Репозитарій ОНУ імені І.І.Мечникова

Перегляд за Автор "Andronov, Ivan L."

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A technique for simultaneous measurement of circular and linear polarization with a single-channel polarimeter
(Одеський національний університет імені І. І. Мечникова, 2016) Kolesnikov, S. V.; Breus, V. V.; Kiselev, N. N.; Andronov, Ivan L.
We present a technique for simultaneous measurement of circular and linear polarization with the single-channel polarimeter, that is used in Crimean astrophysical observatory for many years. Methods and a computer program for data reduction is described. The algorithm is described, which have been used for photo-polarimetric monitoring of various astronomical objects cataclysmic variables, asteroids, comets.
A technique for simultaneous measurement of circular and linear polarization with a single-channel polarimeter
(Одеський національний університет імені І. І. Мечникова, 2016) Kolesnikov, S. V.; Breus, V. V.; Kiselev, N. N.; Andronov, Ivan L.
We present a technique for simultaneous measurement of circular and linear polarization with the single-channel polarimeter, that is used in Crimean astrophysical observatory for many years. Methods and a computer program for data reduction is described. The algorithm is described, which have been used for photo-polarimetric monitoring of various astronomical objects cataclysmic variables, asteroids, comets.
”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.
CCD OBSERVATIONS OF THE INTERMEDIATE POLAR MU CAM AND GSC 04370-00206
(Astroprint, 2010-07) Chinarova, L. L.; Andronov, Ivan L.; Gubin, E. G.
Results of CCD observations of MU Cam and GSC 04370-00206 obtained at the 60 cm telescope of the RSI \Astronomical Observatory" of the Odessa National University.
Determination of size of the emitting region in eclipsing cataclysmic variable stars
(Astroprint, 2014) Andronov, Ivan L.; Andrych, K. D.
The dependencies of the phase of eclipse of the white dwarf’s centre and the durations of the ascending and descending branches of the light curve on the binary system’s parameters were computed using the sphericallysymmetric approximation and the more accurate model of the elliptical projection onto the celestial sphere of the companion (red dwarf) that fills its Roche lobe. The parameters of eclipses in the classical eclipsing polar OTJ 071126+440405 = CSS 081231:071126+440405 were estimated.
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.
Improved mathematical modeling of the angular size of the Roche lobe
(Odessa I.I. Mechnikov National University, 2009) Andronov, Ivan L.; Breus, Vitalii V.
"INTER-LONGITUDE ASTRONOMY" (ILA) PROJECT: CURRENT HIGHLIGHTS AND PERSPECTIVES. I. MAGNETIC VS. NON-MAGNETIC INTERACTING BINARY STARS
(Astroprint, 2010-07) Andronov, Ivan L.; Antoniuk, K. A.; Baklanov, A. V.; Breus, V. V.; Burwitz, V.; Chinarova, L. L.; Chochol, D.; Dubovsky, P. A.; Han, W.; Hegedus, T.; Henden, A.; Hric, L.; Kim, Chun-Hwey; Kim, Yonggi; Kolesnikov, S. V.; Kudzej, I.; Liakos, A.; Niarchos, P. G.; Oksanen, A.; Patkos, L.; Petrik, K.; Pit, N. V.; Shakhovskoy, N. M.; Virnina, N. A.; Yoon, J.; Zola, S.
We present a review of highlights of our photometric and photo-polarimetric monitoring and mathematical modeling of interacting binary stars of di erent types classical, asynchronous, intermediate polars with 25 timescales corresponding to di erent physical mechanisms and their combinations (part "Polar"); negative and positive superhumpers in nova-like and dwarf novae stars ("Superhumper"); symbiotic ("Symbiosis"); eclipsing variables with and without evidence for a current mass transfer ("Eclipser") with a special emphasis on systems with a direct impact of the stream into the gainor star's atmosphere, which we propose to call "Impactors", or V361 Lyr-type stars. Other parts of the ILA project are "Stellar Bell" (pulsating variables of di erent types and periods - M, SR, RV Tau, RR Lyr, Delta Sct) and "New Variable"
Mathematical modeling of the photometric variability of three newly discovered variable stars
(Odessa I.I. Mechnikov National University, 2009) Andronov, Ivan L.; Virnina, Natalia A.
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.
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.
Revision of the phenomenological characteristics of the algol-type stars using the nav algorithm
(Одеський національний університет імені І. І. Мечникова, 2015) Tkachenko, M. G.; Andronov, Ivan L.; Chinarova, L. L.
