Communications of the Byurakan Astrophysical Observatory (ComBAO)
Volume 70, Issue 1, July 2023

Introduction 0.1 MB
Editorial Board
Pages: 7-8



Byurakan Astrophysical Observatory: current status 0.3 MB
A. M. Mickaelian
Pages: 9-17
Abstract. We review the current activities and statuses of the Byurakan Astrophysical Observatory (BAO), one of the most active research institutes of the Armenian National Academy of Sciences. BAO was founded by the outstanding scientist, National Hero of Armenia Viktor Ambartsumian in 1946 as an institute of the Armenian Academy of Sciences. Its main scientific research field is the instability phenomena of the Universe. It is recognized as an Armenian National Value in 2013, IAU Regional Centre in 2015, IAU Outstanding Astronomical Heritage in 2021, Registered UNESCO documentary heritage item (Markarian Survey) in 2011 and has a number of other statuses. BAO has two major instruments; 2.6m classical reflector and 1m Schmidt telescope. A number of research projects are active at BAO and its scientists are rather active at international level. Since 1998, BAO bears the name of V. A. Ambartsumian.



Lyudwik Mirzoyan's life and activity 0.2 MB
V. Hambaryan and A. Akopian
Pages: 18-22
Abstract. Prof. Lyudwik Mirzoyan is one of the best representatives of the first generation of Armenian astronomers who had founded Byurakan Observatory and the Byurakan direction in science. For thirty years he had been the assistant of Victor Hambartsumian at Byurakan Observatory and has a huge input in formulation of the modern understanding of star formation, thus becoming the pioneer in Armenian observational astronomy.



Long-period fluctuations of solar active regions 0.1 MB
G. Dumbadze
Pages: 23-26
Abstract. The fluctuation spectra of solar active regions (ARs) contain information about the geometrical features and ground physical processes responsible for the appearance of such a background vibration noise. The investigation is based on an analysis of a time series built photospheric magnetograms and comprises case studies of several types of AR structures. We detect characteristic properties of Fourier and wavelet spectra evaluated for the solar active region area and radial magnetic flux time series. There are long-period oscillations, similarly to the characteristic lifetimes of super-granulation, determined from the datasets of the AR total area and radial magnetic flux, respectively. According to our results the fluctuation spectra of the AR areas and radial magnetic fluxes somewhat differ from each other both in terms of values of the spectral power-law exponents, as well as their variability ranges in different consider cases. The characteristic properties of the area and radial magnetic flux fluctuation spectra for the Ars show noticeable discrepancies between each other. It can also be concluded that behind the formation of AR area and radial flux vibration spectra might be different physical mechanisms in action.



Long-term variation of coronal holes latitudinal distribution 0.3 MB
D. A. Maghradze, B. B. Chargeishvili, D. R. Japaridze, N. B. Oghrapishvili, and K. B. Chargeishvili
Pages: 27-34
Abstract. We study the evolution of the latitudinal distribution of coronal holes using the Solar and Heliospheric Observatory (SOHO)/Extreme ultraviolet Imaging Telescope (EIT) 195 ˚Adata from 1996 May to 2020 April. To measure the presence of coronal holes at a given latitude, we use the presence factor, which estimates the length of an object along a given parallel, expressed as a percentage of half of the equator length. By semi-automatic processing of the data series, we obtained the 361 ×7346 latitude–time matrix. The corresponding diagram shows the significant difference in evolutionary shapes of a latitudinal distribution of non-polar and polar coronal holes. However, the morphology of the evolutionary picture and the migration route of the geometric centre of activity of the coronal hole in the diagram indicate that non-polar and polar coronal holes have the same driving mechanism. It is believed that the migration of the centre of activity of the coronal hole in the latitude–time diagram is a combination of two opposite migration paths. They intersect at the equator and diverge to opposite poles, where they form the so-called polar coronal holes, then again move to lower latitudes, and this happens cyclically. Determining the opposite migration paths by antiphase sinusoids, their deviation from antiphase determines the detected north–south asymmetry in the activity of the coronal hole.



