Most important results of SAO RAS for 2024
Here you would find a brief summary of the most important results of scientific research carried out by our researchers during the last year, presented by the observatory to the Department of Physical Sciences of the RAS. Access here the archives of our results from 1993.
Metagalaxy
Six- and Two-Year Quasi-Periods of Long-Term Variability of the Blazar AO 0236+164 Determined for the First Time from Multiwavelength Observations
The multiwavelength properties of the emission variability of the blazar AO 0235+164 are presented on a 27-year time scale from 1997 to 2023. The measurements were made with the RATAN-600 telescopes (SAO RAS) in the range of 1-22 GHz, RT-32 (IAA RAS) at 5 and 8 GHz, and RT-22 (CrAO RAS) at 37 GHz. In the submillimeter range, the SMA data at 230 GHz were used, in the γ-range (0.1-100 GeV) — Fermi-LAT. Measurements in the optical range (the R band) were obtained with the SAO RAS Zeiss-1000 and AS-500/2 telescopes. For the analysis, the light curves are divided into 4 epochs, each associated with one major flare, with a low-state epoch in 2009-2014 highlighted separately. Correlations between the radio, optical, and γ-ranges are found in all 4 activity epochs with delay times of up to 1.7 years (significance ≥2σ). A linear relationship was found between frequency and delay time with a slope of about −10 days/GHz, which means that the flare starts and develops at high frequencies followed by spreading to lower frequencies. During the period of low activity in 2009-2014, the variability in the optical and γ-ranges reaches 30 and 50%, which may be caused by the interaction of shock wave remnants that followed large bursts. The correlation between the radio, optical, and γ-ray light curves found for this period for the first time may indicate that the mechanisms causing the low-state emission variability are no different from those of the active phase.
The Lomb-Scargle periodograms calculated taking into account the influence of red noise revealed the presence of quasi-periods of about 6 years (up to 4σ) at all wavelengths in the period of 1997-2023. For the quiescent-state epoch, a period of about 2 years (≥2-3σ) was detected for the first time. The quasi-period of 6 years may reflect the time between the most noticeable flares in the light curves, which may have a stochastic nature, and the detected quasi-periodicity has no close relationship with the characteristics of the active nucleus and the relativistic jet. However, we suggest that the periodicity detected for the low state reflects the basic properties of the AGN in AO 0235+164.
Authors:
Vlasyuk V.,1 Sotnikova Yu.,1,2 Volvach A.,3 Mufakharov T.,1,2 Kovalev Yu.A.,4,5 Spiridonova O.,1 Khabibullina M.,1 Kovalev Yu.Yu.,6 Mikhailov A.,1 Stolyarov V.,1 Kudryavtsev D.,1 Mingaliev M.,1,2,7 Razzak S.,8 Semenova T.,1 Kudryashova A.,1 Bursov N.,1 Trushkin S.,1 Popkov A.,4,9 Erkenov A.,1 Rakhimov I.,7 Kharinov M.,7 Gurwell M.,10 Tsybulev P.,1 Moskvitin A.,1 Fatkhullin T.,1 Emelyanov E.,1 Arshinova A.,1 Yuzhanina K.,1 Andreeva T.,7 Volvach L.,3 Ghosh A.8
1SAO RAS, 2KFU, 3CrAO RAS, 4ASC LPI, 5INR RAS, 6MPIfR, 7IAA RAS, 8University of Johannesburg, 9MIPT, 10Harvard-Smithsonian Center for Astrophysics
Published:
Vlasyuk V. V. et al., Multiwavelength variability of the blazar AO 0235+16, MNRAS, 2024, Volume 535, Issue 3, Pages 2775-2799
Detection and Study of Five Giant Flares of the Microquasar Cyg X-3 in 2024
In February-August 2024, during regular multi-frequency (1-30 GHz) monitoring with the SAO RAS RATAN-600 radio telescope, five giant (above 10 Jy) flares from the unique X-ray binary Cygnus X-3, which includes a black hole (BH) and a Wolf-Rayet star, were detected. In such rare flares, Cygnus X-3 became the brightest radio source in the Milky Way, not counting several remnants of historical supernovae. It was found that the onset of each of the five flares was unambiguously associated with the detection of significant high-energy gamma radiation in the range of 0.1-300 GeV by the Fermi space observatory. All flares occurred during the transition of the system from the hyper-soft X-ray state to the hard state, when hard X-ray emission (Swift/BAT, 15-50 keV) arose and the soft radiation flux (MAXI, 4-10 keV) dropped sharply. We explain this behavior within the framework of a physical picture with a changing and, as was recently revealed in X-ray polarization measurements at the IXPE observatory, supercritical rate of the matter accretion onto the BH, the state of the hot corona and accretion disk, and the processes of formation and collimation of jet emissions. The radio outbursts evolved on different scales from 10 to 60 days and had similar properties: in the first hours, the radio flux grew linearly with time, more slowly at low frequencies; after two to three