Перегляд за Автор "Chinarova, L. L."

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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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    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.
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    "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"
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    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
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    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”.
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    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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    WAVELET ANALYSIS OF 173 SEMI-REGULAR VARIABLES
    (Astroprint, 2010) Chinarova, L. L.
    We made the wavelet analysis of 173 semi-regular pulsating variable stars of di erent sub-types. For the analysis, we have used 1,000,000 individual brightness estimates from the published international databases of the VSOLJ (Japan) and AFOEV (France). They were visually checked using the program OL (I.L.Andronov, 2001OAP....14..255A), and bad points were removed from the data les. The wavelet analysis was performed using the program WWZ (I.L.Andronov, 1998KFNT...14..490A) which improves the discrete Morlet-type wavelet transform to the case of irregularly spaced data. Mean weighted wavelet periodograms are presented, as well as wavelet maps. Dependences of the wavelet-based periods and amplitudes on time are presented for the investigated stars. Some stars exhibit switchings between preferred periods, which are interpreted as switchings of the pulsation mode. Additional criteria for classi cation of the pulsating variables based on the stability of periods and amplitudes are discussed. Results are shown for the semi-regular star RU And, for which the semi-amplitude varies drastically from 0.027 (\nearly constant star") to 1.204 mag (\Mira"- type pulsating variable. The phase of pulsations also varies drastically by 0.7P, and the wavelet estimates of the period - from 210 to 270 days.