Abstracts
Oral Presentations Poster Presentations
Oral Presentations
A stochastic sampling method for the analysis of eclipsed pulsations
András Bókon, Observatory of Baja of University of Szeged
andras.bokon@gmail.com
Observation of stellar oscillations has a history of hundreds of years. Their importance lies in their information content about the internal stellar structure. Recent space missions have hugely extended our knowledge about them. However, in order to go beyond general characterization of stellar interiors and perform asteroseismic inversions, the identification of many modes is still required. In this respect pulsating stars in eclipsing binaries offer a unique opportunity, if the effective surface sampling of the eclipse events can be properly analysed. In my talk I present an investigation of new possibilities to perform mode identification in such systems, using parameter fitting driven by stochastic methods.
Spectral classification of ultracool dwarf candidates with OSIRIS/GTC. First detection of Balmer line emission from the dwarf carbon star LSR J2105+2514.
Antoaneta Antonova, Peter Pessev, Valeri Golev, Dinko Dimitrov Institute Of Astronomy with NAO, BAS
tantonova@astro.bas.bg
Based on low-resolution OSIRIS/GTC optical spectra, we have assigned spectral classes of 45 poorly studied ultracool dwarf candidates from the 2MASS database. For almost all of the targets this is the first optical spectral classification. For the dwarfs, showing Ha emission, we have calculated the ratio of H alpha to bolometric luminosity, which is the most common characteristic of magnetic activity in cool stars. We also include distances from GAIA. For one of our targets – LSR J2105+2514, classified as dwarf carbon star by Lowrance et al. (2003 ApJ, 584, 95), we confirm this classification and report Hα and Hβ line emission in the spectrum for a first time. Dwarf carbon stars (dC) are low-mass main sequence stars that have undergone mass-transfer binary evolution. The Balmer line emission from these objects can be due to coronal activity of the main sequence dwarf. The activity itself may be due to either magnetic activity of the star, or it can be caused by spin-up from accretion or tidal locking.
Variables in the field of M31 stellar complex OB81
Antoniya Valcheva, Sofia university "St. Kliment Ohridski"
valcheva@phys.uni-sofia.bg
As a result of the photometric analysis of stars in fields, centered on the stellar complex OB 81 in M31, observed in 2018 with the 50/70 cm Schmidt telescope and archival data from 2000, obtained with a 2m telescope at NAO Rozhen, ~50 candidates for variable stars were found, 6 of which were identified with known Cepheids, 1 – with a known eclipsing binary from the GCVS (Artyukhina et al., 1995) and 1 – with a variable WISE object (Cutri et al., 2013). In order to search for unknown variable candidates, we added new data obtained in 2018 with the 2m telescope at NAO Rozhen. With the supplement of PTF (http://www.ptf.caltech.edu) data for 2010-2015, the light curves have been constructed and the periods of the brightest known and candidate variable in the field of OB81 have been determined.
Byurakan Astrophysical Observatory: present and future activities
Areg M. Mickaelian, Byurakan Astrophysical Observatory (BAO)
aregmick@yahoo.com
I will give a review of current and future activities at V. Ambartsumian Byurakan Astrophysical Observatory (BAO) of the National Academy of Sciences of the Republic of Armenia (NAS RA). It was founded in 1946 and for many years it is one of the most important astronomical centres of the Middle East. Its main observing facilities are the 2.6m classical reflector and 1m Schmidt telescope. BAO is recognized by the Armenian Government as a National Value. It is one of the IAU regional centres; it hosts the IAU South West and Central Asian Regional Office of Astronomy for Development (SWCA ROAD). We have the Armenian Virtual Observatory (ArVO) project and we are part of the International Virtual Observatory Alliance (IVOA). Our best observational material, Markarian Survey (or the First Byurakan Survey, FBS) and its Digitized version, the DFBS, is included in UNESCO International Register of documentary heritage “Memory of the World”. At present BAO has 41 researchers and 104 employees in total. There are 10 research departments, including BAO traditional subjects and new subjects, such as Astrochemistry, Astrobiology and Exoplanets, High-Energy Astrophysics, and Compact Cosmic Bodies and Relativistic Gravity. BAO is rather active in organizing international meetings and schools. Here 6 IAU symposia and colloquia have been organized (1966, 1986, 1989, 1998, 2001 and 2013). The European Annual Astronomical Meeting JENAM-2007 was also organized in Armenia. We have founded the series of Byurakan International Summer Schools (BISS) and 6 such schools have already been held (2006, 2008, 2010, 2012, 2016 and 2018), one of which was combined with the IAU International School for Young Astronomers (ISYA-2010). We publish two journals, Astrofizika/Astrophysics and Communications of BAO. In the forthcoming years, we plan to expanding our activities in the direction of more subjects, such as Space Sciences and Technologies, running more telescopes, including robotic ones (50-60 cm size), and enlarging the research staff. Areg M. Mickaelian
The solar cycles influence traces in Pinopsida-trees annual rings time series
Boris Petrov Komitov, BAS - Institute of Astronomy and NAO
komitovboris97@astro.bas.bg
The indirect space climate influence over Pinopsida-trees growth in South Bulgaria during 19-20 centuries is the subject of this presentation. The study is based on analysis of annual tree ring widths data for four long lived tree samples.
