Nikolai S. Kardashev

The unique BL lac object S5 0716+714

A cluster of three galaxies has been observed around the unusual object S5 0716+714, which displays a lineless continuum throughout all wavelength intervals (from radio to gammarays) and rapid variability (even within a day). The galaxies have very similar redshifts: 0.264 ± 0.004, 0.257 ± 0.005, and 0.249 ± 0.003. for the first time, our observations with the 6-m telescope of the Special Astrophysical Observatory equipped with the multimode SCORPIO spectral camera have revealed some evidence for the host galaxy around the object—an elliptically shaped flux excessively extended by 3″–5″ from S5 0716+714.

A multi-frequency study of brightness variations of the blazar 0716+714

Based on long-term monitoring at five radio frequencies between 4.8 and 37 GHz performed at the Radio Astronomy Laboratory of the Crimean Astrophysical Observatory, the University of Michigan Radio Astronomy Observatory, and the Metsähovi Radio Observatory, we have analyzed two flare events in the blazar S5 0716+714 during the last five years. The time separation between the flares is in agreement with data derived earlier from a spectral analysis of flux variations at the above frequencies, which revealed a periodic component with a period of about four years in the variations. We consider the dynamics of strong flares in 2003 and 2007 and determine the delays between the development of the event at various radio frequencies. Our data can be used to draw conclusions about the kinematic and dynamical properties of the source.

Long-term monitoring of the blazars AO 0235+164 and S5 0716+714 in the optical and radio ranges

Long-term, multi-frequency optical and radio monitoring data for the Active Galactic Nuclei (AGNs) AO 0235+164 and S5 0716+714 are used to derive the characteristics of their radiation on time scales from hours to decades. Structure-function and harmonic analyses are carried out to determine the parameters of the radiation of these AGNs and explain their physical characteristics. Periodic components that could be associated with the motion of companions along an orbit in a close binary system of two supermassive black holes are identified. Both of the analysis methods used yield consistent results for the harmonic components. The results obtained are consistent with the idea that we are viewing systems of two supermassive black holes in a stage of their evolution that is close to coalescence. The substantial energy release of these AGNs can be interpreted as dynamical losses arising during the motion of the companion about the common center of gravity in a dense accreting medium, sometimes crossing through the accretion disk.

The rapid variability of blazars at optical wavelengths

We monitored five active galactic nuclei in the R optical band with a CCD mounted on the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory from April 2001 to August 2003. Three sources displayed intraday variability on several nights. Stronger variability was detected on time scales from two days to a week. The two-year light curves are presented for four of the observed objects.

Observational effects in black and white holes (dynamical wormholes)

The models of wormholes with a topology based on a Reissner-Nordström black and white hole are considered. In these models, there are one entrance in one universe (a black hole) and one exit into another universe (a white hole) corresponding to this entrance. The passage of matter through the wormhole in these models is possible only in one direction (from past to future). All models are considered under the assumption of spherical symmetry. It is shown that all models without a throat do not violate the null energy condition. The model of a Reissner-Nordström black hole containing no singularities inside the horizon has been constructed. The trajectories of particles and light rays passing from one universe into another have been constructed for the simplest Reissner-Nordström black and white hole. Distinctive features have been found for the images of objects from another universe observed through such objects. The characteristics of these images are compared with those for ordinary wormholes.

Investigating statistical and spectral characteristics of the radio sources from the RadioAstron catalog at millimetric wavelengths

We consider some statistical characteristics of radio sources at 22 GHz in the framework of the preparatory works on the RadioAstron space mission. The expected density of radio sources with inverted spectra is estimated. Based on the observations of the radio sources from the preliminary RadioAstron sample, we compare the expected and measured angular densities of the radio sources with inverted spectra. The optical characteristics of the objects with inverted spectra and of the sources from the complete sample are compared as well. We present some spectral parameters of the radio sources observed at two different frequencies. Some conclusions about the completeness and reliability of the preliminary RadioAstron catalog are made.

Current status of the space mission Millimetron

Millimetron is a planned space observatory working in millimeter, submillimeter and far infrared bands with 10-m actively cooled mirror. It will operate in two modes. In the single dish mode with very high sensitivity Millimetron will address the key problems of cosmology, star and planet formation, interstellar medium and galaxy evolution left open by previous missions. The second mode is the Space-Earth radio interferometer with extremely high angular resolution and it is aimed at observations of the sub horizon scale structures of black holes.

Non-stationary emission of the blazar S4 0954+658 over a wide range of wavelength

Data from long-term multi-frequency monitoring are used to analyze variations in the flux density of the active galactic nucleus S4 0954+658. These data were obtained at the CrimeanAstrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, the University of Michigan Radio Astronomy Observatory, the Cavendish Laboratory of Cambridge University, the Special Astrophysical Observatory, and the National Institute of Astrophysics, Optics, and Electronics; 0.1–300-GeV data from the Fermi space gamma-ray observatory were also used. Radio data at 4.8, 8, 14.5, 15, 22.2, and 36.8 GHz are considered together with optical and near-infrared data in the R, J, H, and K filters.In the framework of a model in which binary supermassive black holes (SMBHs) are present in active galactic nuclei, harmonic and structural analyses are carried out to establish the orbital (Torb ≈ 780 yrs) and precessional (Tpr ≈ 7800 yrs) periods in the rest frame of the source.The development of the most powerful flare ever observed in this object, which occurred in February 2015, is considered. The delay in the flare’s development in different wavelength ranges from the gamma-ray to the radio is determined. both the magnitude of the delays and the durations of the flares themselves suggest that the physical characteristics of S4 0954+658 are similar to those of the blazar S5 0716+714, which displays evidence of a high γ factor for the jet motion and high superluminal speeds in the jet. The masses of the components of the binary SMBH (M and m), the dimensions of their orbit, and the velocity of the lower-mass SMBH about the central SMBH are estimated. The derived physical characteristics are subject to a comparative analysis.

A Brief History of Radio Astronomy in the USSR

1 Radio Astronomy Studies at the Lebedev Physical Institute.- 2 Radio Astronomy Studies in Gorkii.- 3 Radio Astronomy at GAISH and IKI.- 4 GAO Department of Radio Astronomy.- 5 Radio Astronomy at the SAO.- 6 Byurakan Astrophysical Observatory and other Armenian Organisations.- 7 Crimean Astrophysical Observatory.- 8 Academy of Sciences of the Ukrainian SSR.- 9 IRE of the USSR Academy of Sciences.- 10 IZMIRAN.- 11 SibIZMIRAN.- 12 The RO of the Latvian Academy of Sciences.- 13 Leningrad State University.