Yazar "Degirmenci, O. L." seçeneğine göre listele

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    Öğe
    Absolute properties of the binary system BB Pegasi
    (Univ Chicago Press, 2007) Kalomeni, B.; Yakut, K.; Keskin, V.; Degirmenci, O. L.; Ulas, B.; Kose, O.
    We present ground-based photometry of the low-temperature contact binary BB Peg. We collected all the times of mid-eclipse available in the literature and combined them with those obtained in this study. Analyses of the data indicate a period increase of (3.0 +/- 0.1) x 10(-8) days yr 1. This period increase of BB Peg can be interpreted in terms of the mass transfer 2.4 x 10(-8) Mo yr(-1) from the less massive to the more massive component. The physical parameters have been determined as M-c, = 1.42 Mo, My, = 0.53 Mo, R-c, = 1.29 Ro, Rh = 0.83 R-circle dot, L-c, = 1.86 L-c, and L-h = 0.94 L-circle dot through simultaneous solutions of light and of the radial velocity curves. The orbital parameters of the third body, which orbits the contact system in an eccentric orbit, were obtained from the period variation analysis. The system is compared to the similar binaries in the Hertzsprung-Russell and mass-radius diagrams.
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    Öğe
    First ground-based photometry and light-curve analysis of the eccentric eclipsing binary V744 Cas
    (Wiley-V C H Verlag Gmbh, 2006) Bulut, I.; Cicek, C.; Erdem, A.; Bakis, V.; Demircan, O.; Degirmenci, O. L.
    The first ground-based BVR photometric observations of the recently discovered eclipsing binary V744 Cas are presented. From these measurements, timings for two primary and one secondary minima have been calculated. The light curves of the system were analyzed by using the Wilson-Devinney program. The analysis shows that the system is detached with two similar components of spectral type A2V, and the orbit is eccentric (e = 0.0662 +/- 0.0005). The longitude of the periastron (w) was found significantly different for two different light curves (ours and that of Hipparcos), which is strongly suggestive of an apsidal motion with a period of about 425 +/- 68 yr. This makes V744 Cas an important candidate for studies of apsidal motions. The first estimate of the absolute dimensions place the system close to the terminal age of the main sequence (TAMS) in the HR diagram. The distance from the spectroscopic parallax (d = 740 +/- 10 pc) was found to be slightly larger than the Hipparcos distance of d = 610 +/- 400 pc. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Öğe
    The first BVR light curves and period analysis of the eclipsing binary V821 Cas
    (Elsevier Science Bv, 2007) Degirmenci, O. L.; Bozkurt, Z.; Yakut, K.; Demircan, O.; Erdem, A.; Cicek, C.; Bulut, I.
    The first BVR light curves of the eclipsing binary V821 Cas are used to derive the physical parameters of the system. The light curves were obtained during 2000 and 2001 observational seasons at Ege University Observatory (EUO). Period variation of the system was also investigated. For the first time apsidal motion elements of the system were obtained from the O-C curve analyses. Preliminary absolute parameters of the components were computed taking into account the results of light curves analysis. Observational and theoretical internal structure constants were estimated to be log (k) over bar (2obs) = -2.66 and log (k) over bar (2,theo) = -2.42, respectively.(c) 2006 Elsevier B.V. All rights reserved.