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We present a study of the multiwavelength (MW) variability of the blazar AO 0235+164 based on the radio-to-$\gamma$-ray data covering a long time period from 1997 to 2023. The radio data are represented by the 1-22 GHz measurements from the RATAN-600 radio telescope, the 5 and 8 GHz data from the RT-32 telescopes, and the 37 GHz data from the RT-22 telescope. The optical measurements in the $R$-band were collected with the 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes. Additionally we used the archive data at 230~GHz from the SMA and the $\gamma$-ray data in the 0.1-100 GeV band from the Fermi-LAT point source 4FGL-DR2 catalogue. The variability properties during four epochs containing major flares and one epoch of relatively low activity were analysed. A significant correlation ($\geq\!2\sigma$) between the radio, optical, and $\gamma$-ray bands is found for all these periods with time delays from 0 to 1.7 yrs. The relation between time delay and frequency is described by a linear law with a negative slope of -10 day/GHz. The discovered properties of MW variability for the low activity period and for flaring states suggest that the mechanisms dominating the radio-$\gamma$-ray variations are not substantially different. The detected quasi-periodic oscillations of about 6 and 2 years are tentative, as the time span of the observations includes fewer than 4 full cycles for the radio and optical data and only about 3 cycles for the Fermi-LAT data. The physical parameters of the radio jet were obtained using the Hedgehog model applied to the average radio spectrum of AO 0235+164 in the range 0.1-300 GHz. The effectiveness of replacing electrons with protons in the synchrotron radio emission of relativistic jets is shown for describing the nature of blazars and the generation of high energy neutrinos., Comment: Accepted 2024 October 30 for publication in MNRAS

Blazars are beamed active galactic nuclei known for their strong multi-wavelength variability on timescales from years down to minutes. We aim to investigate the suitability of the twisting jet model presented in previous works to explain the multi-wavelength behaviour of BL Lacertae, the prototype of one of the blazar classes. According to this model, the jet is inhomogeneous, curved, and twisting, and the long-term variability is due to changes in the Doppler factor due to variations in the orientation of the jet-emitting regions. We analysed optical data of the source obtained during monitoring campaigns organised by the Whole Earth Blazar Telescope (WEBT) in 2019-2022, together with radio data from the WEBT and other teams, and gamma-ray data from the Fermi satellite. In this period, BL Lacertae underwent an extraordinary activity phase, reaching its historical optical and gamma-ray brightness maxima. The application of the twisting jet model to the source light curves allows us to infer the wiggling motion of the optical, radio, and gamma-ray jet-emitting regions. The optical-radio correlation shows that the changes in the radio viewing angle follow those in the optical viewing angle by about 120 days, and it suggests that the jet is composed of plasma filaments, which is in agreement with some radio high-resolution observations of other sources. The gamma-ray emitting region is found to be co-spatial with the optical one, and the analysis of the gamma-optical correlation is consistent with both the geometric interpretation and a synchrotron self-Compton (SSC) origin of the high-energy photons. We propose a geometric scenario where the jet is made up of a pair of emitting plasma filaments in a sort of double-helix curved rotating structure, whose wiggling motion produces changes in the Doppler beaming and can thus explain the observed multi-wavelength long-term variability., Comment: In press for A&A

We present a study of the radio variability of bright, $S_{1.4}\geq100$ mJy, high-redshift quasars at $z\geq3$ on timescales up to 30-40 years. The study involved simultaneous RATAN-600 measurements at frequencies of 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2017-2020. In addition, data from the literature were used. We have found that the variability index, $V_S$, which quantifies the normalized difference between the maximum and minimum flux density while accounting for measurement uncertainties, ranges from 0.02 to 0.96 for the quasars. Approximately half of the objects in the sample exhibit a variability index within the range of 0.25 to 0.50, comparable to that observed in blazars at lower redshifts. The distribution of $V_S$ at 22.3 GHz is significantly different from that at 2.3-11.2 GHz, which may be attributed to the fact that a compact AGN core dominates at the source's rest frame frequencies greater than 45 GHz, leading to higher variability indices obtained at 22.3 GHz (the $V_S$ distribution peaks around 0.4) compared to the lower frequencies (the $V_S$ distribution at 2.3 and 4.7 GHz peaks around 0.1-0.2). Several source groups with distinctive variability characteristics were found using cluster analysis of quasars. We propose 7 new candidates for gigahertz peaked-spectrum (GPS) sources and 5 new megahertz peaked-spectrum (MPS) sources based on their spectrum shape and variability features. Only 6 out of 23 sources previously reported as GPS demonstrate a low variability level typical of classical GPS sources ($V_{S} < 0.25$) at 4.7-22.3 GHz. When excluding the highly variable peaked-spectrum blazars, we expect no more than 20% of the sources in the sample to be GPS candidates and no more than 10% to be MPS candidates., Comment: 56 pages, 20 Figures. Published in MDPI Galaxies

