Перегляд за Автор "Marsakova, V. I."

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    ”Asymptotic parabola” fits for smoothing generally asymmetric light curves
    (Одеський національний університет імені І. І. Мечникова, 2015) Andrych, K. D.; Andronov, Ivan L.; Chinarova, L. L.; Marsakova, V. I.
    A computer program is introduced, which allows to determine statistically optimal approximation using the "Asymptotic Parabola" fit, or, in other words, the spline consisting of polynomials of order 1,2,1, or two lines ("asymptotes") connected with a parabola. The function itself and its derivative is continuous. There are 5 parameters: two points, where a line switches to a parabola and vice versa, the slopes of the line and the curvature of the parabola. Extreme cases are either the parabola without lines (i.e.the parabola of width of the whole interval), or lines without a parabola (zero width of the parabola), or "line+parabola" without a second line. Such an approximation is especially effective for pulsating variables, for which the slopes of the ascending and descending branches are generally different, so the maxima and minima have asymmetric shapes. The method was initially introduced by Marsakova and Andronov (1996OAP.....9...127M) and realized as a computer program written in QBasic under DOS. It was used for dozens of variable stars, particularly, for the catalogs of the individual characteristics of pulsations of the Mira (1998OAP....11...79M) and semi-regular (200OAP....13..116C) pulsating variables. For the eclipsing variables with nearly symmetric shapes of the minima, we use a "symmetric" version of the "Asymptotic parabola". Here we introduce a Windows-based program, which does not have DOS limitation for the memory (number of observations) and screen resolution. The program has an user-friendly interface and is illustrated by an application to the test signal and to the pulsating variable AC Her.
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    CHARACTERISTICS OF THE PERIOD CHANGES IN MIRA-TYPE VARIABLES
    (Astroprint, 2014) Marsakova, V. I.
    The period changes in a sample of Miratype variables were analysed and classified. Characteristics of the long-term cyclicity in the period changes were obtained.
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    Effects of the mass transfer and presence of the third components in close binary stellar systems
    (Одеський національний університет імені І. І. Мечникова, 2017) Tvardovskyi, D. E.; Marsakova, V. I.; Andronov, Ivan L.
    In our research, we have studied 6 close binary stellar systems which are eclipsing variables of β Lyrae and W Ursae Majoris types of variability. We have studied their O-C curves. To build them, we used moments of minima, listed in the BRNO database. Also, we used ones, which we obtained as the result of processing of observational data taken from AAVSO database. As the result of the O-C analysis, we detected that all of these stars have parabolic O-C curves, which might be caused by mass transfer from one component to another. In an addition, 3 from researched stars (U Peg, V0523 Cas and WZ Cyg) have superimposed parabolic and cyclic O-C changes that could be caused by presence of the third components in the systems. Also, we calculated minimal possible masses of third components, rates of the mass transfer for these systems and corrected the ephemerides.
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    Improved ephemeris of poorly studied eclipsing binary GSC 3950-00707 = 2MASS J20355082+5242136
    (Одеський національний університет імені І. І. Мечникова, 2017) Savastru, S. V.; Marsakova, V. I.; Andrych, K. D.; Dubovsky, P. A.
    We made our CCD-observations of GSC 3950-00707 by using the telescope Celestron-14 of Vihorlat Observatory and Astronomical Observatory on Kolonica Saddle. The moments of minima were calculated by using the symmetrical polynomial fit. We also analyzed the observations from automated surveys ASAS-SN and found 3 mean minima by using trigonometrical polynomial fit. The analysis of our observations and data from the surveys allows to conclude that it is the W UMa-type variable and its published period value is not accurate. We analyzed the O-C curve and corrected the elements.
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    LIGHT POLLUTION IN LEO-SATELLITE TRACKING
    (Astroprint, 2015) Shakun, Leonid S.; Marsakova, V. I.; Golubovskaya, T. A.; Terpan, S. S.; Melikyants, S. M.; Korobeinikova, E. A.