days, there was an exponential attenuation with a gradual softening of the radio spectrum (the spectral index changed from −0.1 to −0.9). Such specific properties clearly indicated the generation of synchrotron radio emission by relativistic electrons in jet ejections. In turn, these electrons, scattering the optical radiation of the star in the process of inverse Compton scattering, led to the generation of high-energy gamma rays. On average, the flare radio emission released a huge amount of energy, about 1039 J. The spectra of the onset of the June flare with a characteristic dip at frequencies below 3 GHz, probably caused by thermal electrons in the jets, were obtained. For the first time in the world, it was possible to study in detail the spectral and temporal variability of Cyg X-3 at times from 9 to 300 minutes in a new fast-shift mode at the “Southern sector with a flat reflector” antenna system of RATAN-600 at two frequencies of 4.7 and 8.2 GHz.
Authors:
Trushkin S.A., Shevchenko A.V., Bursov N.N., Nizhelskij N.A., Tsybulev P.G. (SAO RAS)
Published:
1. Veledina et al., Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE, Nature Astronomy, Volume 8, p. 1031-1046
2. Trushkin S., Shevchenko A., Bursov N., Nizhelskij N., Tsybulev P., The flaring activity of microquasars is the key to understanding the processes of accretion and generation of jet emission, Modern astronomy: from the Early Universe to exoplanets and black holes, Proceedings of the VAK-2024 conference, Aug 25–31, 2024 — Moscow, RIOR, 2024, ISBN 978-5-369-02160-6
Details
Archive of achievements, Metagalaxy sector
Galaxy
Nature of the Emission Spectrum of NGC 7793 P13: Evidence for Accretion from the Wind of a Donor Star
Based on the results of calculations of non-LTE models of extended atmospheres for the ultraluminous X-ray pulsar NGC 7793 P13 (a system consisting of a neutron star and, presumably, a B9 Ia supergiant), it is shown that most of the observed features of the optical spectrum of the source are naturally reproduced within the framework of a spherically symmetric model of the donor star atmosphere with a mass loss rate in the wind Ṁ ≈ 6 × 10−6 M⊙ yr−1. This value is in good agreement with the estimate of the mass loss rate in the wind of the P13 donor calculated by El Mellah et al. (2019) based on the observed X-ray luminosity of the system for the case of accretion from the wind. Thus, the first reliable evidence for the implementation of such an accretion mechanism in ultraluminous X-ray sources with a neutron star is obtained. The high mass loss rate relative to the standard values for the supergiant B9 Ia can be explained by the high rotation velocity of the star. The mechanism of radiation-field modification in the extended atmosphere model has been implemented and successfully applied for the first time in the problem of modeling the optical spectrum of an ultra-luminous X-ray source, which made it possible to take into account the irradiation of the relatively cold donor wind matter by X-ray radiation from the accretion disk and, as a result, to obtain the observed emission intensity of He II 4686 and improve the agreement between the model and observed neutral helium line profiles. The problem of preserving the wind of a donor star under conditions of irradiation by a powerful X-ray source is considered: it is shown that it can be solved at a qualitative level if, instead of an isotropic source, a source with moderate collimation of X-ray radiation is considered.
Authors:
Vinokurov A. S.*, Kostenkov A. E., Solovyeva Yu. N., together with Atapin K. E. (SAI MSU)
Published:
Vinokurov A. S., Kostenkov A. E., Atapin K. E., Solovyeva Yu. N. “Nature of the Emission Spectrum of NGC 7793 P13: Modeling the Atmosphere of the Donor Star”, Astrophysical Bulletin, Volume 79, Issue 3, pp. 399-413, DOI: 10.1134/S1990341324600558
Archive of achievements, Galaxy sector
Solar system
Detection of Depression Effects in Radio Emission from the Solar Corona
Absorption in many fine structures in coronal plasma has been detected using radio observations. The data were obtained at RATAN-600 with a new spectral complex with a relative frequency resolution of 10−5 and a time resolution of 8 ms in the range of 1–3 GHz in the radio emission spectra of individual active regions (ARs), prominences, and filaments. Similar structures in the form of “coronal rain” are studied in optics in the X-ray and EUV lines at large telescopes with diameters of 1.6 m and 4.0 m; but for the first time, they were discovered in the spectra of the corona at radio waves. The spectra of the quiet Sun and active regions of NOAA 13507(8) were obtained. New spectral capabilities of the instrument for studying the fine structure of the corona can be used to solve the problem of heating the solar corona and to measure its temperature balance.