Aims. The X-ray luminous and radio-loud AGN SRGE J170245.3+130104 discovered at z $\sim$ 5.5 provides unique chances to probe the SMBH growth and evolution with powerful jets in the early Universe. Methods. We present 1.35 - 5.1 GHz Very Long Baseline Array (VLBA) results on the radio continuum emission and spectrum analysis for this quasar in a low flux density state. Results. This source is unresolved at three frequencies with the total flux densities of 8.35$\pm$0.09 mJy beam-1, 7.47$\pm$0.08 mJy beam-1, and 6.57$\pm$0.02 mJy beam-1 at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the brightness temperature is higher than 109 K. Conclusions. Compared with previous radio observations with arcsec-scale resolution, nearly all the radio emission from this source concentrates in the very central milli-arcsecond (mas) scale area. We confirm this source is a bright blazar at z > 5. This young AGN provide us the great chances to understand the first generation of strong jets in the early Universe., Comment: 5 pages, 2 figures, Accepted for publication in Astronomy & Astrophysics

Study of high-redshift radio galaxies (HzRGs) can shed light on the active galactic nuclei (AGNs) evolution in massive elliptical galaxies. The vast majority of observed high-redshift AGNs are quasars, and there are very few radio galaxies at redshifts $z>3$. We present the radio properties of 173 sources optically identified with radio galaxies at $z\geqslant1$ with flux densities $S_{1.4}\geqslant20$ mJy. Literature data were collected for compilation of broadband radio spectra, estimation of radio variability, radio luminosity, and radio loudness. Almost 60% of the galaxies have steep or ultra-steep radio spectra; 22% have flat, inverted, upturn, and complex spectral shapes, and 18% have peaked spectra (PS). The majority of the PS sources in the sample (20/31) are megahertz-peaked spectrum sources candidates, i.e. possibly very young and compact radio galaxies. The median values of the variability indices at 11 and 5 GHz are $V_{S_{11}}=0.14$ and $V_{S_{5}}=0.13$, which generally indicates a weak or moderate character of the long-term variability of the studied galaxies. The typical radio luminosity and radio loudness are $L_{5}=10^{43}$ - $10^{44}$ erg*s$^{-1}$ and $\log R=3$ - $4$ respectively. We have found less prominent features of the bright compact radio cores for our sample compared to high-redshift quasars at $z\geq3$. The variety of the obtained radio properties shows the different conditions for the formation of radio emission sources in galaxies.

We present an optical-to-radio study of the BL Lac object S4 0954+658 observations during 1998-2023. The measurements were obtained with the SAO RAS Zeiss-1000 1-m and AS-500/2 0.5-m telescopes in 2003-2023, with the RATAN-600 radio telescope at 1.25 (0.96, 1.1), 2.3, 4.7 (3.7, 3.9), 8.2 (7.7), 11.2, 22.3 (21.7) GHz in 1998-2023, with the IAA RAS RT-32 Zelenchukskaya and Badary telescopes at 5.05 and 8.63 GHz in 2020--2023, and with the RT-22 single-dish telescope of CrAO RAS at 36.8 GHz in 2009-2023. In this period the blazar had been showing extremely high broadband activity with the variability amplitude of flux densities up to 70-100% both in the optical and radio domains. In the period of 2014-2023 the blazar had been showing the historically highest activity in the radio wavelengths, and we detected multiple radio flares of varying amplitude and duration. The large flares last on average from 0.3 to 1 year at 22-36.8 GHz and slightly longer at 5-11.2 GHz. The optical flares are shorter and last 7-50 days. In the most active epoch of 2018-2023 the characteristic time scale $\tau$ of variation at 5-22 GHz is about 100 days and about 1000 days for the state with lower activity in 2009-2014. We found a general correlation between the optical, radio, and $\gamma$-ray flux variations, which suggests that we observe the same photon population from different emission regions. We estimated linear size of this region as 0.5-2 pc for different epochs. A broadband two components radio spectrum of S4 0954+658 jet was modelled by using both electrons and protons as emitting particles. It is shown that the synchrotron radio waves in this AGN may be generated by relativistic protons., Comment: Published in Astrophysical Bulletin Vol.78, N4 (2023)

