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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 comprehensive photometric study of the Algol-type eclipsing binary: BG Pegasi(Elsevier Science Bv, 2011) Soydugan, Esin; Soydugan, Faruk; Senyuz, T.; Puskullu, C.; Demircan, O.This study presents new photometric observations of classical Algol type binary BC Peg with a delta Scuti component The light curve modeling was provided with the physical parameters of the component stars in the BC Peg system for the first time After modeling light curves in B and V filters, the eclipse and proximity effects were removed from the light curve to analyze intrinsic variations caused by the hotter component of the system Frequency analysis of the residuals light represents the multi-mode pulsation of the more massive component of the BC Peg system at periods of 0.039 and 0 047 clays Two frequencies could be associated with non-radial (l = 2) modes The total amplitude of the pulsational variability in the V light curve was found to be about 0 045 mag The long-term orbital period variation of the system was also investigated for the first time The O-C analysis indicates periodic variation superimposed on a downward parabola The secular period variation means that the orbital period of the system is decreasing at a rate of -5 5 seconds per century, probably due to the magnetic activity of the cooler component. The tilted sinusoidal O-C variation may be caused by the gravitational effect of an unseen component around the system (C) 2010 Elsevier B V All rights reservedÖğe A new catalogue of eclipsing binary stars with eccentric orbits(Blackwell Publishing, 2007) Bulut, I.; Demircan, O.A new catalogue of eclipsing binary stars with eccentric orbits is presented. The catalogue lists the physical parameters (including apsidal motion parameters) of 124 eclipsing binaries with eccentric orbits. In addition, the catalogue also contains a list of 150 candidate systems, about which not much is known at present.Öğe A spectroscopic study of some Algol systems(2005) Soydugan, Faruk; Frasca, A.; Catalano, S.; Ibano?lu, C.; Demircan, O.; Soydugan, EsinWe present and discuss here new high-resolution (R? 22000) optical spectra of three Algol binaries, namely KO Aql, S Equ and AT Peg, obtained with the echelle spectrograph of Catania Astrophysical Observatory. In this work, we obtained new radial velocity curves for the hotter primary components with a much better precision than the previous data in the literature, mainly coming from old plate spectra. Thanks to the cross-correlation procedure, we were able to obtain, for the first time to our knowledge, radial velocities also for the cool secondary components of KO Aql and S Equ. We have also measured, with a rather good accuracy (2-4 km/s), the rotational velocity of the hotter components of these three systems and found that, with the exception of AT Peg, the primary stars are rotating faster than the synchronization velocity, consistently with a mass transfer scenario. In addition, preliminary results on the mass-transfer effects displayed by the H? and H? extra-absorption/emission components are presented.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 Absolute dimensions and apsidal motion of the eccentric binary PT Velorum(Blackwell Publishing, 2008) Bakis, V.; Bakis, H.; Demircan, O.; Eker, Z.High-resolution (lambda/d lambda similar to 41 000) echelle spectra of the eccentric binary system PT Vel were analysed. Precise spectroscopic orbital elements of the system were obtained by means of cross-correlation technique. According to the solution of radial velocities with Hipparcos and All Sky Automated Survey-3 (ASAS-3) light curves, PT Vel consists of two main-sequence stars with masses M-1 = 2.198 +/- 0.016 M-circle dot, M-2 = 1.626 +/- 0.009 M-circle dot, radii R-1 = 2.094 +/- 0.020 R-circle dot, R-2 = 1.559 +/- 0.020 R-circle dot and temperatures T-eff1 = 9250 +/- 150 K, T-eff2 = 7650 +/- 200 K separated from each other by A = 9.74 +/- 0.02 R-circle dot in an orbit inclined 88.2 degrees +/- 0.5. The projected rotational velocities of component stars were found to be (v sin i)(1) = 63 +/- 2 and (v sin i)(2) = 40 +/- 3 km s(-1) from the comparison of observed spectra with synthetic spectra which were calculated using model atmospheres. Our measurements of the