Using The Properties of Kinematically Distinct Components as Fossil Records for Galaxy Formation and Evolution
B. Nedelchev, L. Coccato, E. M. Corsini, M. Sarzi, T. de Zeeuw, A. Pizzella, E. Dalla Bontà, E. Iodice, L. Morelli
University of Hertfordshire
b.nedelchev@herts.ac.uk
The Kinematically Distinct Components (KDCs), present in a non-neglicable fraction of local galaxies, are viable testbeds to study the processes of galaxy formation and evolution. In particular we would focus on a small number of those galaxies with KDCs harboring counter-rotating cores. Through a kinematic decomposition technique we have separated the individual contributions to the spectra of the two kinematically distinct components in the largest to date sample of galaxies with present stellar counter rotation, drawn from the integral-field unit (IFU) Mapping Nearby Galaxies at APO (MaNGA) survey, and two particular galaxies NGC 448 and NGC 4365, observed with the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope. Based on this decomposition we have extracted the ages, metallicities, and alpha-enhancement of the underlying stellar populations of both components at each spatial position in the field of view. Combined with the extracted kinematics such an analysis allows us to find whether these counter-rotating KDCs are either truly decoupled separate embedded components (e.g. a disk in the case of NGC 448) or, like the case of NGC 4365, are simply a projection ffect stemming from the complex orbital structures present in massive elliptical galaxies with intrinsically triaxial gravitational potentials.
Big Cosmological Influence of Tiny Lepton Asymmetry During BBN
Daniela Kirilova, IA NAO, BAS
dani@astro.bas.bg
Contrary to the baryon asymmetry of the universe, which has been measured with high precision, lepton asymmetry of the universe L has not been measured. We explore the cosmological effects of tiny lepton asymmetry |L|<<0.001 during the epoch of Big Bang Nucleosynthesis, which may provide information for this elusive characteristic of the universe. We discuss both the case of L generated in active-sterile neutrino oscillations and the case of relic L, present in the primeval plasma before neutrino oscillations start. Tiny oscillations generated L always suppresses neutrino oscillations at small mixing, and correspondingly, reduces the overproduction of He-4 due to neutrino oscillations. On the other hand, depending on the oscillation parameters value, tiny relic L may enhance or suppress active-sterile neutrino oscillations, and, hence, increase or decrease He-4 overproduction caused by neutrino oscillation. We update the empirical relations between oscillations parameters and lepton asymmetry value corresponding to the qualitatively different types of lepton asymmetry effect. Relic L, which inhibit neutrino oscillations, can alleviate BBN constraints on oscillation parameters. We show that, eventual observations of neutrino active-sterile oscillations with parameters not allowed by BBN, present a lower limit for the value of the lepton asymmetry of the universe.
Astronomical problems for school olympiads based of moments of astronomy history
Eva Bojurova, Astronomical observatory and planetarium N. Copernicus - Varna, Bulgaria
eva.bojurova@gmail.com
Presented are a number of problems created for the National Astronomy Olympad in Bulgaria and based on intriguing moments from the history of astronomy. To solve the problems, the students should, in a simplified way, reproduce the reflections of some notable astronomers which have led them to a certain insight or discovery. The role of such problems in attracting students' interest and provoking their thinking is considered.
The National Astronomical Observatory Rozhen - current status and plans for upgrade
Evgeni Semkov, IA and NAO, BAS
esemkov@astro.bas.bg
NAO Rozhen is the biggest one-time Bulgarian investment in scientific infrastructure and a leading astronomical center in the South-East Europe. The 2-m RCC telescope of Rozhen Observatory is equipped with four new professional CCD cameras (two ANDOR iKon-L BEX2-DD cameras, ANDOR iKon-L E2V 42-40 and ANDOR Newton 940), coudé and éshelle spectrographs, a two-channel focal reducer, broad band and interference set of filters. NAO Rozhen has two small telescopes for optical observations: the 50/70 cm Schmidt telescope and 60 cm Cassegrain telescope. Both telescopes are equipped at present with CCD cameras with thermo-electric cooling: FLI PL 9000 at the Cassegrain telescope and FLI PL 16803 at the Schmidt telescope. The 15 cm Lyot-coronagraph in observatory is designed for solar observations. NAO Rozhen is at the heart of the RACIO Consortium, the unification of the three major professional astronomical organizations in Bulgaria. On 21.09.2010 the Bulgarian Government included RACIO in the National Roadmap of Research Infrastructure (Resolution 692/21.09.2010 by the Council of Ministers). In 2018 the target funding of the National Roadmap was launched and we started upgrading the equipment in the Observatory. Our plans include the installation of a new robotic telescope (1.5-1.2 meters), the construction of a faint objects spectrograph, renovation of the solar telescope, buying new CCD cameras, improvement of the working conditions in the Observatory.
The diversity of the chemical composition of the Martian Trojan asteroids
G. Borisov, A. Christou, S. Bagnulo, A. Cellino and A. Dell’Oro
Armagh Observatory, UK
Galin.Borisov@Armagh.ac.uk
The so-called Martian Trojans are asteroids orbiting in the stability regions corresponding to the L4 and L5 Lagrangian points of Mars. Their existence is thought to date back to the early epochs of the history of the solar system. Among the ten confirmed Martian Trojans (as of June 2018), nine belong to L5 and only one belongs to L4. The goal of this investigation is to determine the origin and surface composition of the Martian trojan asteroids. We have obtained visible and/or near-infrared reflectance spectra of the asteroids using X-SHOOTER mounted on VLT at ESO, ACAM on WHT and FoReRo2 on 2mRCC Telescope at Rozhen Observatory. The spectroscopic results were compared with the spectra of a number of taxonomic classes and subclasses and different measurements form the RELAB database of NASA. We found that the asteroids from the so-called Eureka family belong to the olivine-dominated A, or Sa, taxonomic class. As Eureka itself is also an olivine-dominated asteroid, it is likely that all family asteroids share a common origin and composition. The other non-family members have a different composition, which points out that they must have a different origin. One of them, (121514) 1999 UJ7, is a primitive object with a very slow spin rate, almost 2 days. Its inferred composition can be consistent with a volatile-rich object originally accreted beyond the snow line of the solar system and subsequently evolved to reach the inner regions of the solar system. The other non-family member, (101429) 1998 VF31, has a spectrum similar to spectra of lunar crater features from the highlands, which point out a completely different origin than the rest of the Martian trojan asteroids.
