Search

As a result of detailed observations of the water vapour maser at the 22-m Simeiz radio telescope from 2017 June to 2019 December, two powerful flares were recorded in the Galactic source W49N, which occurred near the high-velocity feature −40 km s−1. The extremely powerful flare had an ultrashort duration of about 2 d and reached a flux density of 110 kJy. An ultrashort flare occurred at the top of a less powerful, but ten times longer one. To our knowledge, a flare of a water maser with such extreme characteristics has never been reported before. A correlation between the exponential increase and decrease in the flare flux density and decrease in line widths with increasing flux density, which is characteristic of an unsaturated maser, is found. The maser of the third flare was in a saturated state and provided a large input flux density 9.5 kJy for the occurrence of two powerful flares, the masers of which were in an unsaturated state. New data have been obtained concerning the physical characteristics of the water maser phenomenon during powerful flares.

High-mass protostars (M$_{\star} >$ 8 M$_{\odot}$) are thought to gain the majority of their mass via short, intense bursts of growth. This episodic accretion is thought to be facilitated by gravitationally unstable and subsequently inhomogeneous accretion disks. Limitations of observational capabilities, paired with a lack of observed accretion burst events has withheld affirmative confirmation of the association between disk accretion, instability and the accretion burst phenomenon in high-mass protostars. Following its 2019 accretion burst, a heat-wave driven by a burst of radiation propagated outward from the high-mass protostar G358.93-0.03-MM1. Six VLBI (very long baseline interferometry) observations of the raditively pumped 6.7 GHz methanol maser were conducted during this period, tracing ever increasing disk radii as the heat-wave propagated outward. Concatenating the VLBI maps provided a sparsely sampled, milliarcsecond view of the spatio-kinematics of the accretion disk covering a physical range of $\sim$ 50 - 900 AU. We term this observational approach `heat-wave mapping'. We report the discovery of a Keplerian accretion disk with a spatially resolved four-arm spiral pattern around G358.93-0.03-MM1. This result positively implicates disk accretion and spiral arm instabilities into the episodic accretion high-mass star formation paradigm., Published in Nature Astronomy in 2023

In 2019 September, a sudden flare of the 6.7 GHz methanol maser was observed toward the high-mass young stellar object (HMYSO) G24.33+0.14. This may represent the fourth detection of a transient mass accretion event in an HMYSO after S255IR NIRS3, NGC 6334I-MM1, and G358.93−0.03-MM1. G24.33+0.14 is unique among these sources as it clearly shows a repeating flare with an 8 yr interval. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we observed the millimeter continuum and molecular lines toward G24.33+0.14 in the pre-flare phase in 2016 August (ALMA Cycle 3) and the mid-flare phase in 2019 September (ALMA Cycle 6). We identified three continuum sources in G24.33+0.14, and the brightest source, C1, which is closely associated with the 6.7 GHz maser emission, shows only a marginal increase in flux density with a flux ratio (Cycle 6$/$Cycle 3) of 1.16 ± 0.01, considering an additional absolute flux calibration uncertainty of $10\%$. We identified 26 transitions from 13 molecular species other than methanol, and they exhibit similar levels of flux differences with an average flux ratio of 1.12 ± 0.15. In contrast, eight methanol lines observed in Cycle 6 are brighter than those in Cycle 3 with an average flux ratio of 1.23 ± 0.13, and the higher excitation lines tend to show a larger flux increase. If this systematic increasing trend is real, it would suggest radiative heating close to the central HMYSO due to an accretion event which could expand the size of the emission region and/or change the excitation conditions. Given the low brightness temperatures and small flux changes, most of the methanol emission is likely to be predominantly thermal, except for the 229.759 GHz (8−1–70 E) line known as a class I methanol maser. The flux change in the millimeter continuum of G24.33+0.14 is smaller than in S255IR NIRS3 and NGC 6334I-MM1 but is comparable with that in G358.93−0.03-MM1, suggesting different amounts of accreted mass in these events.

Using long-term monitoring data of water-vapour masers, here we examine a composite powerful flare of extremely short duration (∼12 d), which occurred in IRAS 16293-2422. The most powerful part of the flare was located on top of a less strong but more prolonged flare, which in turn is also a composite. The configuration of three radiating maser condensations located on the line of sight to the observer was detected for the first time. This made it possible to confirm one of the hypotheses for the activation of water masers, based on an increase in the maser’s amplification length by the components located in the observer’s line of sight. The unsaturated state of the two most powerful maser flares have been confirmed and some significant water maser parameters were obtained.