We present the results of our study of cross-correlations between long-term multi-band observations of the radio variability of the blazar 3C 279. More than a decade (2008-2022) of radio data were collected at seven different frequencies ranging from 2 GHz to 230 GHz. The multi-band radio light curves show variations in flux, with the prominent flare features appearing first at higher-frequency and later in lower-frequency bands. This behavior is quantified by cross-correlation analysis, which finds that the emission at lower-frequency bands lags that at higher-frequency bands. Lag versus frequency plots are well fit by straight lines with negative slope, typically ~-30 day/GHz. We discuss these flux variations in conjunction with the evolution of bright moving knots seen in multi-epoch VLBA maps to suggest possible physical changes in the jet that can explain the observational results. Some of the variations are consistent with the predictions of shock models, while others are better explained by a changing Doppler beaming factor as the knot trajectory bends slightly, given a small viewing angle to the jet., Comment: Submitted revised version to MNRAS journal, 11 pages, 6 figures, 4 tables

Jets may have contributed to promoting the growth of seed black holes in the early Universe, and thus observations of radio-loud high-redshift quasars are crucial to understanding the growth and evolution of the early supermassive black holes. Here we report the radio properties of an X-ray bright $z=5.5$ quasar, SRGE J170245.3+130104 (J1702+1301). Our high-resolution radio images reveal the radio counterpart at the optical position of J1702+1301, while another radio component is also detected at $\sim$23.5\arcsec\ to the southwest. Our analysis suggests that this southwest component is associated with a foreground galaxy at $z\approx 0.677$, which is mixed with J1702+1301 in low-frequency low-resolution radio images. After removing the contamination from this foreground source, we recalculated the radio loudness of J1702+1301 to be $R>$1100, consistent with those of blazars. J1702+1301 exhibits a flat radio spectrum ($\alpha = -0.17 \pm 0.05$, $S \propto \nu^\alpha$) between 0.15 and 5 GHz; above 5 GHz, it shows a rising spectrum shape, and the spectral index $\alpha^{8.2}_{4.7}$ appears to be correlated with the variation of the flux density: in burst states, $\alpha^{8.2}_{4.7}$ becomes larger. J1702+1301 displays distinct radio variability on timescales from weeks to years in the source's rest frame. These radio properties, including high radio loudness, rising spectrum, and rapid variability, tend to support it as a blazar., Comment: accepted for publication in Monthly Notices of the Royal Astronomical Society

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 1.2, 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 figures

We study the radio variability of galaxies with and without sources of hydroxyl (OH) megamaser radiation based on the continuum radio measurements conducted in 2019-2022 with the radio telescope RATAN-600 at frequencies of 2.3, 4.7, 8.2, and 11.2 GHz. Presumably, radio continuum emission significantly affects the megamaser radiation brightness, therefore, such a characteristic as the variability of radio emission is important for determining the OHM galaxies parameters. With additional data from the literature, the parameters of radio variability on a time scale up to 30 years were estimated. The median values of the variability index for 48 OHM galaxies are in the range $V_{S}=0.08$-$0.17$, and for 30 galaxies without OH emission they are $V_{S}=0.08$-$0.28$. For some individual galaxies in both samples, flux density variations reach 30-50%. These sources either are commonly associated with AGNs or reveal active star formation. Generally, the variability of luminous infrared galaxies with and without OH megamaser emission is moderate and of the same order of magnitude on long time scales. From estimating the spectral energy distribution parameters in a broad frequency range (from MHz to THz), we determined the spectral index below 50 GHz and the color temperatures of dust components for megamaser and control sample galaxies. At a level of $\rho<0.05$, there are no statistically significant differences in the distribution of these parameters for the two samples, as well there are no statistically significant correlations between the dust color temperatures and the variability index or luminosity in the OH line., Comment: 15 pages, 10 Figures, and 6 Tables

