We present a study of the radio and optical properties of the high-frequency peaker (HFP) blazar PKS 1614 + 051 at z=3.21 based on the data covering the time period of 1997–2024. The radio data are represented by the instantaneous 1–22 GHz measurements from the SAO RAS RATAN-600 radio telescope, the 5 and 8 GHz data from the IAA RAS RT-32 telescopes, and the 37 GHz data from the RT-22 telescope of CrAO RAS. The optical measurements in the R band were collected with the SAO RAS 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes, and the ZTF archive data. We have found low overall variability indices (0.1–0.2) and a median spectral peak at 4.6 GHz, which is stable during the long-term period of monitoring. An analysis of the radio light curves reveals significant time delays (0.6 to 6.4 yrs) between the radio frequencies along with variability timescales ranging from 0.2 to 1.8 yrs in the source’s rest frame, which is similar to the blazars at lower redshifts. Spectral modeling suggests the presence of both synchrotron self-absorption (SSA) and free-free absorption (FFA) processes. Based on the SSA model, we provide estimates of the magnetic field strength which peaks at approximately 100 mG. A spectroscopic study with the BTA SCORPIO-1 spectrograph has found evidence of the regular motion of a neutral hydrogen envelope around the blazar center, which confirms the presence of a sufficient amount of gaseous matter to form an external FFA screen. The results highlight the importance of multi-wavelength and long-term monitoring to understand the physical mechanisms driving the variability in high-redshift blazars.

We present the results of a three-year X-ray, optical, and radio polarimetric monitoring campaign of the prototypical black hole X-ray binary Cyg X-1, conducted from 2022 to 2024. The X-ray polarization of Cyg X-1 was measured 13 times with the Imaging X-ray Polarimetry Explorer (IXPE), covering both hard and soft spectral states. The X-ray polarization degree (PD) in the hard state was found to be approximate to 4.0%, roughly twice as high as in the soft state, where it was around 2.2%. In both states, a statistically significant increase in PD with the energy was found. Moreover, a linear relation between PD and spectral hardness suggests a gradual and continuous evolution of the polarization properties, rather than an abrupt change of polarization production mechanism between states. The polarization angle (PA) was independent of the spectral state and showed no trend with the photon energy. The X-ray PA is well aligned with the orientation of the radio jet, as well as the optical and radio PAs. We find significant orbital changes of PA in the hard state, which we attribute to scattering of X-ray emission at the intrabinary structure. No significant superorbital variability in PD or PA was found at the period P-so = 294 d. We detect, for the first time in this source, polarization of the radio emission, with the PA aligned with the jet, and a strong increase of the PD at a transition to the soft state. We also find no correlation between the X-ray and optical polarization; if any, there is a long-term anti-correlation between the X-ray PD and the radio PD.

We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May-June. Companion multiwavelength data during the campaign are likewise shown. The 2-8 keV X-rays exhibit a net polarization degree PD=1.99%+/-0.13% (68% confidence). The polarization signal is found to increase with energy across IXPE's 2-8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA=-25.7+/-1.8 deg. East of North (68% confidence). This is consistent with being aligned to Cyg X-1's AU-scale compact radio jet and its pc-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree, but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trendline in the polarization degree between soft and hard states. Our favored polarimetric model indicates Cyg X-1's spin is likely high (a* above ~0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.

We report on an observational campaign on the bright black hole (BH) X-ray binary Swift J1727.8–1613 centered around five observations by the Imaging X-ray Polarimetry Explorer. These observations track for the first time the evolution of the X-ray polarization of a BH X-ray binary across a hard to soft state transition. The 2–8 keV polarization degree decreased from ∼4% to ∼3% across the five observations, but the polarization angle remained oriented in the north–south direction throughout. Based on observations with the Australia Telescope Compact Array, we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher-spatial-resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long (≳10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8–1613 is a member of a hitherto undersampled subpopulation.