Observations of Gaia Microlensing Events in Abastumani 0.2 MB
T. Kvernadze, O. Kvaratskhelia, and V. Kozlov
Pages: 35-42
Abstract. Gaia is now one of the most successful and leading transient space mission. It discovers nearly 2000 objects annually from all over the sky, down to about 20 mag, covering all possible classes of transients from supernovae and cataclismic variables to rare phenomena like microlensing events or pair-instability supernovae. The long time baseline of Gaia data allows for more robust detections of photometric anomalies. The gravitational microlensing method is especially sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars or black holes. The team, involved in the photometric follow-up observations of Gaia microlensing events, is collaborating with the International Working Group of Gaia Science Alerts through the BHTOM platform since 2020. Currently, we mainly use the 36-cm SCT-14 telescope of the Georgian National Astrophysical Observatory (Abastumani, Georgia) which is equipped with large format CCD and UBVRI filter set. At present we have processed and submitted for combined light curves observational data of 16 moderately bright Gaia alerts. Some of them clearly show the microlensing event type of light curves, though they need more detailed investigation. Here we present preliminary results of data connected with two such events: Gaia19dke and Gaia21dnc.



Search and identification of high-velocity stars by dynamical ejection and supernovae from multiple stars 0.1 MB
V. Hambaryan and R. Neuhaeuser
Pages: 43-48
Abstract. The project, funded by Science Committee of RA (ARPI program), intended to search, detection, kinematic study and identification of the birth places of the high-velocity and isolated neutron stars that encountered in the past with a stellar groups (multiple stars, stellar clusters, associations, etc.) closer than 10 pc, i.e. to test the concept: a high-velocity star and a stellar group or some of its members in the past were “in the same place at the same time”.
We plan to use stars with the high-quality astrometry and radial velocities from the very recently released Gaia DR3 catalogue and empirically select high-velocity candidates. Next, by using full gravitational potential of the Galaxy to calculate the motion of a stellar groups and a candidate of high-velocity star from their current positions to the proximity epoch. For numerical integration we will utilize the fast and accurate numerical integration.



New Herbig-Haro objects and outflows in the Dobashi 5001 dark cloud 0.1 MB
T. A. Movsessian and T. Yu. Magakyan
Pages: 49-53
Abstract. We present long-slit spectroscopy of some new Herbig-Haro objects and outflow systems discovered in the frames of Byurakan Narrow Band Imaging Survey (BNBIS) performed on 1 m Schmidt telescope of Byurakan Observatory. Spectroscopic observations were carried out with 6 m telescope (Russia) using SCORPIO2 spectral camera. All selected objects are associated with deeply embedded infrared sources in the molecular clouds. Long-slit spectroscopy allows to obtain position velocity diagrams of the emission structures like Herbig-Haro objects. Velocity fields of the outflows from IRAS 06277+1016 infrared source in Mon R1, from V963 Mon and 2MASS 06084223-0657385 in Mon R2 as well as from IRAS 06212-1049 are presented. Our spectroscopic data revealed bipolar outflow nature of the outflows associated with 2MASS 06084223-0657385 and IRAS 06212-1049.



Investigations of late-type giant stars from the First Byurakan Spectral Sky Survey 0.2 MB
G. R. Kostandyan, K. S. Gigoyan, and K. K. Gigoyan
Pages: 54-59
Abstract. We study late-type giants found in the First Byurakan Survey (FBS) data base. The third Gaia data release (Gaia EDR3) photometric and astrometric data have been used to characterize our sample of 1 100 M-type giants and 130 C-type stars found at high latitudes. Phase dependent light-curves from large sky area variability data bases such as Catalina Sky Survey (CSS) and The light curves from the Catalina Sky Survey (CSS), All-Sky Automated Survey for Supernovae (ASAS-SN) and Transiting Exoplanet Survey Satellite (TESS) databases were exploited to study their variability nature. Using TESS light curves, the variability types of some objects have been established for the first time.



