Yazar "Gunes, M." seçeneğine göre listele

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    Dynamic Evolution of the Eclipsing Overcontact Binary Star System BI CVn
    (Iop Publishing Ltd, 2025) Bulut, I.; Gunes, M.; Nehir, C.
    We present a comprehensive analysis of BI CVn, an eclipsing overcontact binary system. New BVR photometric observations, combined with available spectroscopic data, were analyzed simultaneously using the Wilson-Devinney method to derive the orbital and physical parameters of the system. The resulting stellar parameters are M-1 = 0.58 +/- 0.01M(circle dot), M-2 = 1.42 +/- 0.02M(circle dot), R-1 = 0.88 +/- 0.01R(circle dot), R-2 = 1.31 +/- 0.01R(circle dot), with an orbital separation of a = 2.80 +/- 0.01R(circle dot). Based on all available CCD times of minimum light, including both ground-based and TESS observations, the (O - C) diagram of BI CVn was analyzed. The orbital period exhibits a long-term decrease at a rate of -2.3239 (+/- 0.0001) x 10(-8) day yr(-1), likely due to mass transfer from the more massive to the less massive component. Superimposed on this trend is a cyclic variation with a period of 56.84 +/- 0.08 yr, indicative of a light-travel time effect caused by a third body, whose estimated mass is 0.63 +/- 0.02M(circle dot). Using these derived parameters, we modeled the binary's evolution through non-conservative processes with the Binary Star Evolution code. The evolutionary tracks of the components were examined in multiple parameter planes, leading to an estimated merger timescale of approximately 2.70 Gyr.
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    Light curve analysis of a new W UMa system GSC 3581-1856
    (Elsevier Science Bv, 2018) Bulut, I.; Bulut, A.; Gunes, M.; Demircan, O.
    New BVRI photometric observations covering seven minima times for the eclipsing binary GSC 3581-1856 were presented. The light curves in BVRI colours were analysed by using PHOEBE code for the system parameters. New minima times were used in revising the light elements. The system is found a W-type contact binary with mass ratio of q = 1.3362 +/- 0.0042 and a fill out parameter of f = 16.89 +/- 3.17%. The smaller and less massive component was found hotter component (T-1 similar or equal to 5590 K). Lower temperature (T-2 = 5295 K) of the mass accreting more massive component is probably due to a disk or envelope around this star. The original temperature of the more massive secondary component would be at least T-2 similar or equal to 5590K. The preliminary absolute dimensions (M-1 = 0.78 +/- 0.01 M-circle dot, M-2 = 1.05 +/- 0.01 M-circle dot, R-1 = 0.92 +/- 0.10 R-circle dot, R-2 = 1.05 +/- 0.20 R-circle dot, L-1 = 0.86 +/- 0.20 L-circle dot and L-2 = 1.00 +/- 0.20 L-circle dot) indicate a relatively young marginal contact binary for GSC 3581-1856 system. The present luminosity of the less massive but hotter component would be not much different from its main sequence luminosity, and thus its original mass was estimated to be slightly more than one solar mass. This means it could be transferred and/or lost about 30% of its original mass which place the system in relatively young system in contact phase. (C) 2017 Elsevier B.V. All rights reserved.