Astrofizik Araştırma Merkezi ve Ulupınar Gözlemevi Yayın Koleksiyonu

Bu koleksiyon için kalıcı URI

https://hdl.handle.net/20.500.12428/3697

Listeleniyor 1 - 20 / 25

δ Scuti-type pulsation in the hot component of the Algol-type binary system BG Peg
(Cambridge Univ Press, 2014) Şenyüz, Tunç; Soydugan, Esin
In this study, 23 Algol-type binary systems, which were selected as candidate binaries with pulsating components, were observed at the canakkale Onsekiz Mart University Observatory. One of these systems was BG Peg. Its hotter component shows delta Scuti-type light variations. Physical parameters of BG Peg were derived from modelling the V light curve using the Wilson-Devinney code. The frequency analysis shows that the pulsational component of the BG Peg system pulsates in two modes with periods of 0.039 and 0.047 d. Mode identification indicates that both modes are most likely non-radial l = 2 modes.
KIC 10486425: A Kepler eclipsing binary system with a pulsating component
(Cambridge Univ Press, 2014) Kahraman Aliçavuş, Filiz; Soydugan, Esin
We present frequency analysis of the Kepler light curve of KIC 10486425, an eclipsing binary system with a pulsating component. The parameters of the binary were obtained by modelling the light curve with the Wilson-Devinney program. The residuals from this modelling were subject to Fourier analysis which allowed us to detect 120 periodic terms characteristic for gamma Dor-type pulsations. The dominant frequency of these changes amounts to 1.3189 d(-1).
Kinematic Properties of Chromospheric Active Binary Stars
(Cambridge Univ Press, 2012) Tüysüz, Mehmet; Soydugan, Faruk; Bilir, S.; Demircan, Oya
The kinematic behaviour of 362 chromospherically active binary stars (CABs) in the solar neighbourhood were investigated. The Third CABs Catalog by Eker et al. (2008) was used as the main source. The spatial distribution and the components of the Galactic space velocities of the programme stars were determined. The effects of differential rotation and Local Standard of Rest (LSR) were corrected for all systems. Forty probable moving group (MG) members were determined by Eggen's criteria. The kinematic age of the young systems, which are probable members of MGs, was calculated as 0.79 (0.21) Gyr and the rest of 322 field stars were found to have a kinematic age of 4.38 (1.1) Gyr. Field CABs were separated into two sub-groups: dwarf systems, which were formed by main sequence (dwarf) stars, and evolved systems included at least one evolved (giant or sub-giant) component. The kinematic age of 134 dwarf systems was calculated as 4.69 (0.75) Gyr and 4.15 (1.29) Gyr for 188 evolved CABs.
Spectroscopic Study of the Early-Type Binary HX Vel A
(Cambridge Univ Press, 2012) Özkardeş, Burcu; Sürgit, Derya; Erdem, Ahmet; Budding, Edwin; Soydugan, Faruk; Demircan, Osman
This paper presents high resolution spectroscopy of the HX Vel (IDS 08390-4744 AB) multiple system. New spectroscopic observations of the system were made at Mt. John University Observatory in 2007 and 2008. Radial velocities of both components of HX Vel A were measured using gaussian fitting. The spectroscopic mass ratio of the close binary was determined as 0.599 +/- 0.052, according to a Keplerian orbital solution. The resulting orbital elements are a(1)sini=0.0098 +/- 0.0003 AU, a(2)sini=0.0164 +/- 0.0003 AU, M(1)sin(3)i=1.19 +/- 0.07 M-circle dot and M(2)sin(3)i=0.71 +/- 0.04 M-circle dot.
O-C Analysis of Selected 3-Body Systems
(Cambridge Univ Press, 2012) Ogloza, W.; Kreiner, J. M.; Stachowski, G.; Winiarski, M.; Zakrzewski, B.; Doğru, Serkan; Aliçavuş, Fahri; Demircan, Oya; Erdem, Ahmet
This paper presents the results of the analysis of (O-C) diagrams of four eclipsing variables. The diagrams are based on times of minima collected in the Cracow database, which contains times of minima found in the literature, from observations at Mt. Suhora and Ulupinar Observatories, or determined using publicly-available photometric surveys (NSVS, ASAS etc).
