The observed radio/gamma-ray emission correlation for blazars with the Fermi-LAT and the RATAN-600 data

We study the correlation between gamma-ray and radio band radiation for 123 blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data obtained at the same period of time (within a few months). We found an apparent positive correlation for BL Lac and flat-spectrum radio quasar (FSRQ) sources from our sample through testing the value of the Pearson product-moment correlation coefficient. The BL Lac objects show higher values of the correlation coefficient than FSRQs at all frequencies, except 21.7 GHz, and at all bands, except $10-100$ GeV, typically at high confidence level (> 99%). At higher gamma-ray energies the correlation weakens and even becomes negative for BL Lacs and FSRQs. For BL Lac blazars, the correlation of the fluxes appeared to be more sensitive to the considered gamma-ray energy band, than to the frequency, while for FSRQ sources the correlation changed notably both with the considered radio frequency and gamma-ray energy band. We used a data randomization method to quantify the significance of the computed correlation coefficients. We find that the statistical significance of the correlations we obtained between the flux densities at all frequencies and the photon flux in all gamma-ray bands below 3 GeV is high for BL Lacs (chance probability $\sim 10^{-3} - 10^{-7}$). The correlation coefficient is high and significant for the $0.1-0.3$ GeV band and low and insignificant for the $10-100$ GeV band for both types of blazars for all considered frequencies.Comment: 14 pages, 5 tables, 8 figures, accepted to MNRA

Simultaneous spectra and radio properties of BL Lac's

We present the results of nine years of the blazar observing programme at the RATAN-600 radio telescope (2005-2014). The data were obtained at six frequency bands (1.1, 2.3, 4.8, 7.7, 11.2, 21.7 GHz) for 290 blazars, mostly BL Lacs. In addition, we used data at 37 GHz obtained quasi-simultaneously with the Metsahovi radio observatory for some sources. The sample includes blazars of three types: high-synchrotron peaked (HSP), low-synchrotron peaked (LSP), and intermediate-synchrotron peaked (ISP). We present several epochs of flux density measurements, simultaneous radio spectra, spectral indices and properties of their variability. The analysis of the radio properties of different classes of blazars showed that LSP and HSP BL Lac blazars are quite different objects on average. LSPs have higher flux densities, flatter spectra and their variability increases as higher frequencies are considered. On the other hand, HSPs are very faint in radio domain, tend to have steep low frequency spectra, and they are less variable than LSPs at all frequencies. Another result is spectral flattening above 7.7 GHz detected in HSPs, while an average LSP spectrum typically remains flat at both the low and high frequency ranges we considered.Comment: 14 pages, 6 figures. Accepted for publication in Astronomische Nachrichte

Flux-density variability of the blazar S5 1803+784 (J1800+7828) on a timescale of a month

The variability of the blazar S5 1803+784 (J1800+7828) on a timescale of a month is analyzed using daily RATAN-600 observations in 2009 (a total of 154 observations) at five frequences from 2.3 to 21.7 GHz. Cyclic variability of the flux density was detected at 7.7, 11.1, and 21.7 GHz on a timescale of 34-35 days, with modulation indices of 2.1, 3.6, and 6.6%, respectively. Characteristic time scales are derived from the light curves and the structure and autocorrelation functions. The spectrum of the variable component is rising, with spectral index α ≈ 1.3. The delays of the light-curve maxima between 21.7-11.1 and 11.1-7.7 GHz are three to four days. The integrated spectra for different light-curve phases indicate that the maximum shifts toward lower frequencies as the flux density passes through the maximum. Our results suggest that the variability can be explained mainly by non-stationary processes in the radio source itself, due to the propagation of shocks in the jet. © 2013 Pleiades Publishing, Ltd

