Communications of the Byurakan Astrophysical Observatory (ComBAO)
Volume 68, Issue 2, December 2021
Introduction 0.2 MB
Discovery and studies of stellar associations. The Key to Understanding Star Evolution 0.2 MB
A. A. Akopian
Abstract. The review presents works carried out in BAO in the period 1947-70. It tells about the history and significance of one of the greatest discoveries of the twentieth century - stellar associations. Among the fundamental works of Ambartsumian and BAO studies of stellar associations occupy a special place. Their discovery radically changed the existing theories of star formation and evolution and "revived" the slowly dying (as previously assumed) Universe. The discovery of stellar associations proved that star formation occurs in our era. Ambartsumian's ideas clarified the existing and somewhat confusing theory of stellar evolution and gradually became one of the generally accepted directions of the theory of stellar evolution. For more than 75 years, scientists from the BAO and many observatories around the world have been studying stellar associations, but surprises and discoveries are not exhausted. Metaphorically, one can say that for a long time astronomers will follow the path illuminated by stellar associations.
Statistical studies of flare stars and other flashing objects carried out at the Byurakan Observatory 0.3 MB
A. A. Akopian
Abstract. The review briefly presents the statistical studies of flare stars and related objects carried out at the Byurakan Astrophysical Observatory, in particular: i) determination of the evolutionary status of flare stars, ii) an explanation of the observed difference between flare stars of the galactic field (type UV Cet) and flare stars of systems (open clusters, associations), iii) the connection between flare stars and T Tauri stars, iv) short-term and long-term (evolutionary) variability of flare activity, v) original statistical methods developed for the study of flare stars and their systems, vi) recent advances in research on flashing objects. This review does not present such important areas of research on flare stars as the determination of physical parameters, photometry and colorimetry of stars and their flares, detailed studies of individual stars, theoretical works on possible mechanisms of flares. These areas were well presented in many books and reviews by Ambartsumian and Mirzoyan.
Search and Studies of the First Byurakan Survey Blue Stellar Objects 0.2 MB
A. M. Mickaelian, G. A. Mikayelyan, H. V. Abrahamyan, and G. M. Paronyan
Abstract. The First Byurakan Survey (FBS) 2nd Part was devoted to search and studies of Blue Stellar Objects (BSOs) and Late-type Stars. Eleven lists of 1103 BSOs were published in Astrophysics in 1990-1996, found in FBS low-dispersion spectroscopic plates. The selection was carried out in the region with +33◦ > δ > +45◦ and δ >+61◦ with a surface of ∼4000 deg2. As a result, the catalogue of the FBS BSOs was compiled. Its preliminary version has been available at CDS since 1999. We revised and updated the FBS BSOs catalogue with the new data from recently published optical and multiwavelength catalogues to give access to all available data and make further comparative studies of the properties of these objects possible. We made cross-correlations of the FBS BSOs catalogue with the MAPS, USNO-B1.0, SDSS, and 2MASS, as well as ROSAT, IRAS, NVSS, and FIRST catalogs, added updated SIMBAD and NED data for the objects, and provided accurate DSS1 and DSS2 positions and revised photometry. We also checked the objects for proper motion and variability. A refined classification for the low-dispersion spectra in the Digitized First Byurakan Survey (DFBS) was carried out. The revised and updated catalogue of FBS blue stellar objects contains 1101 objects. The FBS blue stellar objects catalogue can be used to study a complete sample of white dwarfs, hot subdwarfs, HBB stars, cataclysmic variables, bright AGN, and to investigate individual interesting objects.
Markarian survey and Markarian galaxies 0.9 MB
A. M. Mickaelian
Abstract. Markarian survey (or the First Byurakan Survey, FBS) was the first systematic survey for active galaxies and was a new method for search for such objects. Until now, it is the largest objective prism survey of the sky (17,000 deg2). It was carried out in 1965-1980 by B. E. Markarian and his colleagues and resulted in discovery of 1517 UV-excess (Markarian) galaxies. They contain many active galaxies, as well as powerful gamma-, X-ray, IR and radio sources (Mrk 180, 231, 421, 501, etc.), BCDGs (Mrk 116) and interacting/merging systems (Mrk 266, 273, etc.). They led to the classification of Seyfert galaxies into Sy1 and Sy2 and the definition of Starbursts (SB). Several catalogs of Markarian galaxies have been published (Bicay et al., 1995, Markarian et al., 1989, Mazzarella & Balzano, 1986, Petrosian et al., 2007) and they are accessible in all corresponding databases. Markarian survey also served as a basis for search for UVX stellar objects (including QSOs and Seyferts), late-type stars and optical identification of IR sources. At present the survey is digitized and DFBS database is available. We review the main characteristics of the Markarian survey, its comparison with other similar surveys and the importance of Markarian galaxies in modern astrophysics.
