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    Öğe
    A Comprehensive Study of the Eclipsing Binaries V1241 Tau and GQ Dra
    (Copernicus Foundation Polish Astronomy, 2020) Ulas, B.; Gazeas, K.; Liakos, A.; Ulusoy, C.; Stateva, I; Erkan, N.; Napetova, M.
    We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curve analyses combined with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the O-C analyses of the systems and we propose the most likely orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a delta Set type pulsator with a dominant pulsation frequency of 18.58 d(-1) based on our B filter residual light curve although it cannot be verified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behavior for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated. Their locations within evolutionary diagrams are compared with other Algol-type systems.
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    Öğe
    A study of variability of the marginal Am star HD 176843 observed in the Kepler field
    (Elsevier Science Bv, 2019) Ulusoy, C.; Stateva, I.; Ulas, B.; Alicavus, F.; Iliev, I. Kh.; Napetova, M.; Kaygan, E.
    We present results of a study of variability of the marginal Am star HD 176843 observed in the Kepler field. Kepler photometry and ground-based spectroscopy are used to investigate the light variations of the star. HD 176843 is classified as a marginal Am star that shows delta Sct type pulsations. From an analysis of the Kepler time series, we find that the light curve of HD 176843 is dominated by three modes with frequencies f(1) = 0.1145, f(2) = 0.0162 and ,f(3) = 0.1078 d(-1). The amplitude of the radial velocity variations of about 10 km/s is much more than the radial velocity errors and allows us to conclude clear radial velocity variations. Using the radial velocity data and the adopted spectra, the orbital solution of HD 176843 is also obtained with an orbital period of 34.14 days. However, the available photometric data show no significant evidence for any possible motion in the binary system.