Yazar "Alicavus, Fahri" seçeneğine göre listele
Listeleniyor 1 - 12 / 12
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe BSN-III: The First Multiband Photometric Study on the Eight Total Eclipse Contact Binary Stars(Iop Publishing Ltd, 2025) Poro, Atila; Li, Kai; Michel, Raul; Wang, Li-Heng; Alicavus, Fahri; Alizadeh, Ghazal; Altamirano-Devora, LilianaThis study continues our in-depth investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight new systems, complementing our previous work. Multiband BVRcIc photometric data were acquired through ground-based observations at an observatory in Mexico, from which new times of minima were determined. Our analysis of orbital period variations using the O - C method revealed that one system shows no long-term variation, four systems exhibit a secular decrease in their orbital periods, and two systems exhibit a secular increase, suggesting mass transfer between the components. Notably, one system displays a cyclic variation with an amplitude of 0.00865 days and a period of 10.49 yr, which we attribute to the light travel time effect induced by a tertiary companion, possibly a brown dwarf. We modeled the light curves using the PHysics Of Eclipsing BinariEs Python code. Six of the target systems required the inclusion of a cold starspot on one of the system's stars due to the asymmetry observed in the maxima of their light curves. Absolute parameters were estimated using the Gaia DR3 parallax method. Using the components' effective temperatures and masses, we classified five of the systems as W-subtype and three as A-subtype. The stellar evolution was illustrated through the mass-radius and mass-luminosity diagrams. Furthermore, we investigated the dynamical stability of two systems with extremely low mass ratios.Öğe BSN. II. The First Light Curve Study of Eight Total Eclipsing Contact Binary Stars with Shallow Fillout Factors(Iop Publishing Ltd, 2025) Poro, Atila; Li, Kai; Michel, Raul; Wang, Li-Heng; Alicavus, Fahri; Najera, Morgan Rhai; Santillan-Ortega, PriscilaThis study provides the first comprehensive analysis of eight total-eclipse W Ursae Majoris-type contact binary systems. Ground-based photometric multiband observations were conducted at a Mexican observatory, and new times of minima were extracted. The O-C analysis reveals that four of our target binaries exhibit a long-term increase in their orbital periods, while the others show a long-term decrease in their orbital periods. We analyzed the light curves using the PHOEBE Python code and BSN application. Among the target systems, two required the inclusion of a cold starspot on one of the components to achieve an adequate fit. The light curve analysis revealed that the target systems exhibit a shallow fillout factor. Absolute parameters were estimated using the Gaia DR3 parallax and astrophysics equations. Considering the effective temperatures and component masses, each system was classified as either the A- or W-subtype. The stellar evolution of the systems was represented through the mass-radius and mass-luminosity diagrams. Additionally, we calculated the initial masses of the companion stars and the total mass lost for each target system.Öğe BSN. V. The First Detailed Light Curve Modeling of Eight Totally Eclipsing Contact Binary Stars Using Ground-based and TESS Observations(Iop Publishing Ltd, 2025) Poro, Atila; Michel, Raul; Javier Tamayo, Francisco; Hedayatjoo, Mahya; Aceves, Hector; Alicavus, FahriThis study broadens our comprehensive investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight additional systems, continuing our previous research. Multiband BV RcIc photometric data were obtained at an observatory in Mexico, from which new times of minima were determined. All target systems also had available space-based Transiting Exoplanet Survey Satellite time-series data. Orbital period variations were studied for eight target systems, showing either linear or parabolic trends. The target systems exhibiting parabolic trends demonstrated a sustained decrease in their orbital periods over time. We modeled the light curves utilizing the PHOEBE Python code in combination with the BSN application. We revisited the relationship between orbital period and the temperature of the hotter component in contact binary systems using an empirical approach. Our analysis identified a clear break at P = