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Öğe A catalogue of close binaries located in the ? Scuti region of the Cepheid instability strip(Oxford Univ Press, 2006) Soydugan, Esin; Soydugan, Faruk; Demircan, O.; Ibanoglu, C.A catalogue of close eclipsing binary systems (detached and semidetached) with at least one of the components located in the delta Scuti region of the Cepheid instability strip is presented. The positions of the stars in the instability strip are determined by their accurate temperatures and luminosities. Observationally detected binaries (20 semidetached, four detached and one unclassified) with oscillating components were included in the catalogue as a separate table. The primaries of the oscillating Algols tend to be located near the blue edge of the instability strip. Using reliable luminosities and temperatures determined by recent photometric and spectroscopic studies, we have found that at least one or two components of 71 detached and 90 semidetached systems are located in the delta Scuti region of the Cepheid instability strip. In addition, 36 detached or semidetached systems discovered by the Hipparcos satellite were also given as a separate list. One of their components is seen in the delta Scuti region, according to their spectral type or B - V colours. They are potential candidate binaries with the delta Scuti-type pulsating components which need further photometric and spectroscopic studies in better precision. This catalogue covers information and literature references for 25 known and 197 candidate binaries with pulsating components.Öğe A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer(Blackwell Publishing, 2007) Soydugan, Faruk; Frasca, A.; Soydugan, Esin; Catalano, S.; Demircan, O.; Ibanoglu, C.We present and analyse high-resolution optical spectra of two Algol binaries, namely S Equ and KO Aql, obtained with the echelle spectrograph at Catania Astrophysical Observatory. New accurate radial velocities (RVs) for the hotter primary components are obtained. Thanks to the cross-correlation procedure, we were able to measure, for the first time to our knowledge, RVs also for the cool secondary components of S Equ and KO Aql. By combining the parameters obtained from the solution of the RV curves with those obtained from the light-curve analysis, reliable absolute parameters of the systems have been derived. The rotational velocity of the hotter components of S Equ and KO Aql has been measured and it is found that the gainers of both systems rotate about 30 per cent faster than synchronously. This is likely due to mass transfer across the Lagrangian L-1 point from the cooler to the hotter component. The lower luminosity of the mass-gaining components of these systems compared to normal main-sequence stars of the same mass can also be an effect of the mass transfer. The H alpha profiles were analysed with the 'synthesis and subtraction' technique and reveal clear evidence of mass transfer and accretion structures. In both systems, especially before the primary eclipses and afterwards, we clearly observed extra absorption lines. From the integrated absorption and the RV variations of these features, we found that the mass accretion is very dense around the impact region of the hotter components. A double-peaked emission in the spectra of S Equ was seen outside the eclipses. One of these peaks is likely originated in a region between the centre of mass and the cooler component, which is occupied by the flowing matter. Furthermore, the H alpha difference spectra of S Equ and KO Aql also display emission features, which should be arising from the magnetic activity of the cooler components.Öğe An algol type binary with a ? Scuti component(Wiley-V C H Verlag Gmbh, 2006) Soydugan, Esin; Soydugan, Faruk; Ibanoglu, C.; Frasca, A.; Demircan, O.; Akan, M. C.We present new BV photometry and spectroscopic observations of RZ Cassiopeiae. The light and radial velocity curves were formed by the new observations which have been analyzed simultaneously by using the Wilson-Dewinney code. The non-synchronous rotational velocity v(1) sin i = 76 +/- 6 km s(-1), deduced for the primary component from the new spectroscopic observations, was also incorporated in the analysis. A time-series analysis of the residual light curves revealed the multi-periodic pulsations of the primary component of RZ Cas. The main peak in the frequency spectrum was observed at about 64.197 c d(-1) in both B and V bands. The pulsational constant was calculated to be 0.0116 days. This value corresponds to high overtones (n similar to 6) of non-radial mode oscillations. We find significant changes in the pulsational amplitude of the primary component from year to year. The peak-to-peak pulsational amplitude of the main frequency displays a decrease from 0.(m)-013 in 2000 to 0.(m)002 in 2001 and thereafter we have found an increase again in the amplitude to 0.(m)01 in the year 2002. We propose the mass transfer from the cool secondary to the pulsating primary as a possible explanation for such remarkable changes in the pulsational behavior of the primary component. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Öğe Angular momentum evolution of Algol binaries(Oxford Univ Press, 2006) Ibanoglu, C.; Soydugan, Faruk; Soydugan, Esin; Dervisoglu, A.We have compiled the well-determined absolute parameters of Algol-type binaries. The lists contain the parameters of 74 detached and 61 semidetached close binaries. The double-lined eclipsing binaries provide not only the most accurate determinations of stellar mass, radius and temperatures but also distance-independent luminosity for each of their individual components. The distributions of the primary and secondary masses of detached binaries (DBs) are similar, whilst the secondary masses of the semidetached binaries (SDBs) are mostly smaller than 2 M-circle dot with a peak in the M-2-bin (0.21-1.0). The components of the DBs are almost all located in the main-sequence band. On the contrary, the secondary components of the SDBs have larger radii and luminosity with respect to the same mass and the same effective temperature of main-sequence counterparts. They occupy a region of the Hertzsprung-Russell diagram between terminal-age main sequence and giants. Moreover, the total angular momenta and specific angular momenta are larger for the SDBs of orbital periods with P > 5 d than those of the shorter period ones. The specific angular momenta of SDBs with periods longer than 5 d are 65 per cent greater than that of the short period group with the same mass. The DBs and the SDBs with orbital periods longer and shorter than 5 d are separated into three groups in the J/M-5/3 - q diagram. The SDBs with mass ratios greater than 0.3 and P > 5 d have almost the same angular momentum to those of DBs. However, the SDBs with short periods have the smallest angular momentum even though they have the same mass ratios. This result reveals that angular momentum loss (AML) considerably affects the evolution of close binary systems. Recently, Chen, Li & Qian suggested that, in addition to magnetic braking, a circumbinary disc may play an important role in AML from Algol-type binaries. Their calculations indicated that the evolution of Algol-type binaries can be significantly affected by the circumbinary disc. Our results show that the evolution of close binaries begins as a DB and losing angular momentum, first via stellar wind and then magnetic braking plus circumbinary disc the period is shortened and orbit shrinks. Thereafter, the evolution of the system is accelerated and mass transfer rates are enhanced which result in a smaller mass ratios.Öğe Long-term orbital period behaviors of the neglected Algol type binaries: CC Herculis and XZ Aquilae(Wiley-V C H Verlag Gmbh, 2006) Soydugan, Faruk; Soydugan, Esin; Ibanoglu, C.; Demircan, O.Orbital period variations of two neglected Algol type binaries, CC Her and XZ Aql, are studied based on all available times of minima. In the case of CC Her, it is found that the O-C curve displays a tilted sinusoidal variation with an eccentricity of 0.54 +/- 0.03 and a period of 52.4 +/- 0.4 yr, which can be explained by the light-time effect due to the presence of an unseen component. The course of the orbital period change in XZ Aql appears less reliable but its O-C curve can be represented by a periodic variation with a period of 36.7 +/- 0.6 yr superimposed on an upward parabola. The parabolic variation indicates a secular period increase with a rate of dP/dt = 7.1 s per century. The corresponding conservative mass transfer from less massive component to the more massive one is about 3.26 x 10(-7) M-circle dot yr(-1). It is interesting to see that the O-C variation of CC Her displays no evidence (as upward parabola) on the mass transfer characteristic for Algols. The periodic change of the orbital period of XZ Aql, like CC Her, may be caused by the presence of the third-body. The lower limits of the masses of the hypothetical unseen components for CC Her and XZ Aql are found to be 2.69 M-circle dot and 0.47 M-circle dot, respectively. The third body of CC Her should be detectable not only spectroscopically but also photoelectrically, if it exists. (c) 2006 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim.Öğe Preliminary results on the fundamental parameters of the eclipsing binary V398 Lacertae*(Wiley-V C H Verlag Gmbh, 2007) Cakirli, Oe.; Frasca, A.; Ibanoglu, C.; Soydugan, Faruk; Degirmenci, Oe.The Hipparcos Space Astrometry Mission photometric observations of V398 Lac, led to the discovery of its variability, allowing to classify it as an eclipsing binary with an orbital period of about 5.4 days. This prompted us to acquire high-resolution echelle spectra with the aim of performing accurate radial velocity measurements and to determine the main physical parameters of the system's components. We present, for the first time, a double-lined radial velocity curve and determine the orbital and physical parameters of the two components, that can be classified both as late B-type stars. In particular, we obtained an orbital inclination i similar to 85 degrees. With this value of the inclination, we deduced masses M-1 = 3.83 +/- 0.35 M-circle dot and M-2 = 3.29 +/- 0.32 M-circle dot, and radii R-1 = 4.89 +/- 0.18 R-circle dot and R-2 = 2.45 +/- 0.11 R-circle dot for the more massive and less massive components, respectively. Both components are well inside their own Roche lobes. The mass ratio is M-2/M-1, similar to 0.86. We derived also the projected rotational velocities as v(1) sin i = 79 +/- 2 km s(-1) and v(2) Sin i = 19 +/- 2 km s(-1). Our measurements indicate that the rotation of the primary star is essentially pseudo-synchronized with the orbital velocity at the periastron, while the secondary appears to rotate very slowly and has not yet attained synchronization. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