TYC 1417-891-1 and TYC 1478-742-1: Eclipsing Variable Stars. The Gaia EDR3 and TESS Photometric Data 0.2 MB
K. K. Gigoyan, K. S. Gigoyan, and G. R. Kostandyan
Pages: 60-67
Abstract. Based on the TESS (Transiting Exoplanet Survey Satellite) phase dependent light curves, we confirm the eclipsing type variability nature for two G – type dwarfs: TYC 1417-891-1 and TYC 1478-742-1. Both objects show EA (Algol – type) light curves morphology. Orbital period for TYC 1417-891-1 is P ≈ 8.0 day and for TYC 1478-742-1, P ≈ 13.6 day. We present Gaia EDR3 and TESS catalogue important physical parameters as well as LAMOST spectra. Both objects are relatively bright and are located at a distance of 260.59 (±3.21) pc (TYC 1417-891-1) and 117.42 (±0.74) pc (TYC 1478-742-1). The TESS light curve of TYC 1478-742-1 show also flares as well. We discuss possible nature of the secondary and faint objects around these stars.



Multiwavelength search and studies of active galaxies 0.2 MB
A. M. Mickaelian, H. V. Abrahamyan, G. M. Paronyan, G. A. Mikayelyan, R. R. Andreasyan, A. G. Sukiasyan, L. A. Hambardzumyan, and V. K. Mkrtchyan
Pages: 68-76
Abstract. We review the field of active galaxies (both AGN and Starbursts) focusing on their multiwavelength search and studies at the Byurakan Astrophysical Observatory (BAO). Many famous historical surveys carried out in Byurakan are known and many more are active and ongoing. We give examples of studies in optical wavelengths, IR, radio and X-ray, as well as multiwavelength studies. The studies are characterized by multiwavelength approach to statistical analysis of large amount of data obtained in different wavelengths. Results on HRC/BHRC sample objects (optical identifications of ROSAT X-ray sources), studies of Markarian galaxies in UV and multiwavelength SEDs, abundance and star formation determinations in Mrk galaxies from SDSS spectra, revised optical classification of “LINERs”, study and classification of SDSS spectra for Byurakan-IRAS Galaxies, summary of observations and study of Byurakan-IRAS Galaxies (BIG objects), discovery of new bright ULIRGs from the IRAS PSC/FSC Combined Catalogue and their spectral classification, radio variable sources at 1400 MHz and their optical variability, classification of BZCAT objects having uncertain types (BZU objects), and optical variability of blazars are presented. At the end, we briefly present our new fine classification of active galaxies based on all our previous studies.



A study of active galaxies in groups of galaxies and in the field 0.2 MB
R. R. Andreasyan, S. A. Hakopian, A. P. Mahtessian, H. V. Abrahamyan, G. M. Paronyan, and A. G. Sukiasyan
Pages: 77-82
Abstract. We study regions with radius of 500 pc around of the central radio galaxies from our sample. For this study were chosen about 30 nearby 3C radio galaxies of different FR types. We bring the maps of optical galaxies that are overlaid on the radio map of 3C radio source. It was used also the maps of these regions in all available wavelength. Here we present more detail analyses and new results for the radio galaxy of FRI type 3C31.
The dependencies of the morphological types of the first and second ranked group galaxies on the magnitude gap were studied. It is shown that there is no increase in the relative number of elliptical galaxies among the first and second ranked group galaxies with large magnitude gaps. Some results are presented on studies of a sample of about hundred galaxies (“100SBS”) from two adjacent fields of SBS, which have spectral data in SDSS. Comparative analysis was done between two classifications that the 100SBS objects got - from one side Starburst or Starforming in SDSS, from the other - SfGcont and SfGneb, with a possibility of further detailing in accordance to our scheme for star-forming galaxies.



