19 radio sources from three complete samples, with declinations 4°–6° (B1950, S3.9 GHz > 200 mJy), 10°–12°30′ (J2000, S4.85 GHz > 200 mJy), and 74°–75° (J2000, S4.85 GHz > 100 mJy). We also present corresponding information for the radio source J0527+0331. The right ascensions are 0–24h and the Galactic latitudes |b| > 15° for all the samples. Our observations were obtained with the 6 m telescope from the Special Astrophysical Observatory in the range 4000–9000 Å or 4000–7500 Å and the RATAN-600 radio telescope at frequencies in the range 0.97–21.7 GHz. We obtained flux densities for the radio sources and optical spectra for their optical counterparts. Nine objects were classified as quasars with redshifts from z = 1.029 to 3.212; nine objects are emission-line galaxies with redshifts from 0.172 to 0.546, and one is a galaxy with burstlike star formation at z = 0.156, and one is a BL Lac object with z = 0.509. The spectra of five radio sources were decomposed into extended and compact components. The radio source J0527+0331, identified with a BL Lac object, displays significant variations of time scales from several days to several years. Data on flux variations are presented for 11 radio sources, as well as their spectra at several epochs.

Analysis of instantaneous spectra of a complete sample of flat-spectrum radio sources

The results of observations of a complete sample of radio sources with spectral indices α>−0.5 (S∝vα) are presented. The sample was selected from the Zelenchuk Survey at 3.9 GHz and contains all sources with declinations 4°–6°, Galactic latitudes |b|>10°, and 3.9-GHz fluxes >200 mJy. Spectra at 0.97–21.7 GHz were obtained for all 69 sample sources. The spectra were classified, and a correlation between variability amplitude and spectrum shape was found. The spectra were separated into extended and compact components. The distribution of spectral indices α for the extended components coincides with the distribution for sources with power-law spectra. The correlation between the luminosity and frequency of the peak flux density is confirmed. This correlation is due to the fact that the distribution of source linear dimensions does not depend on luminosity.

Classification of Optical Identifications of Radio Sources from Complete Samples

Classifications of the optical counterparts and radio spectra of nine radio sources are presented. The observations were carried out using the 2.1-m optical telescope in Cananea (Mexico) at 4200–9000 Å and the RATAN-600 radio telescope at 0.97–21.7 GHz. Five objects have been classified as quasars (three have redshifts z>2), two as BL Lac objects, one as an elliptical galaxy, and one as an absorption-line galaxy.

Optical Spectra of Four Objects Identified with Variable Radio Sources

We obtained optical spectra of four objects identified with variable radio sources. Three objects (0029+0554, 0400+0550, 2245+0500) were found to be quasars with redshifts of 1.314, 0.761, and 1.091. One object (2349+0534) has a continuum spectrum characteristic of BL Lac objects. We analyze spectra of the radio sources in the range 0.97–21.7 GHz for the epoch 1997 and in the range 3.9–11.1 GHz for the epoch 1990, as well as the pattern of variability of their flux densities on time scales of 1.5 and 7 years.

Instantaneous spectra for a complete sample of radio sources in the declination range 74°-75°

We present the results of observations of a complete sample of radio sources with the RATAN-600 radio telescope at 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz. The sample was extracted from the GB6 catalog at 4.85 GHz, and contains all the sources at declinations 74°–75° (J2000) with flux densities S4.85 > 100 mJy. We have obtained optical identifications for 67% of the radio sources with flat spectra and 30% of those with steep spectra.