Theoretical Astrophysics in the Byurakan Observatory (1946 - 2021) 0.7 MB
Abstract. The purpose of this review is to give a general idea of the results on theoretical astrophysics investigations carried out at the Byurakan Observatory during the period of its existence. A special place in the review is given to the research work in the Department of "Theoretical Astrophysics", founded in 1965. The review consists of two parts. The first part is mainly devoted to works on the theory of radiation transfer somehow related to Ambartsumian's ideas developed in his fundamental studies of the 40-50s of the last century. The second part presents, on the one hand, the results which are of importance for theoretical physics in general and, on the other hand, gives their application to the interpretation of observational data of various cosmic objects. In order to get an idea of the importance of each result, the background and prerequisites of the research are given, indicating its significance from the point of view of astrophysics. Naturally, the most important results are presented in more detail. At the same time, the review in one way or another includes almost all of the most important results obtained by various members of the department at different times. It should be noted that works on some other areas of theoretical astrophysics are not included in the review, since they are presented in other reviews of this series.
Ambartsumian’s vision and further insight to key puzzles of ultra-high energy astrophysics 1.3 MB
Abstract. We review the Ambartsumian’s cosmogony, which involves his fundamental ideas on Stellar Associations and eruptive Activity of Galactic Nuclei, where the creation process is at work. Itis caused by the violent outburst events of transformations of superdense matter in supermassive compact bodies in galaxies, away from the accretion physics. We discuss the pioneering works of V.A. Armbartsumyan and G.S. Saakyan carried out at Byurakan Observatory in the earlier of 1960’s towards the physics of equilibrium configurations of degenerate superdense gas of elementary particles, particularity, the hyperon configurations of stellar masses. These issues have been comprehensively developed later on by G. Ter-Kazarian in the proposed theory of distortion of space-time continuum(DSTC) at huge energies (respectively, at short distances < 0.4fm), which underlies the microscopic theory of black hole (MTBH). The MTBH has further proved to be quite fruitful for ultra-high energy astrophysics. The MTBH explores the most important process of spontaneous breaking of gravitation gauge symmetry at huge energies, and thereof for that of re-arrangement of vacuum state. As a corollary, MTBH has smeared out the central singularities of BHs, and makes room for their growth and merging behavior, with implications of vital interest for high energy astrophysics.
A new look at some aspects of geometry, particle physics, inertia, radiation and cosmology 0.8 MB
Abstract. Continuing along the line of our previous report (Ter-Kazarian, 2021a), in present communication we briefly outline several closely related issues, carried out also in Byurakan Astrophysical Observatory, not touched in it for brevity reasons. These issues reveal and further develop novel aspects of the fundamental nature and structure of the space-time geometry and the high energy physics, the inertia effects, the intense radiation physics, and the notion of relative velocity in a curved space-time.
The Digitized First Byurakan Survey (DFBS) as UNESCO Documentary Heritage 0.6 MB
A. M. Mickaelian, L. A. Sargsyan, G. A. Mikayelyan, K. S. Gigoyan, R. Nesci, C. Rossi
Abstract. The famous Markarian Survey (or the First Byurakan Survey, FBS) was carried out in 1965-1980. Its 2000 plates were digitized in 2002-2007 and the Digitized FBS (DFBS, www.aras.am/Dfbs/dfbs.html) was created. New science projects have been conducted based on this low-dispersion spectroscopic material. The Armenian Virtual Observatory (ArVO, www.aras.am/Arvo/arvo.htm) database accommodates all new data. The project was conducted in collaboration with the Italian, USA and German scientists, as well as the Armenian Institute of Informatics and Automation Problems (IIAP) and continued during 6 years in 2002-2007. Markarian Survey and its digitized version were included in UNESCO Documentary Heritage “Memory of the World” International Register in 2011 as one of the rare heritage items from science.