UU Cas-massive Close binary with accretion disk
Gojko R. Đurašević
Astronomical observatory Belgrade
gdjurasevic@aob.rs
In this presentation we show the results of the study of the UU Cas based on the spectroscopic and photometric observations data. We derived the mass-ratio of the components q=0.505 and clearly show that the spectral features and light curves of the system can be successfully interpreted by the CB Roche model in which the less-massive donor fills the critical Roche lobe and transferring mass on the more massive gainer, which is mostly hidden with a large optically and geometrically thick accretion disk. Orbital and physical parameters of the components and accretion disk characteristic are estimated, as well as the evolutionary progenitor model.
Gaia DR2 and Serbian-Bulgarian investigations
Goran Damljanovic
Astronomical Observatory, Belgrade, Serbia
gdamljanovic@aob.rs
On April 25th 2018, the second release of the Gaia catalogue (DR2) was appeared, and it is based on 640 days of Gaia satellite observations (1.75 yr or 21 months). The period is August 22nd 2014 - May 23rd 2016 (with some interruptions). The reference epoch is J2015.5, and the positions and proper motions refer to the ICRF. The DR2 is publicly available in the online Gaia Archive (https://archives.esac.esa.int/gaia). After Hipparcos, the GAIA (Global Astrometric Interferometer for Astrophysics) is the cornerstone mission of European Space Agency (ESA), and the next solution (DR3) is planed for the first half of 2021. The main results of DR2 with some Serbian-Bulgarian investigations about it are presented, here.
The puzzling Algol-type star with oscillating component GSC 3889-0202
Ivanka Stateva, M. Napetova, D. Dimitrov, I. Kh. Iliev
Institute of Astronomy and NAO, BAS
stateva@astro.bas.bg
We present here results from photometric and spectroscopic study of the eclipsing binary star GSC 3889-0202. The observations have been made in two epochs - 2008 and 2016. The CCD BVR photometry was carried out with the 60cm Cassegrain and the 50/70cm Schmidt telescopes of BNAO-Rozhen. The collections of spectra consists Coudé-spectra obtained with the Coudé-spectrograph and echelle-spectra obtained with the ESPERO echelle spectrograph of the 2m RCC telescope of BNAO- Rozhen. We discuss the differences in light curves and radial velocities determined in two different epochs and the reasons for such discrepancies.
Spectral observations of High-mass X-ray binaries
K. A. Stoyanov & R. K. Zamanov
Institute of Astronomy and National Astronomical Observatory, BAS
kstoyanov@astro.bas.bg
We present high-resolution spectral observations of selected high-mass X-ray and γ-ray binaries (LSI + 61 303, MWC 656, MWC 148, X Per) obtained with the ESPERO spectrograph at the Rozhen NAO. They are binary systems consisting of a rapidly rotating B star and a compact companion - neutron star or black hole. We measure parameters of the emission lines and estimate the sizes of the circumstellar discs using these emission lines. We study the disc truncation and the interaction between the compact objects and the circumstellar disc of the Be star. This research is supported by the grant КП-06-Н28/2 08.12.2018 by Bulgarian NSF.
On the extraction of power-law tails of the probability density functions in star-forming clouds
L. Marinkova
Sofia University "St. Kliment Ohridski", Faculty of Physics
ln@phys.uni-sofia.bg
The probability density function (pdf) of column density (N -pdf) is an important indicator for understanding the physics and evolution of star-forming regions. The typical N -pdfs could be decomposed to a lognormal part and a power-law tail (PLT) at their high-density ends. A new approach, called “adapted bPlfit method”, presented by Veltchev et al. 2019, assesses the power-law part of an arbitrary distribution, without any assumptions about the other part of this distribution. Applying this method to data from current numerical simulations on galactic scale (SILCC), we can study how the PLT parameters are affected by the choice of the frame, used to define evolving giant molecular clouds in high resolution regions. The comparison between the obtained PLT parameters when applying the adapted bPlfit method and those of its analogue Plfit, which uses unbinned data, shows the reliability of the adapted bPlfit method when working with large arrays of observational and numerical data.
A study of the hierarchical structure of MC Rosette based on observational and numerical data.
Mariyana Bogdanova
Sofia University, Faculty of Physics
mpetrova@phys.uni-sofia.bg
The local structures in molecular clouds, often described as filaments and clumps, are hierarchical and self-similar structures over a wide range of scales and occur in conditions of compressible supersonic turbulence and gravity. The parameters are highly dependent on the selected clumps selection approach – if the clumps are considered as a set of independent objects or as an hierarchy of embedded structures. We study the hierarchical structure of the MC Rosette via applying the Dendrogram method on line maps in two observational tracers,12CO, 13CO (FCRAO) and dust emissions map (Herschel). The analysis of the scaling lows “velocity dispersion – size” and “mass – size” reveals if they are an artefact of the method itself or represent the actual hierarchical structure of MC, and the virial analysis of the clumps reveals their gravitational connectivity. The resulted “mass - size” relation on different scales is an indication for the multifractal structure of the clouds through their fractal dimension.
Why is the proclaimed amount of dark matter overestimated?