Long-term and rapid variability of the radio source J1603+1105

© 2017, Pleiades Publishing, Ltd. We present the long-term light curve of the radio source J1603+1105 and results of the study of its variability on timescales from several days to several weeks. From 2007, a flare with the maximum in 2010 was observed for the object that earlier showed no significant variations of flux density. Three flares with a successively decreasing amplitude were detected at an active phase in the long-term light curve. The characteristic time of the first one was 2.5 yrs. In five sets of daily observations of 95 to 120 days, the flux density variability on scales from 9 to 32 days in 2011, 2012, 2015, and 2016 was detected; in 2015 it was detected at three frequencies simultaneously. In 2011, the variability was found at a single frequency of 4.8 GHz; in 2012—at two frequencies, 4.8 and 7.7 GHz; in 2015—at 4.6, 8.2, and 11.2 GHz.We present instant spectra of the source at different flare phases showing that the dynamics of the flare development is consistent with the model, in which the variability is the result of the shock wave evolution in the radio source jet

RATAN-600 multi-frequency data for the BL Lacertae objects

We present a new catalogue of the RATAN-600 multi-frequency measurements for BL Lac objects. The purpose of this catalogue is to compile the BL Lac multi-frequency data that is acquired with the RATAN-600 simultaneously at several frequencies. The BL Lac objects emit a strongly variable and polarized non-thermal radiation across the entire electromagnetic spectrum from radio to gamma rays and represent about 1% of known AGNs. They belong to the blazar population and differ from other blazars&#39; featureless optical spectrum, which sometimes have absorption lines, or have weak and narrow emission lines. One of the most effective ways of studying the physics of BL Lacs is the use of simultaneous multi-frequency data. The multi-frequency broadband radio spectrum was obtained simultaneously with an accuracy of up to 1-2 min for four to six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The catalogue is based on the RATAN-600 observations and on the data from: equatorial coordinate and redshift, R-band magnitude, synchrotron peak frequency, SED classes, and object type literature. The present version of the catalogue contains RATAN-600 flux densities measurements over nine years (2006-2014), radio spectra at different epochs, and their parameters of the catalogue for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600.</p

Spectra and variability of a sample of polar sources

The results of 154 daily observations of 33 sources in the declination interval 70°-84.° 5 (J 2000), made in 2009, are reported. Four objects are found to exhibit variations with typical time scales ranging from 8 to 35 days and modulation indices 2.1-5.6%. The spectra of the variable components are obtained. The same sources were observed again after six months, in 2010, for a duration of up to 55 days. The 11.1 GHz flux densities of one third of the sources varied by more than 10% between the two data sets. © 2013 Pleiades Publishing, Ltd

Multifrequency quasi-simultaneous observations of six low-synchrotron peaked blazars

© Pleiades Publishing, Ltd., 2015. We made an estimation of the synchrotron peak frequency (νspeak) of the spectral energy distribution (SED) for six blazars. These objects were selected as very-low-synchrotron peaked (VLSP) blazar candidates (with νspeak ≤ 1013 Hz).We have built the SED of the studied objects using quasi-simultaneous observations on the SAO RAS Zeiss-1000 and RATAN-600 telescopes and made an estimation of the synchrotron peak frequency. As a result, three sources (PKS0446+11, [HB89] 1308+326, and 3C345) were confirmed as VLSP, for the three remaining blazars the calculations have shown νspeak > 1013 Hz

The RATAN-600 multi-frequency catalogue of blazars -- BLcat

In this paper we present the RATAN-600 multi-frequency catalogue of blazars, an updated version of the BLcat: the RATAN-600 multi-frequency catalogue of BL Lacertae objects. The main novelty in the catalogue is an extension of the sample with flat-spectrum radio quasars (FSRQs), thus currently it contains more than 1700 blazars of different types. The main feature of the BLcat is a compilation of radio continuum data for blazars based on the RATAN-600 quasi-simultaneous measurements at frequencies of 1.1, 2.3, 4.7, 7.7/8.2, 11.2, and 21.7/22.3 GHz. We additionally supplement the catalogue with the radio data from external sources to provide an opportunity to more complete study of radio spectra and radio light curves. For the convenience of users, we developed tools to calculate the spectral index, variability index, and radio luminosity. We briefly describe basic radio properties of blazar subsamples of the catalogue: spectral classification, spectral indices, flux density variability, and radio luminosity.Comment: 9 pages, 8 figure