We present a study of the flaring radio variability of four microquasars during last ten years with RATAN-600. The main aim of researches is a study of the daily light curves at seven frequencies of 1.2-30 GHz and in multi-azimuthal (MA) mode, when for 5h the fluxes are measured every 5-10 minutes at 4.7 and 8.2 GHz. In SS 433 dozens of bright flares were detected over last ten years. The brightest flare (5.5 Jy at 2.3 GHz) in the total history of GRS 1915+105 research occured in August 2023. In 2024 we have detected five giant radio flares in Cyg X-3 during hypersoft-to-hard X-ray states transits. These flares reached fluxes of 13-18 Jy and have similar properties: optically thick phase in the spectra in the beginning of a flare and the exponential fading for 5-30 days. We relate these events with an efficient formation of relativistic jets during the accretion of matter from a normal star. In the Gamma-ray binary LSI+61d303 with regular flares every 26.5 days, we have detected second period of 26.93 days that can be precession period of jets. We find a clear similarity of bright flares in microquasars.

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 period from 1997 to 2023. The radio data are represented by the measurements from the SAO RAS, IAA RAS, and CrAO RAS telescopes. The optical measurements were collected with the SAO RAS 1-m and 0.5-m reflectors. The archive data at 230 GHz from the Submillimeter Array and the $\gamma$-ray data from the Fermi-LAT mission were used too. A significant correlation between different spectral bands is found with time delays up to 1.7 years. The relation between time delay and frequency is well described by a linear law. The revealed features of MW variability for the quiet period and for flaring states suggest that the mechanisms dominating the radio-$\gamma$-ray variations are not substantially different. AO 0235+164 shows a total variability period of $\sim$6 years for all wavelength bands, and 1.4-2.3 years during the low state, which may reflect its general properties.

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 SAO RAS RATAN-600 radio telescope, the 5 and 8 GHz data from the IAA RAS RT-32 telescopes, and the 37 GHz data from the RT-22 telescope of CrAO RAS. The optical measurements in the R-band were collected with the SAO RAS 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes. Additionally, we used the archive data at 230 GHz from the Submillimetre Array 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 using the fractional variability indices, discrete correlation functions, Lomb-Scargle periodograms, and structure functions. A significant correlation (>= 2 sigma) between the radio, optical, and gamma-ray bands is found for all these periods with time delays from 0 to 1.7 yr. The relation between time delay and frequency is described by a linear law with a negative slope of -10 d GHz(-1). 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 yr are tentative, as the time span of the observations includes fewer than four full cycles for the radio and optical data and only about three cycles for the Fermi-LAT data. These results should be interpreted with caution, given the limited number of observed cycles and the influence of red noise. We used cluster analysis to reliably separate the high and low-activity states and determined statistical differences in the main properties of AO 0235+164 non-thermal emission. 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.

The results of the analysis of 205 brightest sources ( S>15 mJy), which were found in the sky survey at the declination of the pulsar in the Crab Nebula, are presented. The survey was conducted at a frequency of 4.7 GHz using a three-beam radiometer complex installed in the focus of the Western Sector of the RATAN-600 radio telescope in 2018–2019. Based on the measurements taken and the data collected in the CATS astrophysical catalogs database, the radio spectra of the objects were constructed. For a quarter of all detected sources, data at frequencies above 4 GHz were obtained for the first time, and for the rest they were supplemented. The variability of radiation sources on the scales of the year, from days to months, has been studied. The greatest change in the radio flux was found in the blazar B2 1324 + 22. The search for daily variability was carried out for 26 of the brightest sources with an average value of S_4.7∼ 250 mJy. All sources are identified with objects from optical and infrared catalogs. The radio luminosity was calculated for 112 objects with known redshifts.

The accretion of matter by compact objects can be inhibited by radiation pressure if the luminosity exceeds a critical value known as the Eddington limit. The discovery of ultraluminous X-ray sources has shown that accretion can proceed even when the apparent luminosity considerably exceeds this limit. A high apparent luminosity might be produced due to the geometric beaming of radiation by an outflow. The outflow half-opening angle, which determines the amplification due to beaming, has never been robustly constrained. Using the Imaging X-ray Polarimetry Explorer, we measured the X-ray polarization in the Galactic X-ray binary Cygnus X-3 (Cyg X-3). We found high, >20%, nearly energy-independent linear polarization orthogonal to the direction of the radio ejections. These properties unambiguously indicate the presence of a collimating outflow from the X-ray binary Cyg X-3 and constrain its half-opening angle to less than or similar to 15 degrees. Thus, the source can be used as a laboratory for studying the supercritical accretion regime. This finding underscores the importance of X-ray polarimetry in advancing our understanding of accreting sources.