Photometric and Kinematic Studies of Open Clusters Ruprecht 1 and Ruprecht 171
(Wiley-V C H Verlag Gmbh, 2024) Çakmak, Hikmet; Yontan, Talar; Bilir, Selçuk; Banks, Timothy S.; Michel, Raul; Soydugan, Esin; Koç, Seliz
This study outlines a detailed investigation using CCD UBV and Gaia DR3 data sets of the two open clusters Ruprecht 1 (Rup-1) and Ruprecht 171 (Rup-171). Fundamental astrophysical parameters such as color excesses, photometric metallicities, ages, and isochrone distances were based on UBV-data analyses, whereas membership probability calculations, structural and astrophysical parameters, as well as the kinematic analyses were based on Gaia DR3-data. We identified 74 and 596 stars as the most probable cluster members with membership probabilities over 50% for Rup-1 and Rup-171, respectively. The color excesses E(B-V) were obtained as 0.166 +/- 0.022 and 0.301 +/- 0.027 mag for Rup-1 and Rup-171, respectively. Photometric metallicity analyses were performed by considering F-G type main-sequence member stars and found to be [Fe/H]=-0.09 +/- 0.16 and [Fe/H]=-0.20 +/- 0.20 dex for Rup-1 and Rup-171, respectively. Ages and distances were based on both UBV and Gaia-data analyses; according to isochrone-fitting these values were estimated to be t=580 +/- 60 Myr, d=1469 +/- 57 pc for Rup-1 and t=2700 +/- 200 Myr, d=1509 +/- 69 pc for Rup-171. The present-day mass function slope of Rup-1 was estimated as 1.26 +/- 0.32 and Rup-171 as 1.53 +/- 1.49. Galactic orbit integration analyses showed that both of the clusters might be formed outside the solar circle.
Northern Binaries in the Evrena Project
(Cambridge Univ Press, 2012) Bakış, V.; Hensberge, H.; Zejda, M.; de Cat, P.; Yılmaz, F.; Bloemen, S.; Svoboda, P.; Demircan, Osman
In the framework of the EVRENA project, high-resolution spectra. of northern eclipsing close binaries in stellar groups are obtained with the HERMES Echelle spectrograph at the Mercator telescope (Roque de los Muchachos Observatory). This contribution gives the first results on DV Camelopardalis.
On the existence of 'Maia variables'
(Cambridge Univ Press, 2024) Kahraman Aliçavuş, Filiz; Handler, Gerald; Chowdhury, Sowgata; Niemczura, Ewa; Jayaraman, Rahul; De Cat, Peter; Özuyar, Doğuş; Aliçavuş, Fahri
There are different classes of pulsating stars in the H-R diagram. While many of those classes are undisputed, some remain a mystery such as the objects historically called 'Maia variables'. Whereas the presence of such a class was suggested seven decades ago, no pulsational driving mechanism is known that could excite short-period oscillations in these late B to early A-type stars. Alternative hypotheses that would render the reports of variability of those stars erroneous have been proposed such as incorrect effective temperatures, binarity or rapid rotation, but no certain conclusions have been reached yet. Therefore, the existence of these variables as a homogeneous class of pulsating star is still under discussion. Meanwhile, many new candidates of these variables have been claimed especially by using photometric observations of space telescopes. In this study, we examined 31 objects that are alleged members of this hypothetical group and carried out detailed spectroscopic and photometric analyses to test the proposed hypotheses for their cause of variability. The T-eff, log g , v sin i , and chemical abundances of the targets were determined and the TESS photometric data were examined. As a result, we found that most of these targets are located inside the delta Scuti, beta Cephei, or SPB star instability strips, a few show evidence for binarity and others for rapid rotation. We give arguments that none of the apparently rapid pulsations in our targets is caused by a star outside any known instability strip. By extrapolation, we argue that most stars proposed as pulsators outside well-established instability domains are misclassified. Hence there is no sufficient evidence justifying the existence of a class of pulsating stars formerly known as the 'Maia variables'.