projected rotational velocities indicate that both stars rotate synchronously. Analysis of longitude of periastron values obtained from light-curve analysis from different photometric sets of this moderately eccentric system (e = 0.127 +/- 0.006) has revealed a significant motion of the line of apsides of (w) over dot = 0.0097 +/- 0 degrees.0004 cycle(-1) corresponding to an apsidal motion period of U = 182.2 +/- 8.4 yr. The contribution from general relativity effects is moderate (similar to 9 per cent). A comparison with predictions from interior structure models shows the real stars to be more concentrated in mass than expected. Comparison of absolute dimensions with theoretical isochrones yielded an age of the system of 400 +/- 40 Myr.Öğe Absolute dimensions and apsidal motion of the eccentric binary V731 Cephei(Oxford Univ Press, 2008) Bakis, V.; Zejda, M.; Bulut, I.; Wolf, M.; Bilir, S.; Bakis, H.; Demircan, O.A detailed analysis of new and existing photometric, spectroscopic and spatial distribution data of the eccentric binary V731 Cep was performed. Spectroscopic orbital elements of the system were obtained by means of cross-correlation technique. According to the solution of radial velocities with UBVRc and I-c light curves, V731 Cep consists of two main-sequence stars with masses M-1 = 2.577 (0.098) M-circle dot, M-2 = 2.017 (0.084) M-circle dot, radii R-1 = 1.823 (0.030) R-circle dot, R-2 = 1.717 (0.025) R-circle dot and temperatures T-eff1 = 10700 (200) K, T-eff2 = 9265 (220) K separated from each other by a = 23.27 (0.29) R-circle dot in an orbit with inclination of 88 degrees.70 (0.03). Analysis of the O-C residuals yielded a rather long apsidal motion period of U = 10000 (2500) yr compared to the observational history of the system. The relativistic contribution to the observed rates of apsidal motion for V731 Cep is significant (76 per cent). The combination of the absolute dimensions and the apsidal motion properties of the system yielded consistent observed internal structure parameter (log (k) over bar (2,obs) = -2.36) compared to the theory ( log (k) over bar (2,theo) = -2.32). Evolutionary investigation of the binary by two methods (Bayesian and evolutionary tracks) shows that the system is t = 133(26) Myr old and has a metallicity of [M/H] = -0.04(0.02) dex. The similarities in the spatial distribution and evolutionary properties of V731 Cep with the nearby (rho similar to 3 degrees.9) open cluster NGC 7762 suggest that V731 Cep could have been evaporated from NGC 7762.Öğe Absolute parameters of young stars - II. V831 Centauri(Oxford Univ Press, 2010) Budding, E.; Erdem, A.; Inlek, G.; Demircan, O.Literature photometry and new high-resolution spectroscopy of V831 Cen are presented and analysed. Light and radial velocity curve fittings confirm the central pair of this young multiple system to be close to contact. Absolute parameters are found as follows: M-1 = 4.08 +/- 0.07 M-circle dot, M-2 = 3.35 +/- 0.06 M-circle dot, R-1 = 2.38 +/- 0.03 R-circle dot, R-2 = 2.25 +/- 0.03 R-circle dot, T-1 = 13 000 +/- 300 K, T-2 = 11 800 +/- 300 K; distance of 110 +/- 10 pc and age of similar to 20 +/- 5 Myr. Detailed examination of the spectrograms indicates the third component (V831 Cen B) to be an Ap star. The orbit of the third star about the close binary is analysed using historic astrometric measurements. This allows an estimate of the third star's mass to be about 2.5 M-circle dot, but this is sensitive to the adopted distance and inclination values. It is, however, confirmed by the measured radial velocity of the third star. To some extent, such analysis can also be applied to the fourth star (V831 Cen C). The derived properties can be checked against the system's membership of the Scorpius-Centaurus OB2 association.