The paper presents results of calculating the RATAN-600 beam pattern (BP) and BP drift scans of point radio sources in the West Sector radio telescope operation mode at a frequency of 4.7 GHz. When calculating the BP, the properties of the radio telescope antenna system in this operation mode were taken into account: the use of a large secondary mirror, asymmetric radiation of the primary mirror, and the location of the primary feeds (feed horns) along the focal line of the secondary mirror. The shape of the calculated drift scans of sources through the BP is compared with that of the experimental drift scans of sources obtained from observations in the West Sector. The main characteristics of the drift scans are calculated and compared when the radio telescope operates with the West and North Sectors. A new method for determination of flux densities of sources passing through the BP outside its central cross-section is proposed, and its accuracy is estimated.

We have been carrying out daily observations of bright microquasars at 1.2–20 GHz with the Northern sector of the RATAN-600 radio telescope for more than ten years. During the 2019–2021 observations we detected bright flares, which we call giant flares because fluxes reach record levels—above 20 Jy—during these events. In this paper we report the results of intraday variations of the microquasar Cygnus X-3 in multi-azimuth observations made with the ‘‘Southern sector with a flat-sheet reflector’’ during giant flares of Cygnus X-3. These were the first such observations made simultaneously at several frequencies on a short time scale (10 minutes). Observational data consists of 31 measurement made within $$\pm$$ 2.7 hours of the culmination of the object. We are the first to discover the evolution of the spectrum of the flare emission of Cygnus X-3 on a time scale comparable to the orbital period of the binary. The measurement data allowed us to determine the temporal and spectral parameters of radio emission, which are typical for synchrotron flare emission in relativistic jets. Evolution of the radio emission of X-ray binaries on short time scales is a key to understanding the formation of jet outbursts in the process of mass accretion of the matter of the donor star onto the relativistic object.

We report the first detection of the X-ray polarization of the bright transient Swift J1727.8−1613 with the Imaging X-ray Polarimetry Explorer. The observation was performed at the beginning of the 2023 discovery outburst, when the source resided in the bright hard state. We find a time- and energy-averaged polarization degree of 4.1% ± 0.2% and a polarization angle of 2.°2 ± 1.°3 (errors at 68% confidence level; this translates to ∼20 σ significance of the polarization detection). This finding suggests that the hot corona emitting the bulk of the detected X-rays is elongated, rather than spherical. The X-ray polarization angle is consistent with that found in submillimeter wavelengths. Since the submillimeter polarization was found to be aligned with the jet direction in other X-ray binaries, this indicates that the corona is elongated orthogonal to the jet.

With RATAN-600 radio telescope we can conduct studies of pulsed radiation of events associated with fast radio bursts(FRB), giant pulses (GP) of pulsars and flare activity of magnetars at high frequencies. Now the telescope has been equippedwith full-power radiometers with the highest possible time resolution and band division at a frequency of 4.7 GHz into fournarrow channels (150 MHz), which needed for detection of pulse shifts due to cosmic dispersion. As the main aim, thesearch for FRB in the blind 24h-surveys of sky regions has been conducted for more than four years on four radiometers(beams). In the sky regions at declinations of 33, 22, 5 and 11 degrees, no FRB with a flux greater than 5 Jy were detected.However, in the Crab Nebula, we registered seven GP from its 33-millisecond pulsar. The maximum pulse was above 100 Jy.Measurements of radio pulses from the X-ray magnetar XTE J1810−197 were carried out from 19 December 2018, when,after ten years on December 8, 2018 a bright X-ray flare occurred and weak radio pulses were detected with a pulsar rotationperiod of 5.54 seconds. Based on the arrival times of pulses in narrow channels, we confirmed the measure of dispersionDM=178 pc/cm 3 . The pulses themselves, with a total duration of about 200 ms, included up to 15 sub-pulses with a widthof 10 to 50 ms with a flux density of up to 5 Jy. During three months XTEJ1809−197 remained the brightest radio pulsarin the Milky Way.