A comprehensive photometric analysis of the shallow contact binary IR Vir
(Elsevier, 2024) Yıldırım, Muhammed Faruk
The light curves (LC(s)) of the shallow contact binary (SCB(s)) IR Vir were retrieved from the TESS, Kepler (K2), ASAS, ASAS-SN, and KWS databases and comprehensively analyzed in this paper. For IR Vir, a q search was conducted to determine the mass ratio, which was found to be 0.371 +/- 0.008. The analysis indicates that IR Vir was a typical A-type W UMa. Since the determination of absolute parameters is crucial for analyzing the evolution of such systems, the masses of the bodies of IR Vir were estimated as M-1 = 1.03 +/- 0.10 M-circle dot, M-2 = 0.38 +/- 0.05 M-circle dot, and the radii as R-1 = 1.16 +/- 0.06 R-circle dot, R-2 = 0.73 +/- 0.04 R-circle dot. In the analysis of the orbital period (OP(s)) for IR Vir, it was found that the OP of IR Vir was increasing, and this value was calculated to be 0.0376 s per year. The OP increase can be explained by the conserved mass exchange between the bodies, and it can be proposed to be from the low mass body to the more one. This value was calculated as 2.4 x 10(-7) M-circle dot per year. Furthermore, a sinusoidal change in the OP was also identified, and it was proposed that this could be attributed to the presence of a third body or magnetic activity. Finally, to gain a better understanding of the nature of IR Vir, it was positioned in the logM(tot) - logJ and HR (Hertzsprung-Russell) diagrams.
Investigation of the stability of the extreme low mass ratio contact binaries SX Crv and XX Sex, which are analysed photometrically
(Elsevier Sci Ltd, 2024) Yıldırım, Muhammed Faruk
The photometric analyses of the extreme low mass ratio contact binaries SX Crv and XX Sex were conducted in detail. Light curves of SX Crv and XX Sex were retrieved from TESS, and light curve analyses were performed simultaneously with radial velocities. The mass ratios for SX Crv and XX Sex were calculated as 0.077(1) and 0.099(2). The masses of the primary components account for about 90% of the total masses of the systems and were determined to be 1.256(48) M (R) (R) and 1.337(37) M (R) (R) for SX Crv and XX Sex, respectively. It has been observed that the orbital periods of both systems have increased. The orbital period change rate of SX Crv has been calculated to be 0.39 s per century, while that of XX Sex has been calculated to be 2.68 s per century. The orbital angular momentum (Jo) o ) determined for both systems is more than 3 times the spin angular momentum (Js), s ), and it can be said that the SX Crv and XX Sex systems are stable. The calculated instability separation ( a ins. ) and instability mass ratio (q ins. ) values for both systems are smaller than those obtained in the analyses, which supports the stability. The estimated ages of the systems are 7.4 Gyr for SX Crv and 3.9 Gyr for XX Sex. logMtot tot - logJ and logTeff- eff - logL diagrams were also interpreted to better understand the evolution of the extreme low mass ratio contact binaries.
