Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Author: search.filters.author.Keskin, VarolCOAR Access Rights: search.filters.coarAccessRights.open access

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Close Binary System Go Cyg
    (Elsevier Ltd., 2012) Ulaş, Burak; Kalomeni, Belinda; Keskin, Varol; Köse, O.; Yakut, Kadri
    In this study, we present long term photometric variations of the close binary system GO Cyg. Modelling of the system shows that the primary is filling Roche lobe and the secondary of the system is almost filling its Roche lobe. The physical parameters of the system are M1 = 3.0 ± 0.2M ⊙, M2 = 1.3 ± 0.1M⊙, R 1 = 2.50 ± 0.12R⊙, R2 = 1.75 ± 0.09R⊙, L1 = 64 ± 9L ⊙, L2 = 4.9 ± 0.7L⊙, and a = 5.5 ± 0.3R⊙. Our results show that GO Cyg is the most massive system near contact binary (NCB). Analysis of times of the minima shows a sinusoidal variation with a period of 92.3 ± 0.5 yr due to a third body whose mass is less than 2.3M⊙. Finally a period variation rate of -1.4 × 10-9 d/yr has been determined using all available light curves.
  • Article
    Citation - WoS: 30
    Citation - Scopus: 32
    The Short-Period Low-Mass Binary System Cc Com Revisited
    (John Wiley and Sons Inc., 2011) Köse, O; Kalomeni, Belinda; Keskin, Varol; Ulaş, Burak; Yakut, Kadri
    In this study we determined precise orbital and physical parameters of the very short-period low-mass contact binary system CC Com. The parameters are obtained by analysis of new CCD data combined with archival spectroscopic data. The physical parameters of the cool and hot components are derived as Mc = 0.717(14) M⊙, Mh = 0.378(8) M⊙, Rc = 0.708(12) R⊙, Rh = 0.530(10) R⊙, Lc = 0.138(12) L⊙, and Lh = 0.085(7) L⊙, respectively, and the distance of the system is estimated as 64(4) pc. The times of minima obtained in this study and with those published before enable us to calculate the mass transfer rate between the components which is 1.6 × 10-8 M⊙ yr-1. Finally, we discuss the possible evolutionary scenario of CC Com.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 8
    Marginally Low Mass Ratio Close Binary System V1191 Cyg
    (Elsevier Ltd., 2012) Ulaş, B.; Kalomeni, Belinda; Keskin, Varol; Köse, O.; Yakut, Kadri
    In this study, we present photometric and spectroscopic variations of the extremely small mass ratio (q ≃ 0.1) late-type contact binary system V1191 Cyg. The parameters for the hot and cooler companions have been determined as Mh = 0.13 (1) M⊙, Mc = 1.29 (8) M ⊙, Rh = 0.52 (15) R⊙, Rc = 1.31 (18) R⊙, Lh = 0.46 (25) L⊙, Lc = 2.71 (80) L⊙, the separation of the components is a = 2.20 (8) R⊙ and the distance of the system is estimated as 278 (31) pc. Analyses of the times of minima indicates a period increase of dPdt=1.3(1)×10-6days/yr that reveals a very high mass transfer rate of dMdt=2.0(4)×10-7M⊙/yr from the less massive component to the more massive one. New observations show that the depths of the minima of the light curve have been interchanged. © 2011 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 37
    Citation - Scopus: 36
    Absolute Properties of the Binary System Bb Pegasi
    (IOP Publishing, 2007) Kalomeni, Belinda; Yakut, Kadri; Keskin, Varol; Değirmenci, Ömer Lütfi; Ulaş, Burak; Köse, Oğuzhan
    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) × 10-8 days yr -1. This period increase of BB Peg can be interpreted in terms of the mass transfer 2.4 × 10-8 M⊙ yr-1 from the less massive to the more massive component. The physical parameters have been determined as Mc = 1.42M⊙, Mh = 0.53 M⊙, Rc = 1.29 R⊙, Rh, = 0.83 R⊙, Lc = 1.86 L⊙, and L h = 0.94 L⊙ 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.