Multicolor photometric observations in the optical band and a comprehensive study in the X-ray, gamma-ray, and radio bands are presented for GRB 181201A and its afterglow. The optical observations began $${\sim}0.5$$ day after the burst and lasted almost continuously for $${\sim}24$$ days. They were resumed after eight months, which allowed us to determine the contribution of the host galaxy to the measured fluxes and to estimate the related extinction. Such complete coverage of the light curve became possible owing to the coordinated work of a network of nine telescopes worldwide. Convincing evidence of an incipient supernova explosion at the location of the burst source was obtained at the end of the first series of observations. Thus, GRB 181201A became yet another event that confirmed the association of gamma-ray bursts with supernovae. Thirty such events based on photometric observations of burst afterglows were known before it. A comparison of the supernova-induced excess emission in the light curve of the afterglow from GRB 181201A with other events has allowed some of the supernova parameters to be determined.

Water maser monitoring observations of W49N were carried out with the 22-m Simeiz radio telescope from 2017 May to 2020 February. A series of flares near a high-velocity spectral feature at −60 km s−1 was detected, including a very short duration flare (less than a month) that was very powerful (at its maximum, it reached a flux density of 77 kJy). This flare occurred on top of a less powerful, but longer-lasting flare. A correlation is revealed between the exponential growth of the flux density and the decrease in the linewidth, which is characteristic of the behaviour of a maser in an unsaturated state. In connection with flare phenomena in the framework of the model of close binary massive star systems (CMSSs), we consider the possibility of detecting gravitational waves from CMSSs in the regions of active star formation.

The spectral structure and trends in variations of local nonmodeled deformations of Earth at the Simeiz site are the focus of this study. In the time series of radio interferometric observations carried out within international projects, periodic components in addition to surface deformations at the Simeiz site were found and modeled. The amplitude of the most significant seasonal component is 3.34 mm. With the frequency−time wavelet transform, the time localization and changes in the power and frequency of oscillations were revealed for the time interval from 1980 to 2014. It was found that regular solar and geodynamic oscillations observed in the satellite data influenced the insolation of Earth’s surface at the Kara-Dag site in the period from 1983.5 to 2005.5. Parameters of the seasonal component were determined. Possible causes of the increase in the amplitude of the seasonal component are discussed.

We report the earliest detection of the 19.967-GHz [transition 21–30E (t = 0)] methanol maser associated with the massive star-forming region G358.93–0.03. The flare was detectable from 2019 January 23 to March 5, for only 44 d. It turned out to be the most powerful 19.967-GHz maser in the Galaxy in the entire history of observations, taking into account the 104-Jy flux from it on the Earth’s surface and the distance to the source, 6.75 kpc. The 19.967-GHz maser flared contemporaneously with the first of two flares detected in associated 20.971-GHz methanol masers. We estimated that the ratio of flux densities between these two transitions is F20.971/F19.967 = 14 ± 4, increasing to >520 in the second flare. We discuss the differences between the two flares in the 20.971-GHz methanol masers and the consequence thereof.

Using a new model based on the consideration of close binary systems (CDS) of supermassive black holes (SMBHs), we obtained data for the OJ 287 blazar, which is necessary for finding the parameters of the OJ 287 gravitational radiation. We used the results of multi-frequency monitoring performed only in the radio band. The application of harmonic analyses of observational data allowed us to construct a model of CDS consisting of two SMBHs of comparable masses, which made it possible to find the power of gravitational radiation coming from OJ 287, variations in the orbit of the double SMDS, and to consider the possibility of experimentally determining changes in these parameters in the system. Variants of radiation of electromagnetic and gravitational waves coming from OJ 287 in various states of object activity are considered.

We have investigated the methanol CH3OH lines at frequencies of 19.967 GHz [21-30 E(vt = 0) transition] and 20.971 GHz [101-112 E+(vt = 1) transition] toward the massive region of active star formation G358.931-0.030 with the RT-22 (Simeiz) and RT-26 (HartRAO) radio telescopes. Two new flares have been detected. One of the flares (at 20.971 GHz) is extremely powerful in the frequency range 192-26 GHz. We present our monitoring of the flaring events detected at 19.967 and 20.971 GHz. The time dependence of the flare amplitude reflects the complex structure of the maser emission regions. The velocity structure of the flares is considered.