Phenomenological characteristics of the sample of the Algol – type stars are revised using a recently developed NAV (“New Algol Variable”) algorithm (2012Ap.....55..536A, 2012arXiv 1212.6707A) and compared to that obtained using common methods of Trigonometric Polynomial Fit (TP) or local Algebraic Polynomial (A) fit of a fixed or (alternately) statistically optimal degree (1994OAP.....7...49A, 2003ASPC..292..391A). The computer program NAV is introduced, which allows to determine the best fit with 7 “linear” and 5 “nonlinear” parameters and their error estimates. The number of parameters is much smaller than for the TP fit (typically 20 – 40, depending on the width of the eclipse, and is much smaller (5 – 20) for the W UMa and  Lyrae – type stars. This causes more smooth approximation taking into account the reflection and ellipsoidal effects (TP2) and generally different shapes of the primary and secondary eclipses. An application of the method to two – color CCD photometry to the recently discovered eclipsing variable 2MASS J18024395 + 4003309 = VSX J180243.9 +400331 (2015JASS...32..101A) allowed to make estimates of the physical parameters of the binary system based on the phenomenological parameters of the light curve. The phenomenological parameters of the light curves were determined for the sample of newly discovered EA and EW – type stars (VSX J223429.3+552903, VSX J223421.4+553013, VSX J223416.2+553424, USNO- B1.0 1347-0483658, UCAC3-191-085589, VSX J180755.6+074711= UCAC3 196-166827). Despite we have used original observations published by the discoverers, the accuracy estimates of the period using the NAV method are typically better than the original ones
Statistically optimal modeling of Flat eclipses and Exoplanet transitions. The “Wall-Supported polynomial” (WSP) algoritms
(Одеський національний університет імені І. І. Мечникова, 2017) Andrych, K. D.; Andronov, Ivan L.; Chinarova, L. L.
The methods for determination of the characteristics of the extrema are discussed with an application to irregularly spaced data, which are characteristic for photometrical observations of variable stars. We introduce new special functions, which were named as the “Wall-Supported Polynomial” (WSP) of different orders. It is a parabola (WSP), constant line (WSL) or an “asymptotic” parabola (WSAP) with “walls” corresponding to more inclined descending and ascending branches of the light curve. As the interval is split generally into 3 parts, the approximations may be classified as a “nonpolynomial splines”.
TWO-COMPONENT VARIABILITY OF THE SEMI-REGULAR PULSATING STAR U DELPHINI
(Astroprint, 2012) Andronov, Ivan L.; Chinarova, L. L.
ABSTRACT. Photometric analysis of photometric variability of the semi-regular pulsating variable U Del is analyzed. From the international AFOEV database, 6231 brightness values in the time interval JD 2451602-55378 were chosen. For the periodogram analysis, we have used a trigonometric polynomial fit. Using the criterion of minimal variance of the approximation at arguments of observations, the optimal degree is s=1. Initial epoch for maximum is T0=JD2453340±3, the period P=1198±4 . Mean brightness at maximum is 6.624 d±0.005, at minimum 7.124±0.005, i.e. the amplitude is 0.499±0.005m. Besides this slow variability, there is a faster oscillation of a period of 119.45±0.06d, amplitude 0.303±0.005 and an initial epoch for maximum 2453215.1m±0.5. These results are mean during the time interval after that analyzed in the catalogue of Chinarova and Andronov (2000). Also the method of “running sines” with a filter half-width Δt=0.5P. The local mean (averaged over a short period) brightness varies in a range 6.58-7.41 , the semiamplitude exhibits very strong variations from 0.01 to 0.46 . The phase is also variable – typically of a full amplitude of 0.5. Close to JD 2452589, occurred a phase jump by a complete period during a descending branch of a slow wave. This effect was not observed during other cycles. No significant correlation between mean brightness and amplitude of short-period oscillation was found. Despite significant variability of amplitude, the periodic contribution is not statistically significant. Also characteristics of individual brightness extrema were found. m m The study was made in a course of the international project “Inter-Longitude Astronomy" (Andronov et al., 2010) and national project "Ukrainian Virtual Observatory(Vavilova et al., 2012).

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