Öğe Absolute parameters of young stars: HX Velorum(Oxford Univ Press, 2019) Blackford, M. G.; Erdem, A.; Surgit, D.; Ozkardes, B.; Budding, E.; Butland, R.; Demircan, O.We present combined photometric and spectroscopic analyses of the southern multiple star HX Vel. High-resolution spectra of this system were taken at the University of Canterbury Mt. John Observatory in the years 2009-2015. Absolute parameters for HX Vel tend to confirm its young and near-main-sequence nature. We specify the main adopted parameters of the (non-eclipsing) close binary as follows: M-1 = 8.5 +/- 1.7, M-2 = 5.4 +/- 1.2, R-1 = 5.0 +/- 0.3, R-2 = 3.1 +/- 0.2, (circle dot); T-1 25 000 +/- 1300, T-2 20 000 +/- 2500 (K); systemic M-V -4.2 +/- 0.2. These parameters are sensitive to the low inclination, where we find a small disparity between the photometrically optimal 28 +/- 2 degrees and an adopted value of 26 degrees that gives better consistency with main-sequence stellar modelling. The relationship of HX Vel to the galactic cluster IC 2395 and OB association Vela OB1C is also considered, in the context of photometric parallaxes found for HX Vel and other cluster members.Öğe Absolute parameters of young stars: V454 Carinae(Oxford Univ Press, 2019) Butland, R. J.; Erdem, A.; Ozkardes, B.; Blackford, M. G.; Surgit, D.; Budding, E.; Demircan, O.We present combined photometric and spectroscopic analyses of the multiple star V454 Carinae. High-resolution spectra of the system were taken at the University of Canterbury Mt. John Observatory during the years 2008-18. These have been processed using generic and purpose-built software. New digital single lens reflex photometry of the system has also been collected and similarly analysed. Absolute parameters for the three main stars confirm V454 Car's young and near-Main-Sequence nature. We find: M-1 = 4.6 +/- 0.4, M-2 = 4.4 +/- 0.4, M-3 = 4.5 +/- 0.5, R-1 = 2.83 +/- 0.18, R-2 = 2.74 +/- 0.16, R-3 = 2.78 +/- 0.16 (circle dot); T-1 similar to 17 500, T-2 similar to 15 500, T-3 similar to 15 000 (K), age similar to 30 Myr, photometric distance similar to 500 (pc). The major component V454 Car A is the close binary identified by the HIPPARCOS satellite. This binary and component B appear to be in eccentric orbits about a common centre of gravity with a period of similar to 1900 d. Analysis of the radial velocity curves suggests that the mass of component B is greater than that of its visible member. Measured radial velocities of this visible star show irregularities with a time-scale of about a week. The galactic location, proper motions, and age of V454 Car support the runaway nature proposed by others, and the combined results are consistent with a dynamical ejection scenario from the Vela region of Gould's Belt relatively soon after the stars' formation.Öğe Active binary R Arae revisited: Bringing the secondary component to light and physical modelling of the circumstellar material(Oxford Univ Press, 2016) Bakis, H.; Bakis, V.; Eker, Z.; Demircan, O.The spectral lines of the secondary component of the active binary system R Ara were uncovered for the first time, which allowed directly to determine the parameters of the spectroscopic orbit. The mass ratio of the system is updated to a new observational value of M-2/M-1 = 0.305 +/- 0.005 which is similar to 20 per cent smaller than the literature value (M-2/M-1 = 0.39). Modelling the reconstructed component spectra yielded the equatorial rotational velocities of the components as nu(rot1) = 202 km s(-1) and nu(rot2) = 73 km s(-1) indicating a very fast rotation (similar to 5 times faster than the synchronous rotation velocity) for the primary and synchronous rotation for the secondary component. The circumstellar material in the system was investigated using the Hipparcossatellite data and the high-resolution (R similar to 41 000) spectral data. According to our model, there is always material transferring from the secondary component on to the primary causing a hot region on its surface. The structural difference between the spectra taken at the same orbital phase but at different epochs proved that the density and the velocity of the transferring material are variable. There are three main trends in the light curve and spectral line variations suggesting the activity cycles for the system, namely quiescent, moderate and, active cycles. It was estimated that the circumstellar material around could be extended to large distances up to 40 R-circle dot from the system.