On the nature of the eccentric eclipsing binary star SY Phe with a pulsating ? Dor component
(Oxford Univ Press, 2024) Erdem, Ahmet; Sürgit, Derya; Engelbrecht, Chris A.; Zasche, Petr; Bakış, Volkan; Marang, Fred
Spectroscopic observations of the eccentric binary system SY Phe were made at the South African Astronomical Observatory in 2019, 2020, and 2021, and its mid-resolution spectra were obtained. The radial velocities of the component stars were measured using the cross-correlation method and Fourier disentangling of the spectra. The spectral type (hence the effective temperature) of the primary star was determined from a model-atmosphere analysis. The radial velocity and Transiting Exoplanet Survey Satellite ( TESS ) light curves of the system were analysed, and its absolute parameters were derived. A strong (5.2 mmag) periodic signal with a frequency typical of gamma Dor stars (1.169 cycles per day) dominates the Fourier spectrum of the light curve between the eclipses. Apsidal motion parameters of SY Phe were calculated by studying eclipse timing variations. The Geneva evolution models indicate an evolutionary age of 2 Gyr and solar metallicity for the primary component; however, although the position of the secondary component in the H-R diagram matches the isochrone of 2Gyr, it appears to have a larger radius and higher effective temperature than expected for its determined mass. Here, the secondary component has too large a radius, which is in accordance with the radius discrepancy problem that has been encountered in other studies, especially in late-type dwarfs, and has not been solved for half a century.
The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way
(Cambridge Univ Press, 2014) Eker, Z.; Bilir, Selçuk; Soydugan, Faruk; Yaz Gökçe, Esma; Soydugan, Esin; Tüysüz, Mehmet; Şenyüz, Tunç; Demircan, Oya
The most accurate stellar astrophysical parameters were collected from the solutions of the light and the radial velocity curves of 257 detached double-lined eclipsing binaries in the Milky Way. The catalogue contains masses, radii, surface gravities, effective temperatures, luminosities, projected rotational velocities of the component stars, and the orbital parameters. The number of stars with accurate parameters increased 67% in comparison to the most recent similar collection by Torres, Andersen, & Gimenez (2010). Distributions of some basic parameters were investigated. The ranges of effective temperatures, masses, and radii are 2 750 < T-eff (K)< 43 000, 0.18 < M/M-circle dot < 33, and 0.2 < R/R-circle dot < 21.2, respectively. Being mostly located in one kpc in the Solar neighborhood, the present sample covers distances up to 4.6 kpc within the two local Galactic arms, Carina-Sagittarius and Orion Spur. The number of stars with both mass and radius measurements better than 1% uncertainty is 93, better than 3% uncertainty is 311, and better than 5% uncertainty is 388. It is estimated from the Roche lobe filling factors that 455 stars (88.5% of the sample) are spherical within 1% of uncertainty.
Behaviors of dark energy and mesonic scalar field for anisotropic universe in f (R) gravity
(Elsevier, 2012) Aktaş, Can; Aygün, Sezgin; Yılmaz, İhsan
In this Letter, we study behaviors of dark energy in the form of perfect fluid and mesonic scalar field for Marder space-time which is anisotropic and homogeneous in f (R) gravity. Exact solutions of the modified Einstein field equations in f (R) gravity are obtained by using anisotropic features, of Marder space-time. We do not make any assumptions about f (R) function while we are solving f (R I equations. We have investigated dark energy behaviors in f (R) gravity. We have concluded that dark energy in our model behaves like phantom type. Also we have concluded that mesonic scalar field transforms to another matters into time. In our solutions, obtained f (R) functions existed by dark energy and mesonic scalar field are same like general one accepted in the literature. Furthermore, physical and kinematical quantities are examined for two matters, separately. Finally obtained solutions are discussed. (C) 2011 Elsevier B.V. All rights reserved.