Classification of Blazars by Activity Types 0.1 MB
H. V. Abrahamyan, A. M. Mickaelian, G. A. Mikayelyan, G. M. Paronyan, A. G. Sukiasyan, V. K. Mkrtchyan, L. A. Hambardzumyan
Pages: 83-87
Abstract. Blazars are the most energetic sources in the Universe. They unify two major types of objects: BL Lac objects and Flat Spectrum Radio Quasars (FSRQ). So far, 3561 blazars are known from BZCAT v.5 catalogue. However, in BZCAT v.5 all blazars are grouped into four main classes, where extended radio sources and some unknown objects are added: BZB (BL Lac objects), BZQ (FSR Quasars), BZG (Blazar-like (BZQ-like) Galaxies) and BZU (Blazars of Unknown subtypes). There is no information about optical classification of these sources. We have accomplished optical classification for BZU and BZG sources, which have optical spectra from SDSS catalogue. Most of these sources had no optical class before or have changed their optical classification after our work. For some blazars, we obtained optical classes for the first time. In the current work we have done an overall optical investigation for all classes of blazars (BZB, BZQ, BZG and BZU). After the optical classification, some BZU sources, which have SDSS spectra, have changed to QSO (BZQ) or Galaxies (BZG). This way we give a better understanding of objects included in BZCAT v.5.



X-ray Properties of Radio Galaxies from the NVSS List 0.2 MB
G. M. Paronyan, A. M. Mickaelian, H. V. Abrahamyan, G. A. Mikayelyan, A. G. Sukiasyan, L. A. Hambardzumyan, and V. K. Mkrtchyan
Pages: 88-93
Abstract. An identification of radio sources from the NVSS list with ROSAT X-ray sources was made as well as also with optical objects from SDSS DR 16. We have tried to find the connection between the fluxes of different wave ranges, for different types of objects. We also have tried to find the relationship between the sizes and polarization angles of sources with the types of objects and recurrence. The fluxes detected from X-ray, optical, and radio bands for them are compiled. This database allows an investigation on broad band energy distribution and other possible correlations among spectral indices and luminosities for various types of extragalactic objects.



BL Lacertae: dynamics of a quasi-stationary feature in the inner part of a relativistic jet 0.3 MB
L. A. Hambardzumyan, T. G. Arshakian, and A. B. Pushkarev
Pages: 94-99
Abstract. Radio interferometric VLBA observations allow the mapping of relativistic jets with sub-milliarcsecond resolution, which enables the studying of the fine structure and dynamics of the jets in active galactic nuclei. A quasi-stationary component (QSC) near the radio core is observed in a number of blazars. VLBA monitoring of the BL Lacertae object at 15 GHz has shown that the QSC located at about 0.26 mas from the radio core is followed by superluminal components, whose dynamics forms the structure of the jet on parsec scales. We study the trajectory of the QSC using the 164 epochs taken from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) database. The trajectory of the QSC is complex, and we use a moving average smoothing filter to track the intrinsic motion of the QSC. At small time scales of few months, we find that the QSC makes a swinging motion with about 23 reversals over 20 years with an average period of about 0.5 years. The trajectories between the reversals have varying lengths with a mean value of about 30 μas (∼ 0.04 pc) and curvatures of varying degrees. Number of clockwise reversals are about twice less than that of anticlockwise reversals.