Authors:
Bogod V.M., Lebedev M.K., Ovchinnikova N.E., Ripak A.M., Storozhenko A.A., Kurochkin E.A. (SAO RAS)
Published:
1. Bogod V.M., Lebedev M.K., Ovchinnikova N.E. et al. On a new concept of spectral radiometry at RATAN-600 // Izvestiya Krymskoy Astrophysical Obs. 2023. Vol. 119. No. 4. P. 17–26.
2. Ovchinnikova N., Bogod V., Lebedev M., Observation at radio frequencies of the hydroxyl (OH) absorption line in filaments and prominences above active regions of the Sun, Solar-Terrestrial Physics, vol. 10, issue 3, pp. 18-24, DOI:10.12737/stp-103202403
Archive of achievements, Solar system sector
Hardware and methodological developments
Development of a Photodetector System Optimized for Photometry Methods Based on a Large-Format CMOS Photodetector
A large-format high-speed photodetector system (PDS) based on a back-illuminated CMOS photodetector GSENSE6060BSI (GPixel, China) with a 6K×6K-element format and a diagonal of 86.8 mm has been developed and manufactured to use at telescopes of SAO RAS and other observatories. The detector is located in a vacuum gaseous head at atmospheric pressure. Due to the antireflective coating of the photodetector, the PDS provides high quantum efficiency of detection of more than 95% at the peak sensitivity at a wavelength of 580 nm. The system ensures high accuracy in maintaining the temperature of the photodetector at a level of ±0.1°C, which allows stabilizing the gain of the video channel (gain instability is 0.064%). The camera cooling system is built on thermoelectric modules and includes air cooling with the possibility of using a liquid heat exchanger. The PDS controller implements the mode of simultaneous image reading in two 12-bit video channels with different gain and their subsequent combination into one frame with an extended 16-bit dynamic range (HDR, High Dynamic Range). The improved combination of frames with high and low gain into an HDR frame ensures the linearity of the “light-signal” transfer characteristic without gain shifts and dispersion at the junction of video channels. The implemented HDR frame mode (necessary for photometry of weak objects) ensures a high dynamic range and nonlinearity of the video channel of 0.69% and has no analogues among photoreceiving systems (of other manufacturers) available for purchase in the Russian Federation. The read images contain geometric noise caused by interference from the operation of the multiplexer control signals and the heterogeneity of numerous readout channels. Real-time frame correction methods allow minimizing geometric noise to values comparable to CCD photodetectors. For the use of PDS in long-exposure photometry methods, modes of dark current reduction, built-in zero subtraction, and video channel gain stabilization are provided. It is also possible to use PDS in fast spectroscopy methods, as part of adaptive optics systems, and fast sky surveys.
Authors:
Afanasieva I.V., Murzin V.A., Ardilanov V.I., Ivaschenko N.G., Pritychenko M.A. (SAO RAS)
Published:
1. Vlasyuk V.V., Afanasieva I.V., Ardilanov V.I., Murzin V.A., Ivaschenko N.G., Pritychenko M.A., Dodonov S.N., Large-format imaging systems based on solid-state detectors in optical astronomy, Uspekhi Fizicheskikh Nauk, 194, 432–445 (2024), doi: 10.3367/UFNr.2023.04.039575
2. Afanasieva I., Murzin V., Ardilanov V., Ivaschenko N., Pritychenko M., Large-format photodetecting system pCam6060 with a GSENSE6060BSI CMOS detector, developed at SAO RAS and optimized for photometric methods, Modern astronomy: from the Early Universe to exoplanets and black holes, Proceedings of the VAK-2024 conference, Aug 25–31, 2024 — Moscow, RIOR, 2024, ISBN 978-5-369-02160-6
Archive of achievements, Instrumental and Methodological Development sector
Astronomical education
Archive of achievements, Astronomical education sector