Updated absolute parameters and kinematics of IS CMa
(Wiley-V C H Verlag Gmbh, 2024) Evcil, Serkan; Adalalı, Simge; Alan, Neslihan; Canbay, Remziye; Bilir, Selçuk
Eclipsing binary systems are significant objects for astrophysics in that direct observations can determine the fundamental parameters of stars. In this study, we precisely determined the fundamental parameters of the binary component stars obtained by simultaneous analysis of radial velocities and the TESS light curve using the Wilson and Devinney code. Following the analysis, the masses and radii of the primary and secondary components were determined as M1 = 1.58 +/- 0.01M(circle dot), M-2 = 0.48 +/- 0.02M(circle dot), and R-1 = 1.93 +/- 0.01R(circle dot), R-2 = 1.14 +/- 0.01R(circle dot), respectively. Furthermore, the distance of IS CMa is calculated as 92.7 +/- 6.5$$ 92.7\pm 6.5 $$ pc. On the basis of the analysis of the mid-eclipse times, it was found that the variation in the orbital period is represented by an upward parabola. It has an increasing rate of dP/dt = 1.09 x 10(-7). Using PARSEC stellar evolutionary tracks and isochrones with solar metallicity estimated the age of IS CMa as 1.3 +/- 0.1 Gyr. Kinematic and Galactic orbital parameters of IS CMa were obtained from the astrometric and spectroscopic data of the system. The Galactic orbit analysis reveals that IS CMa formed inside the solar circle and it is a member of the young thin-disc population.
Age Dependent Angular Momentum, Orbital Period and Total Mass of Detached Binaries
(Cambridge Univ Press, 2012) Demircan, Oya; Tüysüz, Mehmet; Soydugan, Faruk; Bilir, Selçuk
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.
Energy-momentum localization for Bianchi type-IV Universe in general relativity and teleparallel gravity
(Indian Acad Sciences, 2012) Aygun, Sezgin; Tarhan, İsmail
In this study we have investigated the energy-momentum distributions for homogeneous and an isotropic Bianchi type-IV in B class Universe. For this purpose, we have used energy-momentum complexes of Einstein, Bergmann-Thomson, Landau-Lifshitz (LL), Papapetrou, Tolman and Moller in general relativity (GR) as also Einstein, Bergmann-Thomson, Landau-Lifshitz and Moller in teleparallel gravity (TG). From the obtained results we have found that Einstein and Bergmann-Thomson distributions are exactly giving the same results in GR and TO but the Landau-Lifshitz, Papapetrou Tolman and Moller energy-momentum distributions do not provide the same results with Einstein and Bergmann-Thomson in OR and TG. Furthermore, Einstein, Bergmann-Thomson and LL results are the same in different gravitation theories and we get that both OR and TG are equivalent theories for these prescriptions. From the obtained solutions, we could say that these are equivalent theories. Also, Moller energy-momentum distributions do not give the same results in OR and TG. However, we have found that all energy prescriptions are negative and our results agree with Nester et al.
Single-lined eclipsing binaries with ? Scuti components: GQ Dra, RR Lep, and TYC 683-640-1
(Oxford University Press, 2024) Kahraman Aliçavuş, Filiz; Aliçavuş, Fahri; Çoban, Çağlar Gani; Handler, G.; De Cat, P.
Eclipsing binaries with (a) pulsating component(s) are remarkable objects to investigate the evolution and structure of stellar systems. Detailed studies of such systems are also important to reveal their pulsation properties. The largest sample of pulsating eclipsing binaries is the one containing δ Scuti variables. In this study, we present a comprehensive spectroscopic and photometric study of three such systems, GQ Dra, RR Lep, and TYC 683-640-1. Their orbital parameters were derived from their large-amplitude radial velocity variations. All systems were found to be single-lined eclipsing binaries. We determined the atmospheric parameters of the primary components, which are the more luminous ones. By using the results of the spectroscopic analysis, the binarity of the systems was modelled and the fundamental stellar parameters (mass, radius) of each system were obtained. In addition, the pulsations of the systems were analysed. Both GQ Dra and RR Lep exhibit frequencies that are modulated with the orbital period. Therefore, the pulsating components of these systems are identified as candidate tidally tilted pulsators.