Analysis of the time series of climatic characteristics of the Crimean peninsula for the period of 19832-2005 showed an enhanced growth (compared to other points of the Crimea) of the insolation of the Earth’s surface at Kara-Dag and an anomalous temperature decrease of the Earth’s surface at the Cape Fonar. The parameters of the geomagnetic field of the Kara-Dag mount were estimated. To derive the geomagnetic field variations in Crimea, the IGRF-12 online calculator was used. Regular oscillations were found in the analyzed time series, whose periods coincide with the solar-terrestrial cycles. The coherence functions were calculated and the periods of coherent variations were determined. As a result of the analysis of corrections to the vertical deformations of the Earth’s surface, a seasonal component was selected at Katsiveli and its parameters were calculated.

Climatic characteristics of the Crimean peninsula were analyzed on the basis of climatic parameters measured every day onboard NASA satellites for the period of 1983−2005. An accelerated increase in the insolation of Earth’s surface at the Kara-Dag site (as compared to that at other sites in Crimea) and an abnormal decrease in the surface temperature at the Fonar site have been revealed. The results of frequency−time wavelet analysis of local data on the insolation and temperature of the terrestrial surface enabled us to isolate periodic oscillations, the periods of which coincide with astronomical cycles, and determine an era of anomalous deviations from general trends of 1990−1995. From the analysis of corrections for vertical deformations of Earth’s surface at the Katsiveli site, a seasonal component was detected and parameters of this oscillation were calculated. Coherent variations with periods of approximately 10−12 and 60−70 years, which were found here, are inherent in the processes of different physical nature. They can be attributed to the global cycles in the Solar System, the manifestation of which in climatic and geophysical local processes is a result of the general trend towards synchronization. In this process, coherent variations of multiple or commensurate frequencies, may appear.

—Powerful flares in Galactic kilomasers are closely associated with regions of intense star formation. They contribute to the elucidation of physical processes occurring in these structures. We have recorded a superpowerful flare in the high-velocity −81 km s−1 line in the Galactic maser source W49N. As a result of our monitoring at the RT-22 (Simeiz), RT-32 (Torun), RT-100 (Effelsberg), and RT-32 (Medicina) radio telescopes in the period from September 2017 to November 2018, we have obtained the shape of the spectral flux density variations in the source with time. At the peak the flux density reached P ≈ 5 × 10^4 Jy. The flare has a double pattern and different durations of its components. The pattern of spectral flux density variations for the first flare with a considerably shorter duration is apparently related to a sharp increase in the density of the medium and the photon flux and to a significant rise in the temperature to hundreds of kelvins. We propose a mechanism of primary energy release related to the existence of close massive multiple systems in star-forming regions. A powerful gravitational perturbation at the system’s periastron can lead to a partial ejection of the envelope of the central massive star in a direction close to the major axis of the ellipse of the companion’s orbit. This explains the significant asymmetry of high-velocity lines in W49N. The ejected envelope is an energy source more significant than the stellar wind and can explain the giant flares in the object. Further comprehensive studies in this direction, including monitoring VLBI studies, are needed to confirm this assumption.

Variations of the 3C454.3 radio source flux on different time scales (from decades to a year) are analyzed according to the data of long-term multi-frequency monitoring. The anomalously prolonged outbreak that occurred in the facility in 2013-2018 is twice as long as the possible orbital period of the rotation of the supermassive black hole (SMBH) companion located in the center of the parent galaxy. The smallscale fluctuations of the radiation flux density accompanying the flare can be a consequence of the inhomogeneities of matter with dimensions of the order of 1015 cm or more in the central SMBH's AD and adjacent areas.

Results of systematic observations of a sample of bright H2O maser sources with fluxes, on average, exceeding 200 Jy in their main spectral feature during April- September 2017 (G25.65+1.05, G25.825-0.178, G27.184-0.082, G34.403+0.233, G35.20-0.74, G43.8-0.13, G107.30+5.64) are presented. These observations were carried out in preparation for Very Long Baseline Interferometry observations with an array including the Crimean Astrophysical Observatory 22-m radio telescope. All these sources display fairly strong variability during the time interval considered, encompassing fluxes from ∼40 to ∼2300 Jy. A flare reaching ∼17 000 Jy was detected at a velocity of 42.8 km/s in G25.65+1.05 on September 7, 2017, which subsequently grew to 60 000 Jy at the end of September 2017. This suggests the presence of compactmaser structures.