    Because of the high level of the light pollution in Odessa city, only the observations of LEO (low Earth orbit)-satellites are performed in the main office of the Astronomical observatory of Odessa National University named after I.I. Mechnikov. As the one of the observation results we obtain the sky background measurements along the satellite’s way through the sky (at different azimuths and altitudes that change during the satellite tracking). We propose the method of irregular extinction changes diagnostics that realized by using the different data filtration methods. Also as the result of our analysis of these observations we present azimuth-altitude diagram of sky background that shows the most significant light pollution at the north-western and northern directions caused by the Port of Odessa and the stadium “Chernomorets”.
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    MIRAS OR SRA’S – THE TRANSIENT TYPE VARIABLES
    (Astroprint, 2012) Marsakova, V. I.; Andronov, Ivan L.
    The variability of several stars shows “Mira-type” and “semiregular” behavior during long-time data ranges. Such data are available due to amateur visual observations from AAVSO and AFOEV databases. We have studied these properties by using different methods of timeseries analysis, such as the periodogram analysis using trigonometric polynomial fit, wavelet analysis and individual cycle characteristics analysis using the running parabola fit. As the result, very similar multiperiodicities were detected.
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    Period variations and possible third components in the eclipsing binaries AH Tauri and ZZ Cassiopeiae
    (Одеський національний університет імені І. І. Мечникова, 2018) Tvardovskyi, D. E.; Marsakova, V. I.; Andronov, Ivan L.; Shakun, Leonid S.; Твардовський, Д. Є.; Маршакова, В. І.; Андронов, Іван Л.; Шакун, Леонід С.
    In our research, we investigated two variable stars: AH Tau and ZZ Cas. They are eclipsing binary stars of W Ursae Majories and 􀁅 Lyrae types. The period between eclipses of these stars changes with time. The reason for steady changes of the period could be the mass transfer (the flow of matter) between components of these stellar systems. For ZZ Cas the changes of the period are cyclic. That is why we assume the cyclic changes could be caused by the presence of the hypothetical third component (either a small star or a large planet). The cyclic changes of the period for AH Tau superimpose on steady ones (the period decrease). Thus we assume the third component and mass transfer are present. We also assume that the third components do not take part in the eclipses. However, due to their gravity, they make the visible close binary systems rotate and become closer or further to an observer. This explanation is called Light-Time Effect (LTE). Generally, an orbit of a third component is not a circle, but an ellipse and it is inclined relatively to the observer’s line of sight. Using special plot called O-C curve we estimated the parameters of a third component’s orbit such as a semi-major axis, an eccentricity, angles of orientation and a period of a third component’s rotation. The O-C curve is the plot which shows how the difference between an observed and calculated moment of minimal brightness changes during a long period of time (usually it is several decades). To do this we created a modeling computer program using the computer language Python. In addition, we can calculate errors of third component’s orbit parameters and even estimate its mass. The values of masses of the third components within errors of calculations show that the third components are probably stars. All these calculations were made using all available data from international database BRNO (Brno Regional Network for Observers). Moreover, we used moments of minima which we calculated as the result of observation processing from AAVSO database (American Association of Variable Stars Observers). These results are provided in the tables and plots.
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    T CEP, U UMI, Z SCO – MIRA-TYPE VARIABLES WITH CYCLIC PERIOD CHANGES
    (Astroprint, 2013) Marsakova, V. I.
    ABSTRACT. Period and amplitude changes of three Mira-type variables have been analyzed. Characteristics of long-term cyclicity were obtained.
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    THE QUANTITY AND QUALITY OF OBSERVATIONAL NIGHTS MONITORED WITH USING THE ASTRONOMICAL INSTRUMENTS AT THE SUBURBAN OBSERVATION STATIONS OF ASTRONOMICAL OBSERVATORY OF ODESSA NATIONAL UNIVERSITY
    (Astroprint, 2015) Kashuba, S. G.; Gorbanev, Juri M.; Andrievsky, Serhii M.; Marsakova, V. I.; Troianskyi, V. V.; Андрієвський, Сергій Михайлович; Андриевский, Сергей Михайлович
    The Astronomical Observatory of Odessa National University named after I.I. Mechnikov is one of the four astronomical observatories which exist in classical universities. The Observatory has a main office in the T.G. Shevchenko Park that located near historical center of Odessa. The Observatory also has several observation stations: in the Odessa suburb Mayaki and Kryzhanovka villages.