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Öğe A binary star with a ? Scuti component(Astronomical Soc Pacific, 2007) Soydugan, Esin; Soydugan, FarukNew photometric observations of the Algol type binary system RZ Cassiopeiae were obtained in the B and V filters. The new light curves of the system were analyzed using the Wilson-Devinney code. As expected, the light curves of the system exhibit short-period oscillations due to pulsation of the primary component. The computed light curves have been subtracted from the observed ones to obtain the residual light curves. The frequency analysis was performed on the residual light curves using a computer package called PERIOD 04 (Lenz & Breger 2005). As a result of this analysis, we found that the primary component of RZ Cas shows multi-periodic pulsations.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 Silent Revolution in Fundamental Astrophysics(Iop Publishing Ltd, 2022) Eker, Zeki; Soydugan, Faruk; Bakis, Volkan; Bilir, Selcuk; Steer, IanArbitrariness in the zeropoint of bolometric corrections is a paradigm that is nearly a century old and leads to two more paradigms. Bolometric corrections must always be negative, and the bolometric magnitude of a star ought to be brighter than its V magnitude. Both were considered valid before the IAU 2015 General Assembly Resolution B2, a revolutionary document that supersedes all three aforementioned paradigms. The purpose of this article is to initiate new insight into and a new understanding of the fundamental astrophysics and present new capabilities to obtain standard and more accurate stellar luminosities and gain more from accurate observations in the era after Gaia. The accuracy gained will aid in advancing stellar structure and evolution theories and also Galactic and extragalactic research, observational cosmology, and searches for dark matter and dark energy.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 A spectroscopic survey of algol-type binary S Equ(Astronomical Soc Pacific, 2007) Soydugan, Faruk; Soydugan, Esin; Frasca, A.This study presents the results of the medium-resolution optical spectra of S Equ obtained with the echelle spectrograph of the Catania Astro-physical Observatory. In this work, new radial velocity curves for the components of the system with a precision better than in previous works are obtained using the cross-correlation technique. We have determined the absolute parameters of S Equ combining the orbit and light curve solutions. The preliminary results of the Ha line analysis indicate an extra emission and absorption as a likely result of a mass-transfer process and chromospheric activity of the cooler component.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 Analyses of Some Exoplanets' Transits and Transit Timing Variations(Amer Inst Physics, 2017) Puskullu, Caglar; Soydugan, FarukWe present solutions of the transit light curves and transit timing variations (TTVs) analyses of the exoplanets HAT-P-5b, HAT-P-9b and HAT-P-25b. Transit light curves were collected at canakkale Onsekiz Mart University Observatory and TUBITAK National Observatory. The models were produced by WINFITTER program and stellar, planetary and orbital properties were obtained and discussed. We gave new transit times and generated TTVs with them by appending additional data based on Exoplanet Transit Database (ETD). Significant signals at the TTVs were also investigated.Öğe Analysis of Exoplanet Light Curves(Astronomical Soc Pacific, 2015) Erdem, A.; Budding, E.; Rhodes, M. D.; Puskullu, Q.; Soydugan, Faruk; Soydugan, Esin; Tuysuz, M.We have applied the close binary system analysis package WINFITTER to a variety of exoplanet transiting light curves taken both from the NASA Exoplanet Archive and our own groundbased observations. WINFITTER has parameter options for a realistic physical model, including gravity brightening and structural parameters derived from Kopal's applications of the relevant Radau equation, and it includes appropriate tests for determinacy and adequacy of its best fitting parameter sets. We discuss a number of issues related to empirical checking of models for stellar limb darkening, surface maculation, Doppler beaming, microvariability, and transit time variation (TTV) effects. The Radau coefficients used in the light curve modeling, in principle, allow structural models of the component stars to be tested.Öğe Analysis of ground-based observations of some exoplanets(Canadian Science Publishing, Nrc Research Press, 2018) Puskullu, Caglar; Soydugan, FarukWe present analyses of the transit light curves and transit time measurements of the exoplanets HAT-P-3b, HD 189733b, and WASP-43b. Transit light curves were collected at Canakkale Onsekiz Mart University Observatory and TUBITAK National Observatory. The models were produced by WINFITTER code and stellar, planetary, and orbital properties were obtained and discussed. We searched for significant signals at the O-C diagrams generated with our transit times and additional data based on Exoplanet Transit Database.