Twenty years of the Armenian Astronomical Society (ArAS) 0.4 MB
A. M. Mickaelian, S. V. Farmanyan, and G. A. Mikayelyan
Abstract. A review on the activities and achievements of the Armenian Astronomical Society (ArAS) and the Armenian astronomy in general is given on the occasion of the 20th anniversary of the official foundation of ArAS. ArAS membership, ArAS electronic newsletters (ArASNews), ArAS webpage, Annual Meetings, Annual Prize for Young Astronomers (Yervant Terzian Prize) and other awards, international relations, participation in international organizations, Byurakan International Summer Schools (BISS), regional and local schools, Byurakan science camps, astronomical Olympiads and other events, other matters related to astronomical education, astronomical heritage, amateur astronomy, astronomy outreach and ArAS further projects are described and discussed.
Outline of Calendar Studies Conducted at the Byurakan Astrophysical Observatory in 1983-2021 0.7 MB
H. A. Malkhasyan
Abstract. The calendar studies conducted at the Byurakan Astrophysical Observatory in 1983-2021 are the result of Grigor Broutian’s initiation and scientific activity. The approaches used by him have raised a number of new issues and provided extremely important results that are a serious incentive for the future development of this multilayered and multifaceted field in terms of astronomy and historical culture. Almost all the problems of the Armenian and adjacent calendars of the Christian period have been discussed and finally resolved. The Armenian calendar attributed to Hayk Nahapet has been thoroughly researched and brought to an astronomically grounded comprehensive solution. The preliminary, so-called Protohaykian calendar has been revealed with its main and key aspects, and received astronomical as well as archaeological real evidence. All in all, in general the 11,000- year-old Armenian calendar-astronomical traditional historical culture has been deciphered in its continuity. Some new data have been obtained in favor of the existence of an earlier, the so-called “Initial Calendar” as well. Moreover, common close relations have been revealed in the field of natural-philosophical-religious and their historical-cultural-astronomical traditional perception of the creation of the ancient Armenian “Vishap” (“dragon”) stone monuments, the “Zorats Qarer” megalithic ensemble, the “Sasnay Tsrer” (Daredevils of Sassoun) epic poem, the Armenian folk tales and archaeological materials.
The synchrotron mechanism and the high energy flare from PKS 1510-089 0.3 MB
Z. N. Osmanov
Abstract. In order to understand the role of the synchrotron emission in the high energy gamma-ray flares from PKS 1510-089, we study generation of the synchrotron emission by means of the feedback of cyclotron waves on the particle distribution via the diffusion process. The cyclotron resonance causes the diffusion of particles along and across the magnetic field lines. This process is described by the quasi-linear diffusion (QLD) that leads to the increase of pitch angles and generation of the synchrotron emission. We study the kinetic equation which defines the distribution of emitting particles. The redistribution is conditioned by two major factors, QLD and the dissipation process, that is caused by synchrotron reaction force. The QLD increases pitch angles, whereas the synchrotron force resists this process. The balance between these two forces guarantees the maintenance of the pitch angles and the corresponding synchrotron emission process. The model is analyzed for a wide range of physical parameters and it is shown that the mechanism of QLD provides the generation of high energy (HE) emission in the GeV energy domain. According to the model the lower energy, associated with the cyclotron modes, provokes the synchrotron radiation in the higher energy band.
Introduction 0.1 MB
The Impact of Eruptions from Young Stars on Environments of Rocky Exoplanets 0.2 MB
V. S. Airapetian
Abstract. Kepler and TESS missions have discovered over 4500 extra solar (exoplanets) around F, G, K and M dwarfs. They also revealed frequent superflares on planet hosting stars, providing a mechanism by which host stars may have profound effects on the physical and chemical evolution of exoplanetary atmospheres. While we can only infer the course of the Sun’s early evolution and how it might have affected the early evolution of the Earth, possibly setting the stage for the origin of life, the observation of planets around sun-like stars allows us to directly observe events which likely took place in our own solar system. A major question this leads to is: what effects do extreme energy fluxes from eruptive events during evolution of G-K planet hosts have on prebiotic chemistry and primitive life forms on primitive planets? To address this question, I will describe recent observations of young solar-like stars as inputs for our 3D MHD models of the corona, the wind and transient events (flares, coronal mass ejections and solar energetic particle events) and discuss their impact on atmospheric erosion and chemistry of our planet. I will then use these constrained energy fluxes to describe our recent atmospheric chemistry models impacted by energetic particles from the young Sun and formation and precipitation of biologically relevant molecules. I will then highlight our results of laboratory experiments of proton irradiation of mildly reduced gas mixtures and their implications to the climate, prebiotic chemistry and the rise of habitability on early Earth and young exoplanets.