To study the changes in the local variations of geomagnetic field, the Karadag point was chosen due to the fact that we found previously on increased insolation and the surface temperature of the earth at this point over the last century (compared to other Crimea points). For the analysis, the data calculated by the authors with a calculator of the 12th model of the International Geomagnetic Standard Field (The International Geomagnetic Reference Field — IGRF-12) were used. A polynomial model of the sixth order of secular variations of geomagnetic declination was constructed at the Karadag point for the period 1900—2017. The estimates of the accuracy of approximation by this model of the data calculated with the IGRF-12 calculator are as follows: R-square = 0.8892 (most of the variance is taken into account by the model); corrected R-square = 0.8833; mean square error of approximation RMSE = 0.01395. When comparing the graphs of secular variations of geomagnetic declination at the Karadag point calculated by means of the IGRF-12 calculator and using a polynomial order model, a leap in 1969 is detected. In addition, it was found that the most drastic changes in geomagnetic declination occurred at intervals of 1944—1945 and 1974—1975. Coherent variations are established. An analysis of the calculated coherence functions suggests the existence of a statistical connection between variations with a period of 36.4 years (the square of the coherence modulus is 62 %) in the secular variations of geomagnetic declination at Karadag and in changes from year to year of day duration; between variations with periods of 10.5 years (the square of the coherence modulus is 86 %) in the secular variations of geomagnetic declination at Karadag and changes in the number of sunspots from year to year. There is a similarity between the tendency of changes in the secular variations of geomagnetic declination at Karadag and the tendencies of changes in the northern component of the velocity of the geomagnetic pole in the Northern Hemisphere during recent years.

Data analysis of long-term multi-frequency monitoring of active galactic nucleus (AGN) AO 0235+164 in the millimeter wavelength range are presented. Using the harmonic analysis of observational data, the presence of orbital and precession periods in the binary system from supermassive black holes (SBHs) is determined: Torb ≈ 2 years and Tpr ≈ 8 years. The indicated periods are in agreement with similar periods found for other bright AGNs. In the AO 0235+164 system, other combinations of periodic components are also determined, which are possibly related to the nutation period. According to observational data of the development of flare phenomena at different frequencies, a cross-correlation analysis was performed and the shift delays of the flare times occurring at different wavelengths were determined. It was confirmed, by analogy with other AGNs, an empirical relation, to which the delays of flux variations with a frequency are obeyed having the form of the inverse logarithmic dependence. The nature of the delays can indicate the internal character of the variability of AGN emission fluxes obtained at frequencies of the centimeter and millimeter wavelength ranges. The hypothesis of jet activity of AGNs is confirmed, in which plasma formation, moving from the sources of ejection, becomes optically thin consistently on ever longer waves. Decreasing delays between frequencies for the flare in 2015 compared to the previous flare in 2008–2009 indicates a possible configuration variation in AO 0235+164 associated with decreasing in the angle between ejections and the direction to the observer.

The results of long-term monitoring of the Galactic maser source IRAS 18316-0602 (G25.65+1.05) in the water-vapor line at frequency f = 22.235 GHz (6_16-5_23 transitioin) carried out on the 22-m Simeiz, 26-m HartRAO, and 26-m Torun radio telescopes are reported. The source has been episodically observed on the Simeiz telescope since 2000, with more regular observations beginning in 2017. A double flare was observed beginning in September 2017 and continuing to February 2018, which was the most powerful flare registered over the entire history of observations of this object. Most of the monitoring of the flare was carried out in a daily regime. Detailed analysis of the variations of the flux density, which reached a maximum value P ≈ 1.3 × 10^5 Jy, have led to important scientific conclusions about possible mechanisms for the emission in this water line. The exponential growth in the flux density in this double flare testifies that it was associated with a maser that was unsaturated right up to the maximum flux densities observed. An additional argument suggesting the maser was unsaturated is the relatively moderate degree of linear polarization (≈30%), nearly half the value displayed by the Galactic kilomasers in Orion KL. The accurate distance estimate for IRAS 18316-0602 (12.5 kpc) and the flux density at the flare maximum (≈1.3 × 10^5 Jy) makes this the most powerful Galactic kilomaser known. The double form of the flare with exponential rises in flux density rules out the possibility that the flare is the effect of directivity of a radiation beam relative to the observer. The physical nature of the flare is most likely related to internal parameters of the medium in which the maser clumps radiating in the water line are located. A rapid, exponential growth in the flux density of a kilomaser and associated exponential decays requires the presence of an explosive increase in the density of the medium and the photon flux, leading to an increase in the temperature by 10-40 K above the initial base level. A mechanism for the primary energy release in IRAS 18316-0602 is proposed, which is associated with a multiple massive star system located in a stage of evolution preceding its entry onto the main sequence. A flare in this object could initiate gravitational interaction between the central star and a massive companion at its periastron. The resulting powerful gravitational perturbation could lead to the ejection of the envelope of the central supermassive star, which gives rise to an explosive increase in the density and temperature of the associate gas-dust medium when it reaches the disk, where the maser clumps are located.