Based on the two epochs EVN archive data from OH line observations of IIZw 096, we confirm that the high-resolution OH emission in this source mainly comes from two spots (OH1 and OH2) of comp D1 of this merging system. We found no significant variations in the OH line emission. The OH 1665 MHz line emission is detected at about 6 $\sigma$ level in the OH1 region by combining two epoch EVN observations. We found that the comp D1 shows the brightest CO, HCO+ line emission, as well as multi-band radio continuum emission. The environment around D1 shows no clear velocity structure associated with circular motions, making it different from most other OHMs in the literature, which might have been caused by an effect during the merger stage. Meanwhile, we found that the CO emission shows three velocity structures around D1, including the central broad FWHM region, the double peak region where the CO line profile shows two separated peaks, and the region of the high-velocity clouds where the CO line peaks at a high velocity ($\sim$ 11000 \kms). \HI in absorption also show high-velocity clouds around the D1 region, which might be due to inflows caused by the merging of two or more galaxy components. Based on the high-resolution K-band VLA and L-band VLBA observations of the radio continuum emission, we derived the brightness temperature in the range $10^{5}$ K to $10^{6}$ K, which is consistent with other starburst dominant OHM sources in the literature. The multi-band VLA observations show that the radio continuum emission of comp D might also have contributions from free-free emission, besides synchrotron emission. As a concenquence, these results support a starburst origin for the OHMs, without the presence of an AGN., Comment: 11 pages,9 figures, Accepted by A&A

We present a study of the radio continuum properties of two luminous/ultraluminous infrared galaxy samples: the OH megamaser (OHM) sample (74 objects) and the control sample (128 objects) without detected maser emission. We carried out pilot observations for 140 objects with the radio telescope RATAN-600 at 1.2, 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2019-2021. The OHM sample has two times more flat-spectrum sources (32 per cent) than the control sample. Steep radio spectra prevail in both samples. The median spectral index at 4.7 GHz $\alpha_{4.7}=-0.59$ for the OHM sample, and $\alpha_{4.7}=-0.71$ for the non-OHM galaxies. We confirm a tight correlation of the far-infrared (FIR) and radio luminosities for the OHM sample. We found correlations between isotropic OH line luminosity $L_{OH}$ and the spectral index $\alpha_{4.7}$ ($\rho$=0.26, p-val.=0.04) and between $L_{OH}$ and radio luminosity $P_{1.4}$ ($\rho$=0.35, p-val.=0.005). Reviewing subsamples of masers powered by active galactic nuclei (AGNs) and star formation revealed insignificant differences for their FIR and radio properties. Nonetheless, AGN-powered galaxies exhibit larger scatter in a range of parameters and their standard deviations. The similarities in the radio and FIR properties in the two samples are presumably caused by the presence of a significant amount of AGN sources in both samples (47 and 30 per cent in the OHM and control samples) and/or possibly by the presence of undetected OH emission sources in the control sample., Comment: 15 pages + 10 pages of online material, published 4 December 2021 in MNRAS

We report the radio continuum properties for several samples of peaked spectrum (PS) radio sources. Broadband spectra of the objects were analysed using the RATAN-600 six-frequency (1.2-22 GHz) observations and available literature data, obtained on a time scale of 20-30 years. We discuss statistical differences in radio properties for several AGN types with peaked spectra and focus on PS quasars at high redshifts ($z > 3$). We confirm that a relatively small fraction (1-2%) of bright PS sources can be considered as genuine GPSs when they have been monitored densely and for a long time. The contamination of GPS source samples by blazars is getting stronger as the redshift increases, and we confirm that it is underestimated due to lack of systematic multifrequency observations., Comment: 4 pages, 2 figures, 6th CSS/GPS sources workshop proceedings, held in May 10-14, 2021 in Torun, Poland. First published: 02 November 2021 in Astronomische Nachrichten