The observed characteristics of the spectral and photometric variability of SS 433 are discussed based on the data for 2018–2021 and compared with earlier results. The change in the orbital period that we discovered earlier according to $$V$$ -photometry is confirmed by the data in the $$B$$ -filter, although with less accuracy. In the observation interval from 1978 to 2021, secular changes are not observed either in the stationary or moving H $$\alpha $$ lines. However, there are breaks in the precession phase up to $$ \pm 11$$ days, which appear at time scales less than 1 year and disappear in 2–3 years.

We present an analysis of the X-ray data obtained in the period of flaring activity of SS 433 in July and August 2018, during which the brightest radio flares over the entire history of its observations were detected at frequencies 2–5 GHz based on data from the RATAN-600 radio telescope. The Swift/XRT and NICER space observatory data were obtained immediately during the radio flares within the program of Target of Opportunity (ToO) observations. The Chandra/HETGS observations and the additional quasi-simultaneous NICER calibration observations were carried out in the active phase of the system between the radio intensity peaks. We show that during the peak radio fluxes the emission lines of the relativistic jets are detected with confidence in the X-ray spectrum, while their basic parameters remain stable, which can serve as evidence for the absence of significant violations in the jet collimation and acceleration mechanisms. At the same time, the X-ray intensity of the jets at these moments drops by a factor of 4–5 and is restored to its normal values within $${\sim}10$$ days. Anomalous deviations of the jet line positions from the predictions of the kinematic model were found in the period of activity and during the radio flares. Our modeling of the Chandra spectra using the emission model of baryonic jets in SS 433 point to rapid changes in the structure of the wind from the supercritical disk that partially blocks the emission from the hottest regions of the jets. The set of these factors points to a possible connection of the emergence of radio flares and active states of SS 433 with perturbations in the rate of mass transfer and outflow in the system.

The long-term monitoring at RATAN-600 of studies of bright X-ray binary stars in various ranges of the electromagneticspectrum, a search and detailed study of correlations between variable X-ray, radio and gamma radiation was carried out.It is a key point for understanding the formation of jet emissions from accreting matter onto a black hole (or neutron star).From April 2019 For a year, we began to use the multi-azimuth measurement mode on the Southern Sector antenna systemwith a flat reflector, when 31 measurements of flux densities at frequencies 4.7, 8.6, 15 and 30 GHz of several giant CygnusX-3 flares, SS433 [1] and GRS1915+105 bright flashes were carried out for 5–6 hours around the culmination of the source.In January 2020, Cyg X-3 switched to a hyper-soft X-ray state, the exit from which in early February led to the brightest theradio flash for the all history of its observations. The Cygnus X-3 flow density increased from 5 mJy to 20 Jy at a frequencyof 4.7 GHz and up to 22 Jy at 2.3 GHz in 2–3 days. In multi-azimuthal observations in the beginning phase, we registered alinear law of increase in the flux at times from 1 to 5 hours. Comparing the data of the space Gamma-ray telescopes (Swift,AGILE and Fermi) and the MAXI and NICER X-ray monitors on board the ISS, we found that flaring events from the radioto the Gamma-rays are interrelated, which is a reflection of the causal relationship of physical processes in the accretiondisk and in jet emissions. The spectral and time dependence of the evolution of flares allow us to model the synchrotronradiation of microquasars based on changes in the volume of jet emissions, the strength of their magnetic field and the modeof generation and absorption of radio radiation from relativistic electrons. Radio flares of the microquasar GRS1915+105,as a clear manifestation of a new jet activity, always have the character of a reaction to changes in the conditions forgenerating X-rays in the accretion disk (MAXI) and in the corona (Swift). We have studied in details periodic radio flaresfrom the X-ray binary with bright Gamma-ray radiation LSI+61d303 for more than 60 orbital periods. Undoubtedly, thenature of these flares changes dramatically depending on the known super-orbital 4.6-year period.