The article discusses the possibility of formulating a conclusion about the transition in early April 2009 to an exceptional state of the geophysical system in an area with a radius of about several hundred kilometers from Rome. This fact preceded the tragic earthquake on April 6, 2009, which led to large casualties in the Italian city of L'Aquila. This conclusion was obtained based on an analysis of the statistics of the critical frequency of the ionosphere. In the course of calculations, in particular, phenomena with a high degree of determinism that preceded the specified seismic event were detected. The fact of their existence with a high probability indicates the occurrence of an exclusive state of the regional geophysical system in the period of about several days before this event. It was depicted that the identified phenomena precede a significant number of seismic events. Based on the analysis of variations in the statistics of the critical frequency of the ionosphere in the Apennine region in 2007-2011, including those preceding the earthquake near the city of L'Aquila on April 6, 2009, an algorithm was formulated to detect a significant probability of transition to an exclusive state of the corresponding local segment of the geophysical system. The approach proposed in the article can be used to compile a short-term that is, calculated for the coming days, forecast of the existence of a significant probability of the occurrence of seismic events of large magnitude in various regions of the world.

Based on the long-term monitoring data of the water maser since 2019.0 to 2021.0 allowed us detecting in IRAS 16293-2422 two powerful phenomena lasted about year at radial velocities near 6 and 8 km s$^{-1}$. In both cases, powerful short flares were located on the tops of less powerful, but more prolonged ones (2.5 and 0.5 kJy), radiation of which initiated the emission of more powerful flares. For the first time, configurations of several emitting maser spots located at the line of sight to the observer were discovered experimentally. This made it possible to confirm the hypothesis of activation of the water maser, based on an increase in the amplification length of the maser due to several maser condensations located at the line of sight to the observer. The unsaturated state of the most powerful and shortest maser flares, as well as the saturated state of the weak, has been established. New important parameters of the water maser and the assumed location of the maser spots have been obtained., 12 pages, 5 pdf figures, uses jcappub.sty

Class II methanol masers are signs of massive young stellar objects (MYSOs). Recent findings show that MYSO accretion bursts cause flares of these masers. Thus, maser monitoring can be used to identify such bursts. Burst-induced SED changes provide valuable information on a very intense phase of high-mass star formation. In mid-January 2019, a maser flare of the MYSO G358.93-0.03 was reported. ALMA and SMA imaging resolved the core of the star forming region and proved the association of the masers with the brightest continuum source MM1. However, no significant flux rise of the (sub)mm dust continuum was found. Thus, we performed NIR imaging with GROND and IFU spectroscopy with FIFI-LS aboard SOFIA to detect possible counterparts to the (sub)mm sources, and compare their photometry to archival measurements. The comparison of pre-burst and burst SEDs is of crucial importance to judge whether a luminosity increase due to the burst is present and if it triggered the maser flare. The FIR fluxes of MM1 measured with FIFI-LS exceed those from Herschel significantly, which clearly confirms the presence of an accretion burst. The second epoch data, taken about 16 months later, still show increased fluxes. Our RT modeling yielded major burst parameters and suggests that the MYSO features a circumstellar disk which might be transient. From the multi-epoch SEDs, conclusions on heating and cooling time-scales could be drawn. Circumstances of the burst-induced maser relocation have been explored. The verification of the accretion burst from G358 is another confirmation that Class II methanol maser flares represent an alert for such events. The few events known to date already indicate that there is a broad range in burst strength and duration as well as environmental characteristics. The G358 event is the shortest and least luminous MYSO accretion burst so far., Comment: 22 pages, 11 figures, accepted by A&A. Abstract abridged for arxiv submission

In this work, scattering properties of a metal-dielectric structure are carried out in the optical range. In the proposed structure design, the absorption coefficient reaches more than 80% and has an almost constant character in the entire visible spectrum. Based on the obtained simulation results, such structures can be utilized in the field of solar energy storage applications. A review of works in the field of plasmonic solar cells is given, where the efficiency is usually increased due to the confinement of incident radiation in the active region of photoelectric conversion using localized modes, which are concentrated at the surface of conducting nanoparticles. That is, such batteries are operated in narrow wavelength intervals. However, in this article, the assumed solar cell efficiency enhancement can be achieved by incorporating the entire optical range due to the proposed metamaterial structure.