We present the radio properties of optically selected quasars with $z\geq3$. The complete sample consists of 102 quasars with a flux density level $S_{1.4}\geq100$ mJy in a declination range -35$^{\circ}$ $\leq$ Dec $\leq$ +49$^{\circ}$. The observations were obtained in 2017-2020 using the radio telescope RATAN-600. We measured flux densities at six frequencies 1.2, 2.3, 4.7, 8.2, 11.2, and 22 GHz quasi-simultaneously with uncertainties of 9-31 %. The detection rate is 100, 89, and 46 % at 4.7, 11.2, and 22 GHz, respectively. We have analysed the averaged radio spectra of the quasars based on the RATAN and literature data. We classify 46 % of radio spectra as peaked-spectrum, 24 % as flat, and none as ultra-steep spectra ($\alpha\leq-1.1$). The multifrequency data reveal that a peaked spectral shape (PS) is a common feature for bright high-redshift quasars. This indicates the dominance of bright compact core emission and the insignificant contribution of extended optically thin kpc-scale components in observed radio spectra. Using these new radio data, the radio loudness $\log~R$ was estimated for 71 objects with a median value of 3.5, showing that the majority of the quasars are highly radio-loud with $\log~R>2.5$. We have not found any significant correlation between $z$ and $\alpha$. Several new megahertz-peaked spectrum (MPS) and gigahertz-peaked spectrum (GPS) candidates are suggested. Further studies of their variability and additional low-frequency observations are needed to classify them precisely., Comment: accepted for publication in MNRAS, 16 pages

We report the first detection at 4.7 and 8.2 GHz with the RATAN-600 radio telescope of the source PSO J047.4478+27.2992, which has been announced as a blazar at z=6.1. The average flux density is $12\pm3$ and $8\pm4$ mJy at 4.7 and 8.2 GHz respectively, and an upper limit is estimated as 3 mJy at 11.2 GHz. The light curve at 4.7 GHz, obtained on a time-scale of four months, exhibits moderate variability of the source (fractional variability $F_{var}=0.28\pm0.02$). The new RATAN-600 measurements extend previous literature data to higher frequencies, indicating a single power-law radio spectrum with $\alpha_{0.147-8.2}$=$-0.51\pm0.1$. The monochromatic radio luminosity at 4.7 GHz $P_{\nu} \sim 2 \times 10^{27}$ W Hz$^{-1}$ is consistent with values for high-redshift quasars at $z\geq 3$., Comment: 6 pages, 5 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

We report the results of decade-long (2008-2018) $\gamma$-ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, $\it{Fermi}$ and $\it{Swift}$ data, as well as polarimetric and spectroscopic data. The X-ray and $\gamma$-ray light curves correlate well, with no delay > 3 hours, implying general co-spatiality of the emission regions. The $\gamma$-ray-optical flux-flux relation changes with activity state, ranging from a linear to a more complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz VLBA images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain $\gamma$-ray variability on very short time scales. The Mg II emission line flux in the `blue' and `red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands we find progressive delays of the most prominent light curve maxima with decreasing frequency, as expected from the frequency dependence of the $\tau=1$ surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at $\sim5$ GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet., Comment: 21 pages, 18 figures, accepted for publication in MNRAS

Gigahertz-Peaked spectrum (GPS) sources are compact active galactic nuclei, presumably young precursors of bright radio sources. The study of GPS radio properties provides information about the features of synchrotron radiation in extragalactic sources. Also in applied research GPS sources are useful as compact stationary radio sources in the sky for astrometric purposes. This paper presents the results of a multifrequency GPS study based on quasi-simultaneous measurements with the RATAN-600 radio telescope during the 2006-2017. The catalog containing spectral flux densities measured at six frequencies (1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7 GHz) have been obtained. In addition, for the analysis of radio spectra, data from the following low-frequency surveys have been used: GLEAM (GaLactic and Extragalactic All-sky Murchison widefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey. A total number of 164 GPS and candidates to GPS have been identified (17 of them are new discoveries), which makes up a small fraction of GPS in the initial sample of bright AGNs, about 2%. The physical properties and formation conditions of synchrotron radiation is found to be quite different in GPS of different AGN types. The deficit of distant GPS ($z > 2$) with low maximum frequencies (less than 1 GHz) is confirmed. The existing 'size - peak frequency' anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift., Comment: 30 pages, including 11 pages of radio spectra as the supplementary material

We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi ($\gamma$ rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented $\gamma$-ray flaring activity was observed during 2016 November-2017 February, with four major outbursts. A peak flux of (2158 $\pm$ 63)$\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$, corresponding to a luminosity of (2.2 $\pm$ 0.1)$\times$10$^{50}$ erg s$^{-1}$, was reached on 2016 December 28. These four $\gamma$-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and $\gamma$-ray activity is found. The $\gamma$-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This $\gamma$-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission., Comment: 24 pages, 18 figures, and 4 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