Michal Krizek
Institute of Mathematics, Czech Academy of Sciences, Zitna 25, 115 67 Praha 1, Czech Republic
krizek@cesnet.cz
According to the standard cosmological model, our universe contains more dark matter than ordinary baryonic matter and the ratio of masses of dark matter to baryonic matter is about 6:1. We present 10 counterarguments showing that such a claimed amount of dark matter can be a result of vast overestimation and does not conform to reality. Some of these counterarguments can be convincingly verified even by simple hand calculations. The cosmological parameters corresponding to the present time were determined by the three seemingly independent methods of Baryonic Acoustic Oscillations, Cosmic Microwave Background Radiation, and Supernovae type Ia explosions. Nevertheless, these methods are not independent, since they are all based on the same Friedmann equation. This equation is a direct mathematical consequence of Einstein's equations that were applied to a homogeneous and isotropic universe. Furthermore, to extrapolate Einstein's equations from the Solar system to the whole universe, which is at least 15 orders of magnitude larger, is questionable. In truth, it is more likely that the measured data just indicate that the extrapolation is wrong, since it requires one to introduce some exotic dark matter and dark energy.
Optical counterpart of gamma-ray observations of AGNs
Milen Minev, Evgeni Ovcharov, Vladimir Bozhilov
Sofia University "St. Kliment Ohridski"
msminev13@gmail.com
We present and discuss original results of а photometric study of different type AGNs 2-meter RCC and 50/70cm Schmidt telescopes of the National Astronomical Observatory (NAO) – Rozhen, and 35cm Newton telescope of Student Astronomical Observatory (SAO) - Plana. We demonstrate an observed change of the optical flux as a counterpart of flux changes in high energy gamma-rays observed with 17m MAGIC telescopes.
Quasiperiodicity of some of the quasars important to ICRF-Gaia CRF link
Miljana D. Jovanović and Goran Damljanović
Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia
miljana@aob.rs
The ESA/Gaia astrometric mission will provide a catalogue of about billion stars and 600 000 quasars (QSOs). Some of QSOs could be the basis of a new optical reference frame. To link the ICRF (based on the VLBI observations of quasars at radio wavelengths) with the future Gaia CRF (at optical wavelength) it is required to observe a set of QSOs which are visible at optical wavelengths (brighter than G=20 mag). Only about 70 sources of the ICRF are suitable for this link, and because of that this number has increased by 47 sources with high astrometric quality. Our observations of 47 candidate sources have been carried out by using three telescopes: two of them are located at the Astronomical Station Vidojevica (of the Astronomical Observatory of Belgrade) and the third one at the Rozhen Observatory of NAO BAS (Bulgaria). The brightness variability was analysed by F-test, and the periods of quasivariability were estimated with method of Least Squares. The results of the mentioned analysis concerning several objects and their comparison stars (for period mid-2016 until now) are presented here.
Low luminosity late O stars in the VFTS. Classification and main physical properties
Nevena Markova
IANAO, Bulgaria
nmarkova@astro.bas.bg
Bright, massive stars play an important role in the evolution of galaxies and of the Universe as a whole. The Tarantula nebula (30 Doradus) in the Large Magelanic Cloud comprises the most massive starburst cluster and giant H~II region in the Local Group, and it contains the most massive stars so far known. Thus, it is appropriate that 30 Dor is the subject of the unprecedented spectro-scopic dataset, obtained by the VLT-FLAMES Tarantula Survey, which contains high-resolution observations of about 800 OB stars in this field. During the survey, a large number of low luminosity late O-giants and bright giants with too high surface equatorial gravities and a peculiarly low helium content were discovered. A possible explanation for this puzzling discrepancy is presented in this talk.
Hot wind in the symbiotic binary AG Peg during its 2015 outburst
N. Tomov, M. Tomova, R. Zamanov
IA and NAO
tomov@astro.bas.bg
Based on high resolution data taken with the 2m telescope of Bulgarian National Astronomical Observatory we investigated some optical lines in the spectrum of the symbiotic binary AG Peg during its 2015 outburst and in the period of quiescence preceding this outburst. The profile analysis gives possibility to conclude about the evolution of the structure of the outbursting compact object, which, from its side, sheds some light on the possible reason for the outburst.
Astronomical alignments and calendars of the peak sanctuary Kokino
Olgica Kuzmanovska
Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University, Skopje, Republic of North Macedonia
olgicak@pmf.ukim.mk
The locality “Taticev Kamen”, located near village Kokino in the northeast part of Republic of North Macedonia was important religious site during the Bronze Age, with cult practice connected with the periodic motion of prominent celestial objects. We present the simple calendars related with the astronomical alignments that mark the rising sun and moon positions on particular dates and the heliacal rising of some stars for purpose of following the vegetation cycles and arranging agricultural activities.
Comparative analysis of clump populations in Rosette MC extracted by the methods GAUSSCLUMPS and DENDROGRAMS
Orlin Stanchev
Department of Astronomy, University of Sofia, Faculty of Physics
o_stanchev@phys.uni-sofia.bg
The recent high-resolution observational studies of molecular clouds in the Galaxy reveal an extremely complex, clumpy and filamentary structure. Dust opacity data and molecular line maps of different tracers of the gas observed in variety of star forming regions often manifest the hierarchical and fractal nature of these local structures. The detected large non-thermal linewidths which scale with the size of the cloud have been interpreted as indicators of the presence of supersonic turbulence. Together with the gravity these are the primary physical agents regulating the formation of dense local features in the clouds with properties predetermining the fundamental processes of star formation. These physical properties strongly depend on the adopted clump extraction approach - whether we examine the clumps as an ensemble of independent objects or rather we look at them as a hierarchically connected embedded structures. We show a comparative analysis of the derived properties of the obtained clump populations using two different extraction techniques: hierarchical (DENDROGRAM) and non hierarchical (GAUSSCLUMPS). The chosen star forming region is Rosette molecular cloud, using observational data for three indicators: 12CO and 13CO line emission maps (FCRAO) and dust emission map (Herschel).
