Yazar "Yakut, K." seçeneğine göre listele

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  • [ X ]
    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.
  • [ X ]
    Öğe
    Modelling the components of binaries in the Hyades: the dependence of the mixing-length parameter on stellar mass
    (Oxford Univ Press, 2006) Yildiz, M.; Yakut, K.; Bakis, H.; Noels, A.
    We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to observations so as to give the observed total V and B-V of that system and the observed slope of the main sequence in the corresponding parts. According to our findings, there is a very definite relationship between the mixing-length parameter and the stellar mass. The fitting formula for this relationship can be given as alpha = 9.19 (M/M-circle dot-0.74)(0.053)-6.65, which is valid for stellar masses greater than 0.77 M-circle dot. While no strict information is gathered for the chemical composition of the cluster, as a result of degeneracy in the colour-magnitude diagram, by adopting Z = 0.033 and using models for the components of 70 Tau and theta(2) Tau we find the hydrogen abundance to be X = 0.676 and the age to be 670 Myr. If we assume that Z = 0.024, then X = 0.718 and the age is 720 Myr. Our findings concerning the mixing-length parameter are valid for both sets of the solution. For both components of the active binary system V818 Tau, the differences between radii of the models with Z = 0.024 and the observed radii are only about 4 per cent. More generally, the effective temperatures of the models of low-mass stars in the binary systems studied are in good agreement with those determined by spectroscopic methods.
  • [ X ]
    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.