The results of long-term monitoring of the Galactic maser source IRAS 18316-0602 (G25.65+1.05) in the water-vapor line at frequency f = 22.235 GHz (616- 523 transitioin) carried out on the 22-m Simeiz radio telescopes are reported. The accurate distance estimate for IRAS 18316-0602 (12.5 kpc) and the flux density at the flare maximum ( ≈ 1.3 × 105 Jy) makes this the most powerful Galactic kilomaser known.

The paper discusses the results of the analysis of average characteristics of the geomagnetic field in the Crimea. Data for the analysis were calculated for the period from 1900 to 2014 through the International geomagnetic model IGRF-12. It is concluded that an increase in the total intensity of the geomagnetic field in Crimea with time in a northeasterly direction.

RT-22 radio telescope in Katsiveli (“Simeiz” VLBI station) is used extensively in international projects aimed at supporting spacetime reference systems for monitoring global changes on the Earth and for precise navigation in space. This paper discusses the results of the analysis of the data about the variations of the updates to the deformations of the Earth surface at Katsiveli site computed in terms of the “Atmosphere” model of a DFG (Deutsche Forschungsgemeinschaft) project. Significant oscillation with a one-year period is found in the Eastern and vertical components of the update vector to the deformations of the Earth surface at Katsiveli sit and the parameters of the sine model of this oscillation are computed.

The effects of regular solar and geodynamic oscillations in satellite data on the insolation of earth falling on the surface at Kara-Dag point for the period from 1983.5 to 2005.5 have been discovered. The parameters of the sinusoidal model of seasonal fluctuations are determined. Possible reasons for the increase in the amplitude of this oscillation are discussed. With the help of the wavelet transform, the spectral structure and spatial-temporal changes in the satellite data on the insolation of the incident on the earth's surface at Kara-Dag and local un modeled deformations of the earth at the point of Katsiveli were investigated. In the interferometric radio time series of observations of additions to the deformations of the earth's surface, carried out in the framework of international projects at the Simeiz station (Katsiveli), periodic components were found and modeled. The amplitude of the most significant seasonal component is 3.34 mm. Using the time-frequency wavelet transform, information was obtained on the temporal localization and changes in the power and frequency of seasonal fluctuations in the data on the insolation of the earth falling on the Kara-Dag point for the period from 1983.5 to 2005.5 and in the data on local un modeled deformations of the earth in paragraph Katsiveli for the period from 1980 to 2014.

Radio astronomy diagnostic complex based on the RT-22 radio telescope and three small radio telescopes combined into the KRIM Sun Service is located at 330 59 '30'' E longitude and 440 23 '52'' N latitude. The KRIM Sun Service conducts observations of the Sun in monitoring mode and alerts. The complex is integrated into the World Service for Solar Activity Research, and the daily data is stored in real time in digital form and posted on the sites of the World Sun Service, which includes 14 ground stations in cooperation with orbital observatories. During the minimum period of the 11-year solar activity cycle from September 6 to 10, 2017, KRIM Sun Service radio telescopes recorded a number of strong solar radio bursts in the active region NOAA 12673. The information obtained correlates well with data from other ground-based and satellite observatories, such as RSTN (Network Solar Radio Telescopes) and GOES (Geostationary Operational Satellite for Surrounding Space). This confirms the high quality and accuracy of the KRIM Solar Service radio telescopes.

Results of systematic observations of a sample of bright H2O maser sources with fluxes, on average, exceeding 200 Jy in their main spectral feature during April–September 2017 (G25.65+1.05, G25.825−0.178, G27.184−0.082, G34.403+0.233, G35.20−0.74, G43.8−0.13, G107.30+5.64) are presented. These observations were carried out in preparation for Very Long Baseline Interferometry observations with an array including the Crimean Astrophysical Observatory 22-m radio telescope. All these sources display fairly strong variability during the time interval considered, encompassing fluxes from ∼40 to ∼2300 Jy. A flare reaching ∼17 000 Jy was detected at a velocity of 42.8 km/s in G25.65+1.05 on September 7, 2017, which subsequently grew to 60 000 Jy at the end of September 2017. This suggests the presence of compact maser structures. The velocities covered by various spectral components range from 5 to 20 km/s. In three sources (G25.65+1.05,G25.825−0.178,G35.20−0.74), a general growth in the fluxes of all the spectral features is observed, which may indicate variations in the conditions for pumping by an external source, for example, variations in the infrared flux from a central source or the passage of a shock. Possible evidence for the presence of bipolar outflows or disk structures in G25.65+1.05 is discussed.