Öğe Analysis of light curve and orbital period of contact binary NO Vul(2021) Yıldırım, Muhammed Faruk; Soydugan, FarukIn this study, we investigated light curve analysis of contact binary system NO Vul. Also, we investigated orbital period variations of contact binaries NO Vul based on all published minima times and also those obtained from our own observations. Photometric observations are obtained from the ASAS public archive. Physical parameters of the system are derived using the modeling code by Wilson and Dewinney’s (WD). Photometric results indicate that NO Vul is q = 0.72(2) and about f =%19 respectively and the derived orbital inclination i =77(1).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 CN Andromedae: a shallow contact binary with a possible tertiary component(Natl Astronomical Observatories, Chin Acad Sciences, 2019) Yildirim, Muhammed Faruk; Alicavus, Fahri; Soydugan, FarukIn this study, new photometric observations of shallow contact binary CN Andromedae (CN And) were performed and multi-color (BV R) CCD light curves (LCs) were obtained. Simultaneous analysis of new LCs and published radial velocity (RV) data reveals that the system is an early contact binary in which both components have recently filled their inner Roche lobes. Asymmetric LCs were modeled by a dark spot on the primary component and a hot spot on the secondary component that probably resulted from magnetic activity and mass transfer, respectively. Modeling of LCs and RV data allows us to estimate the following absolute parameters: M-1= 1.40 +/- 0.02 M-circle dot, M-2 = 0.55 +/- 0.01 M-circle dot, R-1 = 1.45 +/- 0.02 R-circle dot and R-2 = 0.94 +/- 0.02 R-circle dot. A decreasing orbital period with a rate of dP/dt = -1.5 x 10(-7) d yr(-1) can be seen as evidence that the system is evolving into a contact binary with higher contact degree. Cyclic oscillation of the O - C data was interpreted by the Applegate mechanism and light-time effect due to an unseen component around the close binary system. The hypothetical third component is probably a fully convective red dwarf star with a minimal mass of 0.1 M-circle dot. CN And is at the early phase of the contact stage of its evolution and is an interesting example for studying the formation and evolution of close binaries.Öğe Cool Active Binaries Recently Studied in the CAAM Stellar Program(Astronomical Soc Pacific, 2010) Cicek, C.; Erdem, A.; Soydugan, Faruk; Dogru, D.; Ozkardes, B.; Erkan, N.; Budding, E.We summarize recent work on cool active stars in our programme. We carried out photometry at the canakkale Onsekiz Mart University (COMU) observatory, and high-resolution spectroscopy at Mt John University Observatory, as well as collecting data from other facilties. A combination of analysis methods, including our information limit optimization technique (ILOT) with physically realistic fitting functions, as well as other public-domain software packages, have been used to find reliable parameters. Stars in our recent programme include V1430 Aql, VI 034 Her, V340 Gem, SAO 62042, FI Cnc, V2075 Cyg, FG UMa and BM CVn. Light variations, sometimes over numerous consecutive cycles, were analysed. For AB Dor and CF Tuc, we compared broadband (B and V) maculation effects with emission features in the Ca II K and H-alpha lines. Broadband light curves typically show one or two outstanding maculae. These appear correlated with the main chromospheric activity sites ('faculae'), that occur at similar latitudes and with comparable size to the photometric umbrae, but sometimes with significant displacements in longitude. The possibility of large-scale bipolar surface structure is considered, keeping in mind solar analogies. Such optical work forms part of broader multiwavelength studies, involving X-ray and microwave observations, also mentioned.Öğe Delta scuti bileşenli örten çift sistemlerin zonklama özelliklerinin belirlenmesi(2011) Soydugan, Esin; Soydugan, Faruk; Bilir, Selçuk; Bakış, Volkan; Demircan, Osman[Abstract Not Available]Öğe Discovery of ? scuti type oscillations in two algol-type binaries: DY Aqr and Bg Peg(Hungarian Academy of Sciences (Konkoly Observatory), 2009) Soydugan, Esin; Soydugan, Faruk; Enyuz, T.; Puskullu, Q.; Tuysuz, M.; Bakis, V.; Bilir, S.[No abstract available]Öğe Discovery of {delta} Scuti type oscillations in two Algol-type binaries: DY Aqr and BG Peg(2009) Soydugan, Esin; Soydugan, Faruk; Senyüz, T.; Püsküllü, Ç.; Tüysüz, M.; Bakis, V.; Bilir, S.[No abstract available]Öğe Effective Temperatures of Selected Main-Sequence Stars with the Most Accurate Parameters(Astronomical Soc Pacific, 2015) Soydugan, Faruk; Eker, Z.; Soydugan, Esin; Bilir, S.; Gokce, E. Y.; Steer, I.; Tuysuz, M.In this study we investigate the distributions of the properties of detached double-lined binaries (DBs) in the mass luminosity, mass radius, and mass-effective temperature diagrams. We have improved the classical mass luminosity relation based on the database of DBs by Eker et al. (2014a). Based on the accurate observational data available to us we propose a method for improving the effective temperatures of eclipsing binaries with accurate mass and radius determinations.