The discrepancy between the values of the Hubble constant and the effect of dark energy on baryonic matter 0.1 MB
H. Harutyunian
Pages: 100-105
Abstract. It seems clear that researchers have not yet fully appreciated the true implications of the discovery of dark energy for understanding evolutionary processes in the baryonic universe. Based on general physical considerations, we consider here the influence of dark energy on baryon objects at the level of atomic nuclei and elementary particles. For such an analysis, the concept is adopted, according to which the entire baryonic Universe interacts with dark energy on all cosmic scales. The consequences seem quite dramatic, since the accumulation of energy in the baryon world changes the energy balance and reduces the binding energy of all objects, including atomic nuclei. Consequently, the nuclear mass defect decreases, their mass increases, and both effects make the nuclei more and more unstable. This leads to the destabilization of all nuclei and their gradual transfer to the stage of radioactive decay, which increases over time the relative amount of light elements, including hydrogen. Evolution under the influence of dark energy, on the other hand, increases the masses of atomic nuclei. We have used this hypothetical effect to interpret the so-called ”Hubble tension” paradox. This also makes it possible to estimate the growth of the proton mass due to dark energy.



Cosmological scalar field 𝝓CDM models 2.8 MB
O. Avsajanishvili
Pages: 106-113
Abstract. Cosmological models that go beyond the standard Lambda Cold Dark Matter (ΛCDM) scenario, namely, scalar field ϕCDM models, are considered. The Hubble expansion rate of the universe, the dynamic and the energetic domination of dark energy, the formation of matter density fluctuations and the large-scale structure growth rate in these models compared to the standard spatially-flat ΛCDM model are investigated.



Dependence of standardization parameters of type Ia supernova light curves on redshift 0.3 MB
A. P. Mahtessian, G. S. Karapetian, M. A. Hovhannisyan, and L. A. Mahtessian
Pages: 114-122
Abstract. The paper shows that the parameters X1 and C used to standardize the luminosity of type Ia supernovae in the SALT2 model are highly dependent on redshift. This leads to the fact that during standardization, with increasing z, the average absolute stellar magnitude of type Ia supernovae artificially increases and, therefore, for a given apparent magnitude, we attribute to them, on average, a greater distance than they actually have. And therefore, it is believed that they are receding with acceleration. Therefore, such standardization is unsuitable for measuring distances to type Ia supernovae. If the standardization parameter (−αX1 + βC) is replaced by the redshift-dependent parameter (εz), then the parameter ΩΛ turns into 0 in the ΛCDM model.



Evolutionary stages of the universe 0.2 MB
R. Natsvlishvili
Pages: 123-130
Abstract. The matter from which the Metagalaxy is formed is constantly changing, evolving. Since the speed of propagation of the electromagnetic wave in space is not instantaneous, it is limited, within the capabilities of existing powerful telescopes, we can observe the forms of matter in different stages of the evolution of the Metagalaxy in chronological order. So, the more distant the form of matter in the Metagalaxy, the earlier, or younger, it is. In this article, we tried to characterize the stages of the Metagalaxy evolution from a dynamic point of view. In the case of such a model of the Universe, quasars are objects of earlier stage of the evolution of galaxies, and blazars are objects of an intermediate stage between quasars and galaxies.



The Spectral Lines Evolution in the Presence of Time-Dependent Energy Sources 0.4 MB
A. G. Nikoghossian
Pages: 131-142
Abstract. A brief review of the author’s recent work on the development and application of the theory of time-dependent transfer of radiation in the spectral line is given. Various factors that influence the temporal characteristics of changes in line spectra are studied. This creates a fundamental opportunity to use them to gain insight into both external energy sources, the physical and geometrical properties of the medium itself as well as the various optical parameters of the observed spectral lines.



Of the new opportunity of solving the Ambartsumian’s functional equation in the theory of radiative transfer 0.1 MB
H. V. Pikichyan
Pages: 143-151
Abstract. A new approach to solving of the Ambartsumian’s functional equation is presented. Its application is illustrated on the two classical cases: a) in the case of a plane-parallel semi-infinite medium with monochromatic anisotropic scattering and b) the simple one-dimensional problem of diffuse reflection of radiation from the scattering-absorbing semi-infinite medium in the case of the general law of redistribution of radiation by frequencies. The desired: a) azimuthal harmonics of reflection function dependent on two angular variables are explicitly expressed through the according eigenfunctions of one angle variable and b) diffuse reflection function of two frequency variables also expressed through a system of according eigenfunctions which have only one frequency variable. This does not require the use of any simplifying assumptions or special decompositions of the characteristics of elementary act of scattering: a) of scattering indicatrix and b) of the redistribution function of radiation by frequencies.