The modern automation system is unthinkable without the use of the accurate time source. Although most systems currently use the GPS signals, it is obvious that the GLONASS system will be used in the Russian Federation in the near future. The greatest interest in the existence of the GLONASS concerns the joint use of the GLONASS and the GPS. The time offset between the GPS and the GLONASS is an important parameter in the processing of combined GPS/GLONASS measurements. High-precision evaluation system of the time difference can provide centimeter accuracy positioning. The present paper concerns the analysis results for the variable component C1 of GLONASS timescale offset values relative to the scale UTC, TAI for the period of 2009-2013.

L ong series of multi-frequency monitoring data of the active galactic nucleus AO 0235+164, S0528+134 and S40954+658 from the radio to the gamma-ray are analyzed. Based on harmonic analysis of multi-frequency monitoring data we suggest that the observed harmonic components represent the precessional and orbital periods of a binary supermassive black holes (SMBH) system. The similarity of both the precessional and orbital periods in bright AGNs supports our hypothesis that, in all cases, we are observing emission from close binary systems consisting of SMBHs. The extremely compact size of the (less than 0.1 pc) may be a primary source of the powerful emission of the binary SMBH, which arises as a result of the dynamical losses due to the companion’s supersonic motion in the dense medium surrounding the orbit (10 9 − 10 10 ) cm −3 . The results obtained suggest that observed bright AGNs form a relatively rare population among massive elliptical galaxies, due to their narrowly directed emission and their short lifetimes.

The active core of the galaxy AO0235+164 is monitored in the optical and radio bands at millimeter wavelengths. Using the multifrequency data obtained in gamma, optical and radio bands, the characteristics of its radiation in the active phase of 2015–2016 are studied. The cross-correlation method was used to determine the delays of the 2015 flare that took place in AO0235+164 in different bands. The analysis made it possible to establish that, in comparison with the previous flare phenomena, changes in the orientation of the emissions (jets) have occurred. The angle θ between the jets and the direction towards the observer has decreased by a factor of $$\sqrt 2 $$ , resulting in a twofold increase in the γ-factor. The obtained value γ ≈ 40 is the most extreme value ever observed in AO0235+164 over the entire span of observations.

Data from long-term multi-frequency monitoring of the Active Galactic Nucleus (AGN) and blazar 3C 454.3 are analyzed. An unusually prolonged outburst in 2013–2017 had a duration that was twice the possible orbital period of the companion of the supermassive black hole (SMBH) located at the center of the host galaxy. It is proposed that the shape and duration of this outburst in 3C 454.3 could be the result of a coincidence between the plane of the accretion disk (AD) and the orbital plane of the companion. As a consequence, a prolonged energy release with enhanced intensity can be observed as the companion passes through the dense medium of the AD of the central SMBH. The presence of a 1.55-year orbital period in the variations of the emission of 3C 454.3 during this outburst also supports this hypothesis, as opposed to the possibility that the outburst was due to variations in γ and the Doppler factor. Small-scale flux-density fluctuations can arise during the outburst due to matter inhomogeneities with characteristic scales of about 1015 cm or more in the AD of the central SMBH and surrounding areas.