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 Nachrichten

Observations at 37 GHz, performed at Mets\"ahovi Radio Observatory, are presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1 (NLS1) galaxies, together with additional lower and higher frequency radio data from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most of the data have been gathered between February 2012 and April 2015 but for some sources even longer lightcurves exist. The detection rate at 37 GHz is around 19%, comparable to other populations of active galactic nuclei presumed to be faint at radio frequencies, such as BL Lac objects. Variability and spectral indices are determined for sources with enough detections. Based on the radio data, many NLS1 galaxies show a blazar-like radio spectra exhibiting significant variability. The spectra at a given time are often inverted or convex. The source of the high-frequency radio emission in NLS1 galaxies, detected at 37 GHz, is most probably a relativistic jet rather than star formation. Jets in NLS1 galaxies are therefore expected to be a much more common phenomenon than earlier assumed., Comment: Accepted for publication in A&A. Table of 37 GHz data will be available at the CDS soon

We study the synchrotron component of the spectral energy distribution (SED) on the sample of 877 blazars using the ASDC SED Builder Tool with available broadband data from the literature. Our sample includes 423 flat-spectrum radio sources (FSRQs), 361 BL Lac objects and candidates, and 93 blazars of uncertain type. We have made an estimation of the synchrotron peak frequency ($\nu_{peak}^{s}$) for the 875 objects and further classified them as high, intermediate and low synchrotron peaked sources (HSPs/ISPs/LSPs). There are 42 HSPs with $\nu_{peak}^{s} > 10^{16.5}$ Hz, 222 ISPs with $10^{14.5} < \nu_{peak}^{s} < 10^{16.5}$ Hz, and 611 LSPs with $\nu_{peak}^{s} < 10^{14.5}$ Hz in our sample. We have calculated an average value of $\nu_{peak}^{s}$ to be $10^{13.4 \pm 1.0}$ Hz for FSRQs and $10^{14.6 \pm 1.4}$ Hz for BL Lacs. We found out that $\nu_{peak}^{s}$ and the flux density at 4.8 GHz have a different distribution (as indicated by Kolmogorov-Smirnov test at significance level 0.05) for the FSRQ and BL Lac blazars, and for the RBL and XBL types of BL Lacs. Distribution of $\nu_{peak}^{s}$ values is broader for BL Lacs, than for FSRQs. There are no ultra-high energy peaked objects (with $\nu_{peak}^{s} > 10^{19}$ Hz) in our BL Lac sample according to our estimations. The significant part of FSRQs (41%) and small part of BL Lacs (9%) in our sample could be considered as candidates to the very-low synchrotron peaked blazars (with $\nu_{peak}^{s} < 10^{13}$ Hz). Our foundations confirm results of the previous studies made on samples with significantly smaller number of objects., Comment: 12 pages, 6 figures. Will appear in Astrophysical Bulletin, Volume 70, Issue 3, 2015

We have made an estimation of the synchrotron peak frequency ($\nu_{peak}^{s}$) for six very low synchrotron peaked (VLSP) blazars. These objects were selected as VLSP candidates (with the $\nu_{peak}^{s} \leq 10^{13}$ Hz) from the archival data. We have build spectral energy distribution using quasi-simultaneous observations at the Zeiss-1000 and RATAN-600 telescopes of the Special astrophysical observatory of RAS and made an estimation of the $\nu_{peak}^{s}$. We confirmed classification as a VLSP for two sources ([HB89] 1308+326 and 3C 345), for four other blazars we have calculated $\nu_{peak}^{s}>10^{13}$ Hz., Comment: 7 pages; published in Astrophysical Bulletin, Volume 70, Issue 3, 2015

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 MNRAS

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 one percent of known AGNs. They belong to the blazar population and differ from other blazars 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 minutes 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 for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600.

We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by Fermi-LAT, whereas ~40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-mm spectral slope of blazars is quite flat up to ~70GHz, above which it steepens to <\alpha>~-0.65. BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (\nupS) in the SED of FSRQs is the same in all the blazar samples with <\nupS>=10^13.1 Hz, while the mean inverse-Compton peak frequency, <\nupIC>, ranges from 10^21 to 10^22 Hz. The distributions of \nupS and of \nupIC of BL Lacs are much broader and are shifted to higher energies than those of FSRQs and strongly depend on the selection method. The Compton dominance of blazars ranges from ~0.2 to ~100, with only FSRQs reaching values >3. Its distribution is broad and depends strongly on the selection method, with gamma-ray selected blazars peaking at ~7 or more, and radio-selected blazars at values ~1, thus implying that the assumption that the blazar power is dominated by high-energy emission is a selection effect. Simple SSC models cannot explain the SEDs of most of the gamma-ray detected blazars in all samples. The SED of the blazars that were not detected by Fermi-LAT may instead be consistent with SSC emission. Our data challenge the correlation between bolometric luminosity and \nupS predicted by the blazar sequence., Comment: Version accepted by A&A. Joint Planck, Swift, and Fermi collaborations paper