Narrow band imaging survey of dark clouds 0.8 MB
T. A. Movsessian, T. Yu. Magakyan, S. N. Dodonov, and H. R. Andreasyan
Abstract. We present new results obtained in frames of the Byurakan Narrow Band Imaging Survey (BNBIS). Observations were carried out with upgraded 1 m Schmidt telescope of Byurakan Observatory. Main task of this survey is to search and to study the new Herbig-Haro objects and collimated outflows using narrow-band Hα and [S ii] images of some fields in dark clouds of Galaxy. And, because, Herbig-Haro objects are the main indicators of active starformation processes to fined regions where going on active starformation processes. Main targets of this survey are R associations, young stellar objects associated with compact reflection nebulae, but here we will mainly focused on deeply embedded infrared sources in molecular clouds. During this survey we plan to significantly expand the list of HH objects by using the high quantum efficiency of the system and the telescopes high focal ratio (F/2), which allows detecting low surface brightness objects as well as large field of view of Schmidt telescope.
Study of radio properties of active galaxies 0.9 MB
H. V. Abrahamyan, A. M. Mickaelian, G. M. Paronyan, G. A. Mikayelyan, and A. G. Sukiasyan
Abstract. In this paper we investigate radio properties of active galaxies taken from Veron-Cetty & Veron (2010) catalogue. The galaxies are limited to magnitudes in the range of 12m-19m. We have cross-correlated the list with radio catalogues and selected those galaxies, which have data on 5 radio fluxes at different wavelengths. For all the objects we have built radio spectra and estimate radio spectral indices. As a result, we have αaverage±0.5036±0.0717.
Composition of super-Earths, super-Mercuries, and their host stars 0.3 MB
V. Adibekyan, N. C. Santos, C. Dorn, S.G. Sousa, A. A. Hakobyan, B. Bitsch, Ch. Mordasini, S. C. C. Barros, E. Delgado Mena, O. D. S. Demangeon, J. P. Faria, P. Figueira, B. M. T. B. Soares, and G. Israelian
Abstract. Because of their common origin, it was assumed that the composition of planet building blocks should, to a first order, correlate with stellar atmospheric composition, especially for refractory elements. In fact, information on the relative abundance of refractory and major rock-forming elements such as Fe, Mg, Si has been commonly used to improve interior estimates for terrestrial planets. Recently Adibekyan et al. (2021) presented evidence of a tight chemical link between rocky planets and their host stars. In this study we add six recently discovered exoplanets to the sample of Adibekyan et al and re-evaluate their findings in light of these new data. We confirm that i) iron-mass fraction of rocky exoplanets correlates (but not a 1:1 relationship) with the composition of their host stars, ii) on average the iron-mass fraction of planets is higher than that of the primordial f star iron , iii) super-Mercuries are formed in disks with high iron content. Based on these results we conclude that disk-chemistry and planet formation processes play an important role in the composition, formation, and evolution of super-Earths and super-Mercuries.
On the origin of runaway binaries: the case of the HMXB 4U 2206+54/BD +53 2790 0.2 MB
V. Hambaryan, K. A. Stoyanov, M. Mugrauer, R. Neuhäuser, W. Stenglein, R. Bischo, K.-U. Michel, M. Geymeier, A. Kurtenkov, and A. Kostov
Abstract. We present most probable place and time of the origin of the runaway high-mass X-ray binary 4U 2206+54 based on its Gaia EDR3 astrometric parameters and our new systemic radial velocity. We studied the trace back motion of the system and propose that it originated in the subgroup of the Cepheus OB1 association (Age∼4-10 Myr) with its brightest star BD+53 2820 (B0V; L∼104.7L⊙). The kinematic age of 4U 2206+54 is about 2.8 ± 0.4 Myr, it is at a distance of 3.1-3.3 kpc and has a space velocity of 75-100 km/s with respect to this member star (BD+53 2820) of the Cep OB1 association. This runaway velocity indicates that the progenitor of the neutron star hosted by 4U 2206+54 lost about 4-9M⊙ during the supernova explosion and the latter one received a kick velocity of at least 200-350 km/s. The high-mass X-ray binary 4U 2206+54/BD+53 2790 was born as a member of a subgroup of the Cep OB1 association, the initially most massive star in the system terminated its evolution within ≲ 7 − 9 Myr, corresponding to an initial mass ≳ 32 M⊙.