Öğe Age Dependent Angular Momentum, Orbital Period and Total Mass of Detached Binaries(Cambridge Univ Press, 2012) Demircan, O.; Tuysuz, M.; Soydugan, Faruk; Bilir, S.The orbital angular momenta OAM (J) of detached binaries (including both cool and hot binaries) were estimated and nine subgroups were formed according to their OAM (3) distribution. The mean kinematical ages of all subgroups have been estimated by using their space velocity distributions and, thus, the age dependent variations of the mean OAM (3), orbital period (13), and total mass (M) of all subgroups were investigated. It was discovered that: i) The orbital period of detached binaries with radiative components decrease very slowly during the main sequence (MS) evolution. It is interesting that the large amount of mass loss is almost balanced by the OAM loss, and not much change in the orbital periods is observed. ii) The nuclear evolution of radiative components beyond the MS initiates the increase of the periods until the components have convective upper layers, i.e. until they become later than F5 IV, and the system becomes a cool binary with sub-giant or giant components. iii) The large co-rotating distance of the magnetically-driven wind in cool binaries (CAB) carries out a large amount of OAM and then the periods of such binaries decrease significantly, and the orbits shrink until another effect such as mass transfer dominates the period changes.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 Analysis of ? Librae including Hipparcos astrometry(Blackwell Publishing, 2006) Bakis, V.; Budding, E.; Erdem, A.; Bakis, H.; Demircan, O.; Hadrava, P.New spectroscopy of the classical Algol system delta Lib, combined with high-quality optical and infrared photometry, provides the basis for a good understanding of the close binary system's main parameters. Detailed analysis of the photometry reveals the significant role of a third light source, pointing to the existence of a companion to the eclipsing system of mass similar to 1 M-circle dot. We review the methodology of applying high-accuracy positional information, available from the Hipparcos Intermediate Astrometric Data archive, to stars that may have such companions. Analysis of the astrometry of delta Lib also points to a third star similar to the one already identified by Worek from radial-velocity data, although with slightly revised parameters. O-C data do not contradict this, but their general precision (while confirming the close pair's Algol status) fails to allow a decision on the third orbit parameters: Worek's or revised ones. Taking the photometry, spectroscopy and astrometry together, however, the existence of a third star of comparable mass to the Sun, as a relatively close companion to the eclipsing binary (similar to 4 au), is confirmed.Öğe Analysis of the exoplanet containing system Kepler-91(Springer, 2016) Budding, E.; Puskullu, C.; Rhodes, M. D.; Demircan, O.; Erdem, A.We have applied the graphical user interfaced close binary system analysis program WINFITTER to an intensive study of Kepler-91 using all the available photometry from the NASA Exoplanet Archive (NEA) at the Caltech website: http://exoplanetarchive.ipac.caltech.edu. Our fitting function for the tidal distortion derives from the relevant Radau equation and includes terms up to the fifth power of the fractional radius. This results in a systematic improvement in the mass ratio estimation over that of Lillo-Box et al. (Astron. Astrophys. 562:A109, 2014a) and our derived value for the mass ratio is in close agreement with that inferred from recent high-resolution spectroscopic data. It is clear that the data analysis in terms of simply an eclipsing binary system is compromised by the presence of significant other causes of light variation, in particular non-radial pulsations. We apply a low-frequency filtering procedure to separate out some of this additional light variation. Whilst the derived eccentricity appears then reduced, an eccentric effect remains in the light curve. We consider how this may be maintained in spite of likely frictional effects operating over a long time. There are also indications that could be associated with Trojan or other period-resonant mass concentrations. Suggestions of a possible secular period variation are briefly discussed.Öğe Collaborative Studies of Southern Close Binary Systems(Astronomical Soc Pacific, 2015) Budding, E.; Blackford, M.; Butland, R.; Demircan, O.; Erdem, A.; Idaczyk, R.; Ozkardes, B.We present a few items from our southern eclipsing binary program, underway in recent years and involving observations at the Mt. John University Observatory and elsewhere in Australasia. Reduction and analysis have also been carried out at COMU (Turkey). Derived parameters allow interesting comparisons with other recent findings on binary stars, observational and theoretical.