First Detailed Photometric Investigation on the Nature of Contact Binary System AA Cet
(Institute of Physics, 2023) Yıldırım, Muhammed Faruk
The TESS light curve (LC) of the marginal contact binary AA Cet was analyzed simultaneously with the radial velocity and the orbital period (OP) change of the system was investigated. The physical parameters of the system were obtained by analyzing the LC of AA Cet with the Wilson-Devinney method, and the absolute parameters of the components were calculated using the results obtained. For the components of AA Cet, the masses and radii were calculated as M 1 = 1.39 ± 0.04 M ⊙, M 2 = 0.48 ± 0.02 M ⊙ and R 1 = 1.64 ± 0.03 R ⊙, R 2 = 1.01 ± 0.04 R ⊙, respectively. AA Cet is a marginal contact binary with a temperature difference of 1305 K between its components. A total of 14 eclipse times were obtained from the TESS data and used in the OP analysis together with those collected from the literature. It has been observed that the change in the OP of AA Cet is in the form of a decreasing parabola. Conservative mass transfer between the components has been interpreted as the reason for this change. The OP decrease amount of AA Cet was obtained as dP/dt = 0.0062 ± 0.0006 s yr−1, and the reason for this decrease was attributed to a 3.3(9) × 10−8 M ⊙ mass transfer per year from the more massive component to the less massive one. The age of AA Cet has been estimated as 7 Gyr, as the age of contact systems helps us to understand their evolution.
Comprehensive spectroscopic and photometric study of pulsating eclipsing binary star AI Hya
(Oxford University Press, 2023) Kahraman Alicavuş, Filiz; Aliçavuş, Fahri; Pawar, T.; Helminiak, K. G.; Handler, G.; Moharana, A.
The pulsating eclipsing binaries are remarkable systems that provide an opportunity to probe the stellar interior and to determine the fundamental stellar parameters precisely. Especially the detached eclipsing binary systems with (a) pulsating component(s) are significant objects to understand the nature of the oscillations since the binary effects in these systems are negligible. Recent studies based on space data have shown that the pulsation mechanisms of some oscillating stars are not completely understood. Hence, comprehensive studies of a number of pulsating stars within detached eclipsing binaries are important. In this study, we present a detailed analysis of the pulsating detached eclipsing binary system AI Hya which was studied by two independent groups with different methods. We carried out a spectroscopic survey to estimate the orbital parameters via radial velocity measurements and the atmospheric parameters of each binary component using the composite and/or disentangled spectra. We found that the more luminous component of the system is a massive, cool and chemically normal star while the hotter binary component is a slightly metal-rich object. The fundamental parameters of AI Hya were determined by the analysis of binary variations and subsequently used in the evolutionary modelling. Consequently, we obtained the age of the system as 850 ± 20 Myr and found that both binary components are situated in the δ Scuti instability strip. The frequency analysis revealed pulsation frequencies between 5.5 and 13.0 d−1 and we tried to estimate which binary component is the pulsating one. However, it turned out that those frequencies could originate from both binary components.
First photometric study of three eclipsing binary star systems: V495 Aur, V589 Aur and V478 Cam
(Elsevier B.V., 2023) Öztürk, Oğuz; Erdem, Ahmet
The light curve solutions and orbital period analysis of V495 Aur, V589 Aur and V478 Cam eclipsing binary star systems are presented for the first time in this study. Transiting Exoplanet Survey Satellite (TESS) observations were used as observational data. From the light curve solutions, it was concluded that all three systems are semi-detached binary star systems in which the secondary components fill their Roche lobes. The absolute parameters of the systems were also estimated. Accordingly, the photometric mass ratios of V495 Aur, V589 Aur and V478 Cam are found to be 0.251±0.035, 0.254±0.038 and 0.078±0.010, respectively. Upward parabolic change was observed in the O-C diagrams of all the systems considered. As a result of parabolic changes, we concluded that the orbital periods of the V495 Aur, V589 Aur and V478 Cam systems increased secularly with a rate of 0.050±0.010 s/year, 0.018±0.004 s/year and 0.070±0.015 s/year, respectively. The increases in orbital periods are explained by the dominant mass transfer mechanism from the secondary components to the primary components. In addition, the mass transfer rates between components and the rates of mass lost from the systems were estimated.

Güncel Gönderiler