Importance of Lyman limit systems between z=1 and z=2
Sándor Papp, Gerard Williger
University of Szeged
pappsandor@titan.physx.u-szeged.hu
Lyman limit systems (LLSs) are in connection with the circumgalactic matter (CGM). LLSs in the line of sight of background quasars results absorption lines in the quasar spectra and a break at the HI Lyman series limit (rest wavelength 912 A). HI absorption lines represents the CGM or intergalactic matter (IGM) that can fall into the galaxy, MgII and other lowly ionised metal lines refers galaxy halos and outflows, making LLSs the tracers of galaxy evolution. Measurements shows that at z<1 the metallicity distribution function is bimodal, while at z>2 it shows low metallicity. Using GALEX spectra to examine these absorbers between redshifts z=1 and z=2 we plan to figure out how metallicity occurs in this interval.
Magnetism in Cool Evolved Stars: the Single M-Giants EK Bootis and β Pegasi
S. Georgiev, R. Konstantinova-Antova, A. Lèbre, M. Aurière, C. Charbonnel, A. Palacios, R. Bogdanovski
IA with NAO, BAS
sgeorgiev@astro.bas.bg
We present our long-term spectropolarimetric study of the single active M giants EK Bootis (M5III) and β Pegasi (M2.5II-III). For each star, the variability of the surface-averaged longitudinal component of the magnetic field (Bl), along with the behaviour of different spectral activity indicators is shown. We compare the observed variations in the two giants and discuss possible physical explanations for their magnetic activity.
Correlations between chromospheric activity and physical parameters of contact binary stars
Tibor Mitnyan
University of Szeged
mtibor@titan.physx.u-szeged.hu
There are lots of contact binaries that show activity signals, and stellar activity can alter the formation and evolution of these systems. One of these signals is the emission excess observed in several ultraviolet and optical absorption spectral lines (Ca II H+K, Mg II, Hα), which indicates ongoing chromospheric activity. As different systems have different physical and orbital parameters, the strength of chromospheric activity can also be different, hence, it seems to be evident that there is a relation between these quantities. In previous studies on contact binaries, this topic has been investigated only in the ultraviolet domain involving the Mg II line; they show that there is a correlation between the strength of the chromospheric activity and of several quantities e.g. orbital period, B-V colour index, or the logarithm of the inverse Rossby-number. There are no comprehensive studies in the literature based on the analysis of the optical Hα-line, however, the equivalent width of this spectral line can be also used to measure the strength of the chromospheric activity. Therefore, our main objective is to find possible correlations between the strength of the chromospheric activity on contact binary stars and all of their physical and orbital parameters that can be derived from our observations. In order to make a decent statistical analysis, as many targets have to be observed as possible. For this purpose, we regularly obtain spectra with the 1m telescope located at Piszkés-tető Mountain Station, Hungary. For fainter targets, we occasionally observe with the 2m telescope of Rozhen Observatory in Bulgaria. To increase the number of the derived quantities and construct a detailed physical model of the observed targets, we also try to obtain simultaneous photometric measurements with the 0.5m telescope at the Baja Astronomical Observatory, Hungary. This also allow us to study the more interesting or peculiar systems in more details, for example getting a deeper insight in short-scale variations of the photospheric and chromospheric activity (within one night), as can be seen in our recent paper, Mitnyan et al. 2018 (A&A, 612, A91).
Formation of Impact Craters; some ideas
Vladan Celebonovic
Inst.of Physics, Univ. of Belgrade, Serbia
vladan@ipb.ac.rs
Surfaces of the Earth, Moon, some planets and asteroids are filled with craters. A part of these is of volcanic origin, and they are outside the scope of this presentation. However, a part is due to impacts of various smaller objects into their surfaces. This paper will attempt to give an introduction to the following problem “ Knowing all the measurable parameters of the crater (which is possible in the case of the Earth) and if (luckily) a piece of the impactor is found, what can be concluded about the impactor?” It turns out that by using standard condensed matter physics and the law of conservation of energy it is possible to derive an equation which links parameters of the impactor with parameters of the material of the target. This expression was applied to several known examples, and the results are encouraging. This problem offers possibilities for collaboration between physicists and astronomers. They will be briefly discussed.
Photopolarimetrical Study of Blazar-type AGN OJ287 with the 2m RCC Telescope at NAO Rozhen
Vladimir Bozhilov, Evgeni Ovcharov, Milen Minev
Dept. of Astronomy, Faculty of Physics, Sofia University, Bulgaria
vbozhilov@phys.uni-sofia.bg
We present and discuss original results of а photopolarimetric study of the blazar-type AGN OJ287 using the Focal Reductor FoReRo-2 of the 2-meter RCC telescope of the National Astronomical Observatory (NAO) – Rozhen. We demonstrate an observed change of the position angle (P.A.) that is in good agreement with previous measurements. We discuss this as an indication of a correlation between the change of brightness in R-band and the change in the degree of polarization. The authors would like to acknowledge support for this work by National Science Programme "Young Scientists and Postdoctoral Students 2019", Bulgarian National Science Fund under grant DN18-10/2017 and National RI Roadmap Projects DO1-157/28.08.2018 and DO1-153/28.08.2018 of the Ministry of Education and Science of the Republic of Bulgaria.
Spectropolarimetric observation of Be/X-ray binaries X Per and MWC 656
Yanko Nikolov
Institute of Astronomy and National Astronomical Observatory
ynikolov@astro.bas.bg
The Be/X-ray binaries consist of compact object (black hole or neutron star) orbiting a Be-star. They are “close” binary systems and transfer of mass from the optical component to the compact object occurs. When unpolarized light undergoes scattering (Thompson scattering) in the circumstellar disc around the Be-star, the scattered light is linearly polarized. The degree of polarization depends on the orientation of the disc relative to the line of sight. We present spectropolarimetric observation of X Per and MWC 656, obtained with the 2-Channel Focal Reducer (FoReRo2), attached at the Cassegrian focus of the 2.0m RCC telescope of the Bulgarian National Astronomical Observatory Rozhen
Supernova analysis with MCMC method.