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper, physical modelling of the synchrotron bump using multiplecomponents. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission., Comment: High-resolution figures will be posted at http://www.rssd.esa.int (TBC). Accepted version updated, Published version updated

Planck's all sky surveys at 30-857 GHz provide an unprecedented opportunity to follow the radio spectra of a large sample of extragalactic sources to frequencies 2-20 times higher than allowed by past, large area, ground-based surveys. We combine the results of the Planck Early Release Compact Source Catalog (ERCSC) with quasi-simultaneous ground-based observations, as well as archival data, at frequencies below or overlapping Planck frequency bands, to validate the astrometry and photometry of the ERCSC radio sources and study the spectral features shown in this new frequency window opened by Planck. The ERCSC source positions and flux density scales are found to be consistent with the ground-based observations. We present and discuss the spectral energy distributions (SEDs) of a sample of "extreme" radio sources to illustrate the richness of the ERCSC for the study of extragalactic radio sources. Variability is found to play a role in the unusual spectral features of some of these sources., Comment: Revised to accommodate referee's comments. Changes made to sections 5.1 and 5.4. No change in figures or scientific conclusions

The IX Russian-Finnish Symposium on Radio Astronomy was held in Special astrophysical observatory RAS in Nizhnij Arkhyz, Russia on 15-20 October 2006. It was dedicated to the two-side collaboration in the field of multi-wavelength investigations of solar radio emission, studies of polar regions of the Sun, studies of stellar activity, AGNs, quasars and BL Lac objects in radio bands from millimeter to decimetre wavelengths with RATAN-600, Metsahovi 14m, RT32m radio telescope and VLBI systems. Here abstracts of all forty papers are given. The Web-site of the Symposium is http://cats.sao.ru/~satr/RFSymp/ ., Comment: 41 pages, abstracts of the Symposium papers

We present new RATAN-600 data on the synchrotron Galaxy radiation at the PLANCK Mission and WMAP frequencies at high Galactic latitudes upto l=3000. The difference between the standard synchrotron template (l<50) of the WMAP group and RATAN-600 data was detected with the strong synchrotron ``longitude quadrant asymmetry''. It may change the WMAP estimates of z_{reheating} from low l polarization data. The polarized synchrotron noise for very deep observations (<< 1 microK) at the PLANCK HFI was not detected at l>200 scales. ``Sakharov Oscillations'' in the E-mode (500

We present observational results for extragalactic radio sources with milliarcsecond components, obtained with the 600 meter ring radio telescope RATAN-600 from 1st to 22nd December, 1997. For each source, a six frequency broad band radio spectrum was obtained by observing simultaneously with an accuracy up to a minute at 1.4, 2.7, 3.9, 7.7, 13 and 31 cm. The observed list is selected from Preston et al. (1985) VLBI survey and contains all the sources in the declinations between -30deg and +43deg with a correlated flux density exceeding 0.1 Jy at 13 cm. The sample includes the majority of sources to be studied in the current VSOP survey and the future RadioAstron Space VLBI mission., Comment: 26 pages, 4 figures, 5 tables, published in the A&AS; figure 4 with the broad-band spectra plots is included in the preprint; tables 1 and 5, in electronic form, as well as the ReadMe file can be extracted from the preprint source

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., Comment: 4 pages, PDF

We present optical identifications and radio spectra for ten radio sources from two flux-density-complete samples. Radio variability characteristics are presented for four objects. The observations were obtained on the RATAN-600 radio telescope at 0.97-21.7 GHz and the 2.1 m telescope of the Haro Observatory in Cananea, Mexico at 4200-9000 =C5. Among the ten objects studied, three are quasars, four are BL Lac objects, two are radio galaxies, and one is a Sy 1 galaxy. Two of the sources identified with BL Lac objects, 0509 + 0541 and 0527 + 0331, show rapid variability on time scales of 7-50 days., Comment: 6 pages, PDF