We investigate the prompt emission and the afterglow properties of short-duration gamma-ray burst (sGRB) 130603B and another eight sGRB events during 2012-2015, observed by several multiwavelength facilities including the Gran Canarias Telescope 10.4 m telescope. Prompt emission high energy data of the events were obtained by INTEGRAL-SPI-ACS, Swift-BAT, and Fermi-GBM satellites. The prompt emission data by INTEGRAL in the energy range of 0.1-10 MeV for sGRB 130603B, sGRB 140606A, sGRB 140930B, sGRB 141212A, and sGRB 151228A do not show any signature of the extended emission or precursor activity and their spectral and temporal properties are similar to those seen in case of other short bursts. For sGRB 130603B, our new afterglow photometric data constrain the pre-jet-break temporal decay due to denser temporal coverage. For sGRB 130603B, the afterglow light curve, containing both our new and previously published photometric data is broadly consistent with the ISM afterglow model. Modeling of the host galaxies of sGRB 130603B and sGRB 141212A using the LePHARE software supports a scenario in which the environment of the burst is undergoing moderate star formation activity. From the inclusion of our late-time data for eight other sGRBs we are able to: place tight constraints on the non-detection of the afterglow, host galaxy, or any underlying 'kilonova' emission. Our late-time afterglow observations of the sGRB 170817A/GW170817 are also discussed and compared with the sub-set of sGRBs.© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, AJCT acknowledges support from the Junta de Andalucia (Project P07-TIC-03094) and support from the Spanish Ministry Projects AYA2012-39727-C03-01 and 201571718R. This work has been supported by the Spanish Science Ministry 'Centro de Excelencia SeveroOchoa' Program under grant SEV-2017-0709. FEDER funds are acknowledged. E.S. acknowledges assistance from the Scientific and Technological Research Council of Turkey (TUBITAK) through project 112T224. We thank TUBITAK for a partial support in using T100 telescope with project number 10CT100-95. A.S.P acknowledges partial support grants RFBR 17-02-01388, 17-51-44018, and 1752-80139. E.D.M., A.A.V., and P.Yu.M. are grateful to RSCF grant 18-12-00522 for support. B.-B.Z. acknowledges support from National Thousand Young Talents program of China and National Key Research and Development Program of China (2018YFA0404204). R.Ya.I. is grateful for partial support by the grant RUSTAVELI/FR/379/6-300/14. R.S.R. acknowledges support from ASI (Italian Space Agency) through the Contract No. 2015-046R.0 and from European Union Horizon 2020 Programme under the AHEAD project (grant agreement No. 654215). SJ acknowledges the support of the Korea Basic Science Research Program through NRF-2015R1D1A4A01020961.

In 2017-18 the source of outstanding H2O maser bursts G25.65+1.05 have been intensively studied with a wide range of baselines - from compact array (JVLA) and ground VLBI (EVN, VLBA, KaVA) to space VLBI (RadioAstron mission supported by VLBA and EVN telescopes) - the report gives a brief summary of these observations.

Aims.We present our monitoring observations and analysis of water masers associated with W49N taken in 2017 and 2018. A significant flare occurred during these observations.Methods.We used ground-based radio telescopes in Simeiz (RT-22), Torun (RT-32), Medicina (RT-32), Effelsberg (RT-100) with broadband spectrometers. Observational data were collected and processed automatically.Results.We report a powerful flare of thev= +6 km s−1water maser feature; it increased in over ten months toS1.3 cm= 84 kJy in 2017 December, then decayed to the pre-flare quiescent value ofS1.3 cm= 8.7 kJy in 2018 August. We infer that this flaring feature is unsaturated based on the relationship between line width and flux density.

We performed a long-term optical (B, V, R bands), infra-red (J and K bands) and radio band (15, 22, 37 GHz band) study on the flat spectrum radio quasar, 3C 454.3, using the data collected over a period of more than 8 years (MJD 54500--57500). The temporal variability, spectral properties and inter-waveband correlations were studied by dividing the available data into smaller segments with more regular sampling. This helped us constrain the size and the relative locations of the emission regions for different wavebands. Spectral analysis of the source revealed the interplay between the accretion disk and jet emission. The source predominantly showed a redder-when-brighter trend, though we observed a bluer-when-brighter trend at high flux levels which could be signatures of particle acceleration and radiative cooling. Significant correlations with near-zero lag were seen between various optical/infra-red bands, indicating that these emission regions are co-spatial. Correlations with a time lag of about 10--100 days are seen between optical/infra-red and radio bands indicating these emissions arise from different regions. We also observe the DCF peak lag change from year to year. We try to explain these differences using a curved jet model where the different emission regions have different viewing angles resulting in a frequency dependent Doppler factor. This variable Doppler factor model explains the variability timescales and the variation in DCF peak lag between the radio and optical emissions in different segments. Lags of 6-180 days are seen between emissions in various radio bands, indicating a core-shift effect, Comment: 18 pages, 8 figures, 8 tables, accepted for publication in ApJ

Aims. A new method for determining the parameters of close double systems of supermassive black holes is proposed. Methods. We used the ground-based radio telescope in Simeiz (RT-22). Observational data were collected and processed automatically. Harmonic and wavelet data analyses were used to find the components of changes in the flux densities of 3C 454.3. Results. 3C 454.3 may be the most massive double system in the Universe. We show that when the bulk Lorentz (γ-factor) is taken into account, it is possible to obtain the agreed parameters of the 3C 454.3. We present first estimates of the size and thickness of the accretion disk of the 3C 454.3 obtained directly from the observation data. Based on the obtained data, we consider the characteristics of the gravitational radiation of this system, as well as the lifetime before merging, and possible variations in companion orbits.