Zoltán Jäger
Baja Observatory of University of Szeged, Hungary
jagerz24@gmail.com
Supernovae are extremely energetic explosions, which highlight the violent deaths of various types of stars. Studying such cosmic explosions may be important because of several reasons. Supernovae play a key role in cosmic nucleosynthesis processes, and they are also the anchors of methods of measuring extragalactic distances. Several exotic physical processes take place in the exploding ejecta produced by the explosion. In my work I modeled the brightness as a function of time (i.e. the light curve) with numerical codes developed by myself and others. The code uses Marcow Chain Monte Carlo (MCMC) algorithm to search and determine the most important basic physical parameters of the supernova, i.e. the radius of the progenitor star, the mass of the ejected envelope, the mass of the radioactive nickel synthesized during the explosion, etc without supervision from the user.
Poster Presentations
The light curve analysis of the blazar 3C 454.3
B. Mihov, L. Slavcheva-Mihova
Institute of Astronomy and NAO, Bulgarian Academy of Sciences
bmihov@astro.bas.bg
The blazar class of active galactic nuclei involves BL Lac objects and flat-spectrum radio-quasars. 3C 454.3 is among the brightest representatives of the latter type, in particular, a highly polarized quasar. We report the results of the archival photometry of 3C 454.3 obtained in the course of various monitoring programmes and surveys. We do a detailed characterization of the light curves. The source shows variability with an amplitude of about 1 mag. Structure function analysis is performed and discussed in the framework of the blazar models.
Disc’s parameters and the accretion efficiency of two interacting binary stars
Daniela Boneva
Space Research and Technology Institute, BAS
danvasan@space.bas.bg
We investigate the disc's configuration around the primary star after the mass transfer being started, in two binary stars with compact objects. The interacting processes between the close components have an main effect on the established formation. Using online data of the accreting flow parameters, the disc’s structure models are suggested. In the result, the dependences of both a disc’s model and parameters against variations in the radius, and the model flux against wavelength are presented. We estimate the disc-accretion efficiency on the base of the obtained parameters. A possible relation to the level of the objects activity is presumed. We apply the observational data and variations in brightness of the two binary stars are detected.
Light curve of 15691 Maslov asteroid
E. Vchkova-Bebekovska, S. Boeva, G. Apostolovska, G. Latev, B. Petrov
IA and NAO, BAS
sboeva@astro.bas.bg
Photometric observations of asteroid 15691 Maslov, with duration of 8 hours, were performed with 2 m and 50/70 cm Schmidt telescope at NAO Rozhen. The light curve showed amplitude of 0.3 magnitudes and probably its rotation period was about 7 hours. The color indices of the asteroid indicate that 15691 Maslov belongs to the S spectral type.
Morphology of some quasars suitable for the link between ICRF and future Gaia CRF
G. Marković, G. Damljanović
Faculty of Mathematics, University in Belgrade
gbesic@yahoo.com
This poster presents our first results of studying morphology of some quasars suitable for the link between ICRF and future Gaia Celestial Reference Frame. Results are obtained using Galfit software and observations of quasars from 1.4m telescope at Astronomical Station Vidojevica in Serbia. It is necessary to study photometry and morphology of "link objects" because of axes stability of the future Gaia CRF.
Star Formation in Mrk 477
L. Slavcheva-Mihova, B. Mihov
Institute of Astronomy and NAO, Bulgarian Academy of Sciences
lslavcheva@nao-rozhen.org
Mrk 477 is considered the closest obscured quasar, a type II ultra luminous Infrared galaxy (ULIRG). This class of objects could be linked to QSOs by the evolutionary sequence, originally proposed by Sanders (1988). According to it a major merger of gas-rich galaxies triggers both intense star formation and quasar activity and the resulting system is classified as a ULIRG. We build the IR-to-UV spectral energy distribution (SED) of Mrk 477; a circum-nuclear region (CNR) SED is also constructed involving high-resolution data. The SEDs are fitted with the AGNfitter code accounting for the emission accretion disk, torus, host galaxy stellar population, and cold dust related to the star formation (SF) regions. Structure and colour maps are also created. Thus, we estimate the SF parameters (history, age, rate, etc.) of Mrk 477 accounting for the active nucleus, less pronounced in the case of type II objects. The results prompt a powerful SF in the CNRs. The relation between the SF and active galactic nucleus (AGN) parameters is studied. Based on high-resolution data, we search for signatures of AGN feedback on star formation.
Bulgarian - Serbian collaboration:Advantages of the simultaneous observations
S. Boeva, G. Latev, B. Spassov, Y. Nikolov, P. Nikolov, R. Zamanov, Z. Cvetcovic, G. Damljanovic, R. Pavlovic, O. Vince, M. Sekulic
Institute of Astronomy and National Astronomical Observatory, BAS
glatev@astro.bas.bg
We present an example of simultaneous photometric and spectral observations obtained at NAO Rozhen, ASV Vidojevica and AO Belogradchik - on 27.07.2016 we observed the symbiotic variable RS Oph in UBVRI bands and tried to obtain low dispersion spectra. We analyzed the overlapped parts of the light curves to check for photometric shifts between individualmagnitudes of each telescope.
CCD parameters evaluation using photon transfer analysis technique
Georgi Latev & Valery Genkov
Institute of Astronomy and National Astronomical Observatory, BAS
glatev@astro.bas.bg
We performеd laboratory measurements of selected CCD cameras using a standard designed light box. The photon transfer analysis technique was applied in order to evaluate camera's system parameters like a conversion factor (KDC gain), readout noise, Photo-response Non-Uniformity (PRNU), Full-well capacity, dynamic range, and signal limit value between shot and fixed pattern noise regimes. The results are summarised and briefly discussed.
