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Öğe A binary star with a ? Scuti component(Univ Chicago Press, 2003) Soydugan, E; Demircan, O; Akan, MC; Soydugan, FNew photometric observations of the Algol-type binary system AB Cassiopeiae were obtained in B and V filters during the 2001-2002 observing season at Ege University Observatory. As expected, the new light curves of the system, which were analyzed using the Wilson-Devinney code, exhibit short-period oscillations due to pulsation of the primary component. A photometric q-value search was performed, and the mass ratio of the system was found to be 0.19. The residuals from the observed-minus-computed light curves of the system reveal the pulsation light curves of the primary component. From the clear cycles of the pulsations in the light curves, we determined 21 new times of maximum light. The frequency content was investigated by using the Period98 program. Although the amplitude variation may suggest multiple periodicity in the pulsations, the power spectrum shows that only one frequency is significant; the remaining frequencies are probably not statistically significant. A multisite campaign is needed in order to study the reliability of the other pulsation modes.Öğe A near-contact binary(Wiley-V C H Verlag Gmbh, 2005) Çiçek, C; Erdem, A; Soydugan, FNew BVR light curves and photometric analysis of the eclipsing binary star CN And are presented. The shape of the light curves are typical of beta Lyr type, and there are large asymmetries between maxima. The BVR light curves and the radial velocity curves (from Rucinski et al. 2000) were solved with the Wilson-Devinney method, simultaneously. The results suggest that CN And is a almost contact binary system, in which the component stars are filling similar to 99% of their Roche lobes. We discuss the model with a large dark starspot on the more massive star and a bright substellar spot on the companion to account for the light curve asymmetries. The absolute parameters of the system were also derived. The system resembles the near contact binary V1010 Oph according to its Roche configuration and light curve asymmetries. We, also, discuss the evolution of the system: it seems to be in a transition phase to the contact era. All previous times of minimum light were collected and combined with the new ones presented in this work. The variation of the orbital period of the system was then analyzed. The results reveal that the orbital period has a secular decrease of about 1.98 +/- 0.04 sec per century, which corresponds to a conservative mass transfer from the more to the less massive component at a rate of (1.52 +/- 0.09) x 10(-7)m(circle dot)/yr or a mass loss from the primary component due to magnetic stellar winds at a rate of (7.83 +/- 0.09) x 10(-8)m(circle dot)/yr.Öğe A new photometric study of CW Cephei and its apsidal motion(Wiley-V C H Verlag Gmbh, 2004) Erdem, A; Soydugan, E; Soydugan, F; Özdemir, S; Çiçek, C; Bulut, I; Demircan, ONew photoelectric observations of the eccentric orbit binary CW Cephei have been carried out in B, V and R colours during the 2000 observing season at TUBITAK (The Scientific and Technical Research Council of Turkey) National Observatory. The light curves of the system were analyzed with a nonsynchronous rotation approach using the method of Wilson-Devinney in B, V and R bands, simultaneously. Especially, we used the R band to check for a third light in the solution as distinct from previous studies. But, the third light contribution in the light curves comes out to be almost negligible. In this study, the values of the longitude of periastron (omega) of the system's orbit found in the solutions of the light curves and radial velocity curves were collected and the variation of w with time was investigated. A new value of the apsidal motion velocity has been obtained as omega=0.0582 +/- 0.0011 (deg/cycle), corresponding to an apsidal period U=46 +/- 1 yr.Öğe A photometric study of the recently discovered eclipsing binary V899 Herculis(E D P Sciences, 2002) Özdemir, S; Demircan, O; Erdem, A; Çiçek, C; Bulut, I; Soydugan, E; Soydugan, FThe radial velocity and UBV light curves of V899 Her as found in the literature were studied for the first time to obtain the orbital parameters and geometry of the system. The solutions obtained by using the Wilson-Devinney code reveal an over-contact system with a fill-out factor of 23.7%. This solution is only possible with a large amount of third light (L-3 approximate to 0.68) which confirms the spectroscopic result obtained by Lu et al. (2001) who reported that the system of which V899 Her is a fainter component is triple, or even quadruple. The distance of the system found by using absolute parameters is comparable with the Hipparcos result.Öğe Catalogue of Algol type binary stars(Edp Sciences S A, 2004) Budding, E; Erdem, A; Çiçek, C; Bulut, I; Soydugan, F; Soydugan, E; Bakis, VA catalogue of (411) Algol-type (semi-detached) binary stars is presented in the form of five separate tables of information. The catalogue has developed from an earlier version by including more recent information and an improved layout. A sixth table lists (1872) candidate Algols, about which fewer details are known at present. Some issues relating to the classification and interpretation of Algol-like binaries are also discussed.Öğe Orbital period changes of ALGOL-type binaries: S Equulei and AB Cassiopeiae(Univ Chicago Press, 2003) Soydugan, F; Demircan, O; Soydugan, E; Ibanoglu, CThe orbital periods of two Algol-type binaries, S Equ and AB Cas, are studied based on all available times of minima. It is found that the O-C variations of both systems can be represented by a parabolic and a periodic term. S Equ has an accretion region due to mass transfer as shown by Richards and coworkers and Richards & Albright. On the other hand, Zola obtained a light-curve solution with a third light. Our study reveals evidence of mass transfer and third component stars in both systems. The parabolic terms in the O-C variations are due to mass transfer from less massive to more massive components, which is consistent with the semidetached nature of both systems. The periodic terms are explained with the additional third stars in the systems. It is interesting that there is no sign of a magnetic braking effect from the cool secondary in the O-C variation of either system.Öğe Photometric study of the binary system V397 cephei(Oxford Univ Press, 2005) Bulut, I; Demircan, O; Budding, E; Erdem, A; Çiçek, C; Esenoglu, H; Soydugan, FThe first ground-based UBV observations (2001, Inf. Bull. Variable Stars, 5129) of V397 Cep were analyzed by using the Wilson-Devinney method, and the results were compared with others in the literature. A consistent geometry with a photometric mass-ratio close to unity and an eccentric orbit of e similar or equal to 0.13 was found. The longitude of the periastron (omega) was found significantly different for two different light curves, which is strongly suggestive of an apsidal motion with a period of about 300 yr. This makes V397 Cep an important candidate for studies of apsidal motion.Öğe The connection between the pulsational and orbital periods for eclipsing binary systems(Oxford Univ Press, 2006) Soydugan, E; Ibanoglu, C; Soydugan, F; Akan, MC; Demircan, OConsidering a sample of 20 eclipsing binary systems with delta Scuti type primaries, we discovered that there is a possible relation among the pulsation periods of the primaries and the orbital periods of the systems. According to this empirical relation, the longer the orbital period of a binary, the longer the pulsation period of its pulsating primary. Among the sample, the masses of the secondaries and the separations between the components are known for eight systems for which a log P-puls versus log F (the gravitational pull exerted per gram of the matter on the surface of the primaries by the secondaries) diagram also verifies such an interrelation between the periods. So, as the gravitational force applied by the secondary component onto the pulsating primary increases, its pulsation period decreases. The detailed physics underlying this empirical relation between the periods needs further confirmation, especially theoretically. However, one must also consider the fact that the present sample does not contain a sufficiently large sample of longer period (P > 5 d) binaries.