With the RATAN-600 radio telescope, we have detected about 1300 radio sources at 4.7 GHz frequency, identified withsources from other catalogs, mostly from the NVSS catalog at 1.4 GHz. From 6 June 2020 to 28 May 2021, the strip (width∼ 35 ′ ) of the sky on the microquasar GRS 1915+105 declination (Dec = +11 ◦ 56 ′ 44 ′′ ) was observed with a four-beamcomplex of four-channel sensitive radiometers, established in the focal line of the ’Western sector’ antenna of the RATAN-600. We summarized the data received in narrow channels to obtain maximum sensitivity of the flux (∼ 3 mJy/beam) inthe 600 MHz frequency band at the center 4.7 GHz frequency. This value is constrained only by the effect of confusion foran antenna beam with dimensions about 1 ′ × 35 ′ . We obtained about 20–25 high-quality day records divided by hours everymonth and 12 average hour drift scans for a year. We plotted and analyzed the light curves for bright variable sources forall 365 days. We identified the detected sources with the objects from the CATS database to plot compiled radio spectra ofthe sources. Most sources were identified as galaxies and quasars. Some supernova remnants were detected in cross-sectionsof the Galactic plane.

The microquasar Cygnus X-3 underwent a giant radio flare in 2017 April, reaching a maximum flux of similar to 16.5 Jy at 8.5 GHz. We present results from a long monitoring campaign carried out with Medicina at 8.5, 18.6, and 24.1 GHz, parallel to the Metsahovi radio telescope at 37 GHz, from 2017 April 4 to 11. We observe a spectral steepening from alpha = 0.2 to 0.5 (with S-nu proportional to nu(-alpha)) within 6 hr of the epoch of the flare's peak maximum, and rapid changes in the spectral slope in the following days during brief enhanced emission episodes while the general trend of the radio flux density indicated the decay of the giant flare. We further study the radio orbital modulation of Cyg X-3 emission associated with the 2017 giant flare and with six mini-flares observed in 1983, 1985, 1994, 1995, 2002, and 2016. The enhanced emission episodes observed during the decline of the giant flare at 8.5 GHz coincide with the orbital phase phi similar to 0.5 (orbital inferior conjunction). On the other hand, the light curves of the mini-flares observed at 15-22 GHz peak at phi similar to 0, except for the 2016 light curve, which is shifted 0.5 w.r.t. the other ones. We attribute the apparent phase shift to the variable location of the emitting region along the bent jet. This might be explained by the different accretion states of the flaring episodes (the 2016 mini-flare occurred in the hypersoft X-ray state).

ABSTRACT We present Low-Frequency Array (LOFAR) 143.5-MHz radio observations of flaring activity during 2019 May from the X-ray binary Cygnus X-3. Similar to radio observations of previous outbursts from Cygnus X-3, we find that this source was significantly variable at low frequencies, reaching a maximum flux density of about 5.8 Jy. We compare our LOFAR light curve with contemporaneous observations taken at 1.25 and 2.3 GHz with the RATAN-600 telescope, and at 15 GHz with the Arcminute Microkelvin Imager (AMI) Large Array. The initial 143.5-MHz flux density level, ∼2 Jy, is suggested to be the delayed and possibly blended emission from at least some of the flaring activity that had been detected at higher frequencies before our LOFAR observations had begun. There is also evidence of a delay of more than 4 d between a bright flare that initially peaked on May 6 at 2.3 and 15 GHz, and the corresponding peak (≳ 5.8 Jy) at 143.5 MHz. From the multifrequency light curves, we estimate the minimum energy and magnetic field required to produce this flare to be roughly 1044 erg and 40 mG, respectively, corresponding to a minimum mean power of ∼1038 erg s−1. Additionally, we show that the broadband radio spectrum evolved over the course of our observing campaign; in particular, the two-point spectral index between 143.5 MHz and 1.25 GHz transitioned from being optically thick to optically thin as the flare simultaneously brightened at 143.5 MHz and faded at GHz frequencies.