Perseverance Rover and Its Search for Life On Mars 0.3 MB
J. L. Green
Abstract. Mars orbiters, landers, and rovers have made extraordinary discoveries about the evolution of Mars and its potential for life. At this time, it is clear, that the potential of ancient life on Mars has increased based on several discoveries. There have been many observed signs of ancient liquid water: surface and underground. There are past geological environments on Mars that had reasonable potential to have preserved the evidence of life, had it existed. The detection of complex organics by Curiosity has increased the potential for preserving “fingerprints of life” that may be locked away in the rock record. These and other factors have led NASA, with the support of other space agencies, to mount a Mars sample return (MSR) campaign. The first mission of MSR is the Perseverance rover. Designed to core and store rock, soils, and atmospheric samples in sealed tubes for later return, Perseverance landed in Jezero crater in February 2021 near an extensive ancient river delta. Other missions will follow to bring these samples back to Earth for further analysis. In addition, Perseverance carried the Ingenuity helicopter as a technology demonstration which has been tremendously successful and may lead to other future ariel missions on the red planet.
On the Magnetic Fields of Galaxies 1.0 MB
R. R. Andreasyan
Abstract. We bring results of some our investigations of magnetic field of our Galaxy and extragalactic radio sources. For the study were used data of Faraday rotation of pulsars and extragalactic radio sources as well as data of physical and morphological properties of more than 500 radio galaxies of different morphological classes.
Variability study of the FBS M giants 0.2 MB
K. S. Gigoyan, G. R. Kostandyan
Abstract. We study in this paper variability of the late-type M giants found in the First Byurakan Survey (FBS) spectroscopic data base. We used phase dependent light – curves from large sky area variability data bases such as Catalina Sky Survey (CSS) and All-Sky Automated Survey for Supernovae (ASAS-SN). We used also the distance information derived from Gaia EDR3 to construct the Galactic distribution of the M – type giants from the second edition of the FBS Late-Type Stars catalogue including various kinds of long period variables.
Testing the evolution of the absolute magnitude of type Ia supernovae and cosmological parameters 0.5 MB
A. P. Mahtessian, G. S. Karapetian, M. A. Hovhannisyan, V. H. Movsisyan, and L. A. Mahtessian
Abstract. Computer simulations show that, in estimating cosmological parameters, the best agreement between theory and observation is achieved by assuming the evolution of the absolute magnitude of type Ia supernovae. This requires only 0.3m of evolution for the time corresponding to z = 1. This leads to zero density of hidden energy in the Universe.
No-z model: results and perspectives for accretion discs 0.8 MB
E. A. Mikhailov and M. V. Pashentsevay
Abstract. Accretion discs surround different compact astrophysical objects such as black holes, neutron stars and white dwarfs. Also they are situated in systems of variable stars and near the galaxy center. Magnetic fields play an important role in evolution and hydrodynamics of the accretion discs: for example, they can describe such processes as the transition of the angular momentum. There are different approaches to explain the magnetic fields, but most interesting of them are connected with dynamo generation. As for disc, it is quite useful to take no-$z$ approximation which has been developed for galactic discs to solve the dynamo equations. It takes into account that the disc is quite thin, and we can solve the equations only for two plane components of the field. Here we describe the time dependence of the magnetic field for different distances from the center of the disc. Also we compare the results with another approaches which take into account more complicated field structure.
Proper motion of the spectrally selected structures in Herbig-Haro flows 0.3 MB
T. A. Movsessian and T. Yu. Magakyan
Abstract. We present some results of the investigations of proper motions of spectrally separated structures in the Herbig-Haro (HH) outflows with the aid of Fabry-Perot scanning interferometry. This project was started more than twenty years ago on the 2.6m telescope of Byurakan Observatory and afterwards was continued on 6m telescope (Russia). We describe the progress of research in the frames of this project and focus in more detail on the results of the latest observations of HH 83 outflow system. The method of Fabry-Perot scanning interferometry allowed to reveal the morphology of high and low velocity structures not only inside the terminal working surfaces of the jets but also in their internal knots. As the great advance we consider the development of a methodology for measuring proper motions of already separated kinematical structures using observations in two epochs, which made it possible to reveal the physical nature of these structures. Concerning the HH 83 collimated outflow it should be noted that our first observations of HH 83 revealed two structures in its working surface with strongly different radial velocities, and the second epoch data allowed to measure their proper motions. The proper motions of these structures are nearly equal, which points that they are physically connected and represents forward and reverse shock regions in the terminal working surface of HH 83.
