Physics / Fizik

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

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Publisher: search.filters.publisher.IOP PublishingSubject: search.filters.subject.Stars

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  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Variation of the Light and Period of the Magnetic Cataclysmic Variable Am Her
    (IOP Publishing, 2008) Kalomeni, Belinda; Yakut, Kadri
    Ground-based, long-term optic variability of AM Her, covering the period between 2003-2008, has been conducted to study the features seen in both low and high states of the system. Low-state analysis shows the presence of short-term, low-amplitude light variations of about 0.02-0.03 mag with a mean power time between 16 s and 226 s. Brightness variations on the order of 0.7-2 mag, which could be due to the stellar activity of the component in the system, are also detected. A total of 30 years' times of minimum light given in the literature are combined with nine times of minima obtained in this study. We represented the (observed-calculated) diagram by a parabolic curve and also by two broken lines. Under the assumption of a parabolic variation, we estimate an increase in period, dP/dt = 7.5(1.2) x 10(-9) days yr(-1), with a mass transfer rate of. M = 8(2) x 10(-9) M(circle dot) yr(-1), in agreement with the previous findings by a different method.
  • 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.