Yazar "Bulut, Ibrahim" seçeneğine göre listele

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    Absolute Dimensions and Apsidal Motion of the Young Detached System LT Canis Majoris
    (Oxford Univ Press, 2010) Bakis, Volkan; Bulut, Ibrahim; Bilir, Selcuk; Bakis, Hicran; Demircan, Osman; Hensberge, Herman
    New high-resolution spectra of the short-period (P similar to 1.76 days) young detached binary LT CMa are reported for the first time. By combining the results from an analysis of new radial-velocity curves and published light curves, we determine values for the masses, radii, and temperatures as follows: M-1 = 5.59 (0.20)M-circle dot, R-1 = 3.56 (0.07) R-circle dot, and T-eff1 = 17000 (500) K for the primary and M-2 = 3.36 (0.14)M-circle dot, R-2 = 2.04 (0.05) R-circle dot, and T-eff2 = 13140 (800) K for the secondary. Static absorbtion features apart from those coming from the close binary components were detected in the several spectral regions. If these absorbtion features are from a third star, as the light-curve solutions support, its radial velocity is measured to be RV3 = 70 (8) km s(-1) The orbit of the binary system has been proved to be eccentric (e = 0.059) and thus apsidal motion exists. The estimated linear advance in longitude of periastron corresponds to an apsidal motion of U = 69 +/- 5 yr for the system. The average internal structure constant, log k(2,obs) = -2.53 of LT CMa, is found to be smaller than its theoretical value of log k(2,theo) = -2.22, suggesting that the stars would have a more central concentration in mass. The photometric distance of LT CMa (d = 535 +/- 45 pc) is found to be much smaller than the distance of the CMa OB1 association (1150 pc), which rules out membership. A comparison with current stellar evolution models for solar metallicity indicates that LT CMa (35 Myr) is much older than the CMa OB1 association (3 Myr), confirming that LT CMa is not a member of CMa OB1. Kinematical and dynamical analyses indicate that LT CMa is orbiting the Galaxy in a circular orbit, and belongs to the young thin-disk population.
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    Apsidal motion elements of six eccentric eclipsing binaries: V799 Cas, CO Cep, V1136 Cyg, V345 Lac, V364 Lac and V402 Lac
    (Elsevier Science Bv, 2013) Bulut, Ibrahim
    The apsidal motion analysis of the eccentric eclipsing binaries: V799 Cas, CO Cep, V1136 Cyg, V345 Lac, V364 Lac and V402 Lac have been presented. The method described by Lacy (1992) has been used for the apsidal motion analysis. The apsidal motion pericids have been found to be 1229 +/- 235, 64,600 +/- 20,000, 586 +/- 6, 14,240 +/- 2800, 3502 +/- 582 and 242 +/- 60 yr for V799 Cas, CO Cep, V1136 Cyg, V345 Lac, V364 Lac and V402 Lac, respectively. The corresponding internal structure constant, log (k) over bar (2), for V799 Cas, V364 Lac and V402 Lac have been derived and compared to the theoretical values. (C) 2012 Elsevier B.V. All rights reserved.
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    Circumbinary Components of Contact Binaries
    (Astronomical Soc Pacific, 2015) Demircan, Osman; Bulut, Ibrahim
    Period changes in contact binaries obtained by the analysis of times of eclipse are often found to be chaotic in nature. However, they may be representable by a few cyclic changes superposed on a secular change. The cyclic changes are most likely caused by third components revolving around the contact binaries. This contribution shows some typical examples of the period changes in contact binaries.
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    Where Are The Circumbinary Planets of Contact Binaries?
    (Astronomical Soc Pacific, 2015) Demircan, Osman; Bulut, Ibrahim
    To date no circumbinary planets around a contact binary have been discovered, either by the transit method or from eclipse timing variations, even though such binaries are occasionally known to have wide stellar companions. We thus ask: Where are the circumbinary planets of contact binaries? We have simulated the light curves of contact binaries with possible transiting Jovian circumbinary planets considering the available physical and geometric constraints on the system parameters. It would seem that either circumbinary Jovian planets are not formed at all around contact binaries, possibly due to dynamical effects from the binary or third component stars, or that they are present but their discovery has not been possible so far due to larger distortions than expected in the photometric data or in the times of minimum.