The essence of onset and self-sustenance of turbulence in astrophysical shear flows 0.4 MB
M. Kavtaradze, G. Mamatsashvili, and G. Chagelishvili
Pages: 152-164
Abstract. To understand the mechanism of the self-sustenance of subcritical turbulence in spectrally stable astrophysical (constant) shear flows, we performed direct numerical simulations of turbulence in plane hydrodynamic and MHD homogeneous shear flows in the local shearing-box approximation with subsequent analysis of the dynamical processes in spectral/Fourier space. In the MHD case, we considered uniform magnetic field directed parallel to the flow. There are no exponentially growing modes in such flows and the turbulence is instead energetically supported only by the linear transient growth of Fourier harmonics of perturbations due to the shear flow non-normality. This non-normality-induced growth, also known as nonmodal growth, is anisotropic in Fourier space, which, in turn, leads to a specific anisotropy of nonlinear processes in this space. As a result, a main nonlinear process in shear flows is transverse (angular) redistribution of harmonics in Fourier space – nonlinear transverse cascade – rather than usual direct or inverse cascades. It is demonstrated that the turbulence is sustained by a subtle interplay between the linear nonmodal growth and the nonlinear transverse cascade for all considered flow configurations. The only energy supplier for the turbulence is the linear transient growth of perturbations due to the flow shear, which is mediated by Reynolds and Maxwell stresses, extracting, respectively, kinetic and magnetic energy from the background flow – the nonlinear processes do not directly change the total perturbation energy but only redistribute it among Fourier harmonics of perturbations. We propose the basic cycles of the turbulence sustenance in the considered cases, which clearly show the synergy of linear and nonlinear processes in the self-organization of the flow. Performing numerical simulations for different values of the background magnetic field, we show that with the increase of the field, the onset of turbulence occurs at larger times and the power of turbulence reduces. Finally, at definite threshold background magnetic field the flow completely stabilizes. It is significant that, there is an essential difference in the energy supply of plane and rotating/Keplerian astrophysical shear flows: in plane shear flows the leading linear process energetically supplying turbulence is due to the kinematics (Reynolds stress), while for Keplerian rotation – is due to magnetic field (Maxwell stress).



Iron in Armenian really means a Sky Drop? 0.2 MB
A. Yeghikyan
Pages: 1-6
Abstract. In the languages of the ancient Hittites and Egyptians, and later the Greeks, iron was called celestial metal or by the close in meaning word. A browse review of iron names in several languages shows that with the exception of the mentioned three languages, in other languages the name of the iron reflects its function (hard, cutting, superpower, iron-stone, etc.) but not origin. According to the Hittite sources, iron was produced by the masters of the Hatti kingdom controlled by Hittities, located, by the way, next to the kingdom of Hayasa. Hatti adjoins the region on the southeastern coast of the Black Sea, where, according to Aristotle, the Halibs lived - craftsmen who produced the best iron. It is known that the mountain rivers of this area brought sand and accumulated in the mouths sand with a high content of magnetite, an iron-containing mineral with a lower melting point (compared to other rocks). It is this circumstance, according to geologists, that the beginning of the iron century takes place in this area in the XV-XIII centuries BC. On the basis of all of the above, the literal translation of the Armenian name of iron erkat = dropped from the sky does not seem to be meaningless. But academic philologists categorically disagree with this. In this report, a more convincing (from the astrophysicist point of view) etymology of the Armenian word erkat = er-ka = heavenly metal is proposed.