Öğe Discovery of new variable stars at the Canakkale Onsekiz Mart University Observatory(Astronomical Soc Pacific, 2007) Bakis, V.; Bakis, H.; Demircan, O.; Budding, E.; Erdem, A.; Cicek, C.We present the light curves of five variable stars discovered at the Canakkale Onsekiz Mart University Observatory. From the light curve shapes of the variables we see that GSC 4288 0186 and GSC 4019 3345 are detached, USNO 1500-00409928 is a W UMa-type eclipsing binary, while the others seem to be intrinsic variable stars. By using a 30-cm telescope equipped with an ST237 CCD camera dedicated for times of minima observations, we plan to perform systematic observations to discover new variable stars with the help of automatic data reduction techniques in the future.Öğe Dynamical evolution of active detached binaries on the log Jo-log M diagram and contact binary formation(Blackwell Publishing, 2006) Eker, Z.; Demircan, O.; Bilir, S.; Karatas, Y.Orbital angular momentum (OAM, J(o)), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of logJ(o)-IogP, logM-logP and logJ(o)-IogM were fortned from 119 CAB and 102 W UMa stars. The log J(o)-Iog M diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the log J(o)-Iog M diagram. Since the orbital size (a) and period (P) of binaries are determined by their current J(o), M and mass ratio, q, the rates of OAM loss (d log J(o)/dt) and mass loss (d log M/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a contact system if its own dynamical evolution enables it to pass the contact border on the log J(o)-log M diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of J(o) and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6 Gyr, respectively.Öğe Evidences on secular dynamical evolution of detached active binary orbits and contact binary formation(Astronomical Soc Pacific, 2007) Eker, Z.; Demircan, O.; Bilir, S.; Karatas, Y.Evidence of secular dynamical evolution for detached active binary orbits are presented. First order decreasing rates of orbital angular momentum (OAM), systemic mass (M = M-1 + M-2) and orbital period of detached active binaries have been determined a J/J = 3.48 x 10(-10)yr(-1),M/M = 1.30 x 10(10)yr(-1) and P/P 3.96 x 10(-10)yr(-1) from the kinematical ages of 62 field detached systems. The ratio of d log J/ d log M = 2.68 implies that either there are mechanisms which amplify AM loss delta = 2.68 times with respect to isotropic AM loss of hypothetical isotropic winds or there exist external causes contributing AM loss in order to produce this mean rate of decrease for orbital periods. Various decreasing rates of OAM (d log J /dt) and systemic mass (d log M /dt) determine various speeds of dynamical evolutions towards a contact configuration. According to average dynamical evolution with delta = 2.68, the fraction of 10, 22 and 39 per cent of current detached sample is expected to be contact system within 2, 4 and 6 Gyr respectively.Öğe First ground-based photometry and light-curve analysis of the eccentric eclipsing binary V744 Cas(Wiley-V C H Verlag Gmbh, 2006) Bulut, I.; Cicek, C.; Erdem, A.; Bakis, V.; Demircan, O.; Degirmenci, O. L.The first ground-based BVR photometric observations of the recently discovered eclipsing binary V744 Cas are presented. From these measurements, timings for two primary and one secondary minima have been calculated. The light curves of the system were analyzed by using the Wilson-Devinney program. The analysis shows that the system is detached with two similar components of spectral type A2V, and the orbit is eccentric (e = 0.0662 +/- 0.0005). The longitude of the periastron (w) was found significantly different for two different light curves (ours and that of Hipparcos), which is strongly suggestive of an apsidal motion with a period of about 425 +/- 68 yr. This makes V744 Cas an important candidate for studies of apsidal motions. The first estimate of the absolute dimensions place the system close to the terminal age of the main sequence (TAMS) in the HR diagram. The distance from the spectroscopic parallax (d = 740 +/- 10 pc) was found to be slightly larger than the Hipparcos distance of d = 610 +/- 400 pc. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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