Black body temperature vs. color indices: A grid constructed by data from Filter Profile Service at Spanish Virtual Observatory (SVO)
Georgi Latev & Radoslav Zamanov
Institute of Astronomy and National Astronomical Observatory, BAS
glatev@astro.bas.bg
We present a tabulated grid of values of color indices (U-B), (B-V), (V-R), and (V-I) and Black body temperatures. The data can be used for initial temperature evaluation of the target objects (undergo black body emission conditions) using the color indices calculated by photometric measurements. The zero points and the effective wavelengths used are from Filter Profile Service at Spanish Virtual Observatory ( SVO).
Comparison of photometric results between the Serbian and Bulgarian telescopes and activities in line with Gaia Alerts (Gaia-FUN-TO)
G.Damljanovic, S.Boeva, G.Latev, R.Bachev, O.Vince, M.D.Jovanovic, Z.Cvetkovic and R.Pavlovic
Astronomical Observatory, Belgrade, Serbia
gdamljanovic@aob.rs
We established the local cooperation "Serbian-Bulgarian mini-network telescopes" at 2013, and two SANU-BAN joint research projects: "Observations of ICRF radio-sources visible in optical domain" (during 2014-2016), and "Study of ICRF radio-sources and fast variable astronomical objects" (for the period 2017-2019); the head is G.Damljanovic. Here, some main results of that cooperation are presented, as comparison of Serbian and Bulgarian telescopes/CCD cameras/filters via photometric results, and our activities in accordance with the Gaia Alerts (Gaia-FUN-TO).
Non-formal education in astronomy
Ivo Jokin
Municipal center for extracurricular activities
ivo_jokin@abv.bg
ADVECTION– fundamental mechanism
Krasimira Yankova
Space Research and Technology Institute -BAS
f7@space.bas.bg
In this paper we trase the extension on advective hypothesis in GR with purpose an advection affirmation as a fundamental mechanism. We will looking the for connections between the advection and the space-time metrics. We proposed Fundamental Advecton like as base mechanism to the unification of the model accretion in the AGN and non-ACTIVE(sleeping) galactic nucleuses. That allows in the research process on the evolution of the quasars we to get a test method for the new theory.
Evidences for spectral variability of the stable shell star HD 192954
Lubomir Iliev
Institute of Astronomy and NAO, Bulgarian Academy of Sciences
liliev@astro.bas.bg
Based on homogenious high resolution observations new evidences are presented for the spectral activity of the star HD192954, member of the group of stable shell stars. Various estimations are performed with the aim to determine the scale and time span of spectral variations.
Stellar maps of the Northern Sky
Lyuba D. Dankova
Institute of Astronomy and NAO, BAN
5amaltea5@gmail.com
The Northern Sky is presented on 9 maps with the aim of satisfying education and amateur necessities. The position of stars down to 5-th mag, are tinted in accordance with the color of the star, as well as remarkable stellar clusters and galaxies are shown. The coordinates correspond to Epoch 2000.0.
IAU 100 Year Celebration in Bulgaria
Lyuba Slavcheva-Mihova
Institute of Astronomy and NAO, Bulgarian Academy of Sciences
lslavcheva@nao-rozhen.org
Bulgaria is taking a very active part in celebrating the centennial International Astronomical Union (IAU) anniversary. About 120 events are organized in about 20 venues, distributed throughout the country. Covered are practically all IAU100 projects - “100 Hours of Astronomy”, “Women and Girls in Astronomy”, “Dark Skies for All”, “Moon Landing 50th Anniversary”, “Eratosthenes100”, “ 100 Years of General Relativity: Eclipse”. There are events intended for disadvantaged, too. In particular, a total of about 1700 people took part in 6 individual '100 Hours of Astronomy' events organized in 5 different venues in Bulgaria with an overall duration of about 30 hours. Apart from the IAU100 themes, planned are popular presentations, observations, demonstrations, games for children, competitions, shows, concerts, conferences, cinema shows, etc. by the universities, observatories, and planetaria throughout the year. The “Above and Beyond” exhibition can be seen online. Besides, first exposed in the “100 Hours of Astronomy” event (Jan. 12, Sofia), it has already started as a traveling exhibition in about 20 venues. The above information, including the “Above and Beyond” traveling exhibition timetable can be seen on the webpage dedicated to the celebration in Bulgaria: http://www.astro.bas.bg/IAU100/.
Star Formation in Mrk 477
Lyuba Slavcheva-Mihova
Institute of Astronomy and NAO, Bulgarian Academy of Sciences
lslavcheva@nao-rozhen.org
Mrk 477 is considered the closest obscured quasar, a type II ultra luminous Infrared galaxy (ULIRG). This class of objects could be linked to QSOs by the evolutionary sequence, originally proposed by Sanders (1988). According to it a major merger of gas-rich galaxies triggers both intense star formation and quasar activity and the resulting system is classified as a ULIRG. We build the IR-to-UV spectral energy distribution (SED) of Mrk 477; a circum-nuclear region (CNR) SED is also constructed involving high-resolution data. The SEDs are fitted with the AGNfitter code accounting for the emission accretion disk, torus, host galaxy stellar population, and cold dust related to the star formation (SF) regions. Structure and colour maps are also created. Thus, we estimate the SF parameters (history, age, rate, etc.) of Mrk 477 accounting for the active nucleus, less pronounced in the case of type II objects. The results prompt a powerful SF in the CNRs. The relation between the SF and active galactic nucleus (AGN) parameters is studied. Based on high-resolution data, we search for signatures of AGN feedback on star formation.