On the property of ”statistical identity” of solutions to some classical problems of the radiative transfer theory 0.2 MB
H. V. Pikichyan
Abstract. A probabilistic interpretation of the classical solution of the diffuse reflection problem (DRP) of radiation from a semi-infinite homogeneous scattering-absorbing medium on the language of random events in the simple case of monochromatic and isotropic scattering is constructed. A certain property of the so-called ”statistical identity” is specially defined. By using these two circumstances, it is possible to construct a simple symbolic scheme for the direct transformation of the solution mentioned above in the particular case of DRP into solutions to more general cases of DRP, which taking into account the anisotropy and incoherence of scattering, as well as the temporal dependence of the task on the act of absorption. Moreover, some generalization of the primary scheme makes it possible to directly obtain solutions of the DRP also for nonhomogeneous media and for general case of time dependence (on absorption acts and free flights between them) for the quanta diffusion process. At the same time, both the well-known results of the DRP decisions and some new ones were obtained.
An Integral Approach to the Theory of Classical Polytropes 0.3 MB
G. A. Saiyan
Abstract. A nonlinear Volterra integral equation of the second kind is used instead of conventional Lane-Emden differential equation to represent an alternative approach to finding exact solutions and analytical approximations to solutions of the Lane-Emden equation for classical polytropic models. This approach enables us to reproduce the well - known Lane- Emden (or, just Emden) functions for polytropic indices n=0,1,5 directly or by making use of the Laplace transform, and, being combined with some heuristic reasonings, derive analytical approximations to exact solutions for n = 1.5, 2 and ∞ in closed forms. The proximity of all suggested analytical approximations to the exact solutions are evaluated with the use of the mean square error estimator. Standard deviations are found to be of 10-3 by the order of magnitude. The approximating function of the isothermal density distribution enables us to calculate a theoretical rotation curve that reproduces main features of rotation curves of a set of spiral galaxies. Detailed mathematical calculations will be introduced in an extended paper which is under preparation.
On the STEM Concept Projection on the Field of Astronomical Knowledge 0.2 MB
L. A. Gheonjian
Abstract. Astronomy, as the result of activity and development of the technology of human cognition of his existence environment, should be considered as the basis for an effective educational approach. The STEM (Science, Technology, Engineering and Mathematics) approach has failed because of limitations caused by the focus on the needs of engineering education only. The STEM projection on the field of astronomical knowledge, technology of means, engineering of instrumentation and mathematical modeling as science and technology language, removes limitations and solves the task to form an educated person. This idea finds solid ground if from philosophy, as a tool for unification, we turn to psychology which studies systems organized around the phenomenon of memory with the goal to reflect and comprehend reality in order to create a new reality and environment for preservation of the viability of human being. This approach is present and developed in different aspects of The General Psychological Theory of Set of Dimitri Uznadze. Based on Uznadze, education is an organized process of accumulation in memory of information that we unconsciously, but adequately use in situations of reality recognizing them as already known. Consciousness serves the memory to create new sets of behavior in new previously unknown situations. Education seems to be ideal, if one step by step organizes situations-tasks of consciousness “switching on” to search for solutions in own memory, in external source or experimentally. If one uses the Psychology of Set as a model of the educational process, astronomy is the best information environment for it.
Preliminary Statistical Analysis of Lambda Bootis Stars 0.9 MB
S. Ghazaryan , G. Alecian, E. Paunzen, and A. A. Hakobyan
Abstract. To enlarge our database of Chemically Peculiar stars, we compiled published data concerning the Lambda Bootis stars observed by high-resolution spectroscopy techniques during last decades. In total, 62 Lambda Bootis stars have been added to the database. To deepen our knowledge on statistical overview of the abundance anomalies versus the physical parameters of stars, our data were compared with previous compilations, as well as with Gaia DR2 data. Different statistical tests were applied on our data for 20 chemical elements for the search of interesting correlations for different physical parameters in the atmospheres of those stars. We confirmed all previous results and obtained correlations between different physical parameters, but because of the lack of the data, we could not find new correlations. We hope, that Gaia EDR3 data, on which we are working now, will help us to improve our database and to understand the nature of all Chemically Peculiar stars.