Research on the white-light solar corona and active solar processes during total solar eclipses
Ts. Tsvetkov, E. Ivanov, R. Miteva, N. Petrov, V. Popov
Institute of Astronomy and NAO, BAS
nip.sob@gmail.com
There are still no sufficient answers to the questions related to: appearance, instability and periodicity of the solar magnetic field, the processes of solar coronal heating and the acceleration of the solar wind, the reasons behind the solar flares, and the processes of accretion of the interplanetary matter. Here we present our project that aims to proffer further investigations and analysis of questions still widely discussed. They are related to the dynamics of active processes in the solar corona both during total solar eclipses and out of them. We live in an era where scientific studies of the Sun and the solar-terrestrial interactions, being done by the above mentioned ground-based and orbital observatories, are more improved and wide-spread. However the total solar eclipses are still a cosmic laboratory impossible to simulate on Earth and they provide a chance for detailed studies of the corona and the active processes happening in it which affect our everyday lives.
The variable H42 in the M31 stellar complex OB81
Nina Taneva
Sofia university
nkoleva@phys.uni-sofia.bg
Photometric BVR data from the Rozhen telescopes obtained in 2018 and R and g-band from Palomar Transient Factory (http://www.ptf.caltech.edu) obtained in 2010-2015 have been used to construct the light curve and to redetermine the period of the variable H42 in the M31 stellar complex OB81.
What extent are double stars really binaries to?
R. Pavlovic, Z. Cvetkovic, G. Damljanovic, M.D. Jovanovic, S. Boeva and G. Latev
Astronomical Observatory, Belgrade, Serbia
rpavlovic@aob.rs
On the basis of the CCD frames, collected from 2013 till now and obtained with the telescopes of ASV and NAOR, of double stars for which there exist orbital or linear elements we have identified both components in the Gaia DR2 Catalogue. Since in that catalogue precisely determined parallaxes for both components are contained, we have compared them in order to establish how much they are really close to each other in space. In this way the question of which double stars are really binaries, i. e. gravitationally bound pairs, can be answered more reliably.
Light curve of 15691 Maslov asteroid
Svetlana Boeva
IA and NAO, BAS
sboeva@astro.bas.bg
Photometric observations of asteroid 15691 Maslov, with duration of 8 hours, were performed with 2 m and 50/70 cm Schmidt telescope at NAO Rozhen. The light curve showed amplitude of 0.3 magnitudes and probably its rotation period was about 7 hours. The color indices of the asteroid indicate that 15691 Maslov belongs to the S spectral type.
Dust released by artificial cosmic impacts: observational challenges
Tanyu Bonev
Institute of Astronomy and NAO
tbonev@astro.bas.bg
In the approaching active phase of The Double Asteroid Redirection Test (DART) mission it is of great interest to make quantitative estimation of the possible consequences of the kinetic impact. Some of the possible outcomes depend on the physical characteristics of the target, the Didymos’ moonlet. In particular, the answer of the question “Will the impact be gravitation dominated or strength dominated?” depends on the surface properties of the moonlet. Most detailed information, concerning these properties, will be obtained from ground based observations in a follow up world-wide campaign, which will last several months after the impact in June 2022. The ground based observations after the impact include astrometry, and imaging of the cloud of dust particles excavated by the impact. For the analysis of data, obtained from the ground, I will make use of the knowledge gained from the analysis of post-impact ground based observations obtained several days after the Deep Impact event in 2005. In order to distinguish the post-impact properties of the Didymos binary system from its pre-impact state it is necessary to perform observations during the next years. Visibility windows for observations of Didymos from NAO Rozhen in the years before the encounter in June 2022 are calculated and plans of different modes of observations will be presented. This research is performed with financial support by the Bulgarian National Science Fund under contract 18/13 – 12.12.2017.
Intra-night flickering of RS Ophiuchi: IV. Shapes of the repeating structures and their evolution (Poster II).
Ts. Georgiev, R. Zamanov, S. Boeva, G. Latev, B. Spassov, J. Martí, G. Nikolov, S. Ibryamov, S. Tsvetkova, K. Stoyanov
Institute of astronomy and NAO
tsgeorg@astro.bas.bg
The flickering of the recurrent nova RS Oph is studied by 58 flickering light curves (FLCs), taken by 5 telescopes in 2008 - 2017. In our recent work 97 flickering quasi-periods (FQPs) were detected by local minima of structure functions and local maxima of auto-correlation functions. Many FLCs show repeating time structures with some FQPs and some morphologies (shapes). In this work we select 25 FLCs (12 in B band and 13 in V band) with monitoring times 46 – 470 min, where the main time structures with FQPs 16 – 56 min repeat themselves 3 – 7 times, changing to some extent their shapes. (i) We derive combined shape for every such monitoring and characterize them by 3 morphological parameters. The amplitudes of the shapes exceed the standard deviation of their profiles 0.85 – 2.01 times. (ii) In the years the skewness (asymmetry) of the shapes vary approximately gradually from positives to negatives. The shapes are approximately symmetric in 2014.
Measurement comparison between CCD frames obtained at NAOR and ASV
Z. Cvetkovic, R. Pavlovic, S. Boeva, Damljanovic, M.D. Jovanovic and G. Latev, G.
Astronomical Observatory Belgrade, Serbia
zorica@aob.rs
During the night of March 31, 2019 we performed CCD framing for 25 double stars with the 2m NAOR telescope. CCD frames for the same stars have been also obtained with the 1.4 m ASV telesccope, during two nights, April 1 and 2, 2019. The CCD cameras are of the same type, ANDOR iKon-L, possessed by both observatories. In the paper a comparison of the results is presented concerning separations and position angle, measurements of the CCD frames obtained at the two observatories. We also present precise focal lengths for the 2m and 1.4m telescopes with the attached ANDOR iKon-L cameras.