Features of a Sample of Star-forming Galaxies in two Adjacent SBS Fields 0.6 MB
S. A. Hakopian
Abstract. Some results are presented on studies of a sample of about hundred galaxies (“100SBS”) from two adjacent fields of SBS (Second Byurakan Survey), which have spectral data in SDSS (Sloan Digital SkySurvey-www.sdss.org ).The work is carried out as a part of the long-term program (Hakopian, 2013) forin-depth study of the galaxies in seven selected SBS fields (including the two under investigation).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 SfG, i.e. star-forming galaxies. Obtained results showed good perspectives in using of our scheme for differentiation of activity phases of SfGs and for better statistics and comprehensive studies. Space distribution of 100SBS galaxies, what is important, homogeneously selected in continuous (32 sq.deg) area, was obtained using uniformly determined in SDSS redshift values. As it follows from the graphs plotted at 0.01 intervals the maximum of the distribution, with an equal number of Staforming and Starburst galaxies falls on the range 0.01<z<;0.019. The minimum of the distribution falls on the range 0.02<z<0.029 and more expressed for Starbursts. Also some difference is discerned in a diversity of morphological appearance of the galaxies composing two neighboring to it intervals.
Study of the X-ray properties of blazars, based on BZCAT catalogue 0.7 MB
G. M. Paronyan, A. M. Mickaelian, H. V. Abrahamyan, G. A. Mikayelyan, and A. G. Sukiasyan
Abstract. The analysis of blazars’ parameters from BZCAT leads to a conclusion that they do not have the same properties. The preliminary criterion to include an object in the catalog was the strong radio emission; however, two type of radio sources were selected: BL Lacertae (BLL) objects and Flat Spectrum Radio Quasars (FSRQ). As a number of properties are typical of blazars (strong radio emission, optical variability, continuum optical spectra, polarization, high luminosity, etc.), using the X-ray data, we investigate them to clarify which property plays the most significant role in their classification as blazars. In addition, 48% of blazars have detected radiation in X-ray have detected. We give the average statistical characteristics of blazars based on our analysis and calculation
PhD THESES RELATED ARTICLES
Study of DFBS Late-Type Stars at High Galactic Latitudes 0.3 MB
G. R. Kostandyan
Abstract. We study in this thesis relatively bright late-type giants found in the First Byurakan Survey (FBS) data base. We present the 2nd version of the catalogue of FBS LTS with new data (FBS LTS v2), 1471 objects. It is a homogeneous and complete database for high- Galactic late-type stars, including M and C types. Since 2007, all FBS low-resolution spectral plates are digitized. All DFBS spectral plates are analyzed with FITSView and SAO Image ds9 and numerous relatively faint LTS were discovered. We have made cross-correlation with DFBS, USNO-B1.0, 2MASS, AllWISE, IRAS PSC/FSC, AKARI, ROSAT BSC/FSC, GCVS, SDSS and added updated SIMBAD data. For numerous new detected objects, we present accurate DSS2 positions, approximate spectral subtypes refined from the DFBS low-dispersion spectra, luminosity classes estimated from 2MASS colours, and available proper motions for 1471 FBS LTS. The Revised and Updated Catalogue v2 lists a large number of completely new objects, which promise to extend very significantly the census of M giants, faint N-type AGB carbon stars, CH-type carbon giants at high Galactic latitudes, also M dwarfs in the Solar vicinity up to 16.0m-17.0m in visual. Phase dependent light-curves from large sky area variability data bases such as Catalina Sky Survey (CSS) and All-Sky Automated Survey for Supernovae (ASAS-SN), and the early installment of the third Gaia data release (Gaia EDR3) photometric and astrometric data have been used to characterize our sample of 1100 M-type giants found and 130 C-type stars at high latitudes. We show the behaviour of our sample stars in a Gaia DR2 color–absolute magnitude diagram (CaMD), the Gaia-2MASS-diagram, including two alternative versions, and the logP-K-diagram. In this way we explore the potential of these diagrams and their combination for the analysis and interpretation of datasets of LPVs. We show the possibility to classify stars into M- and C-types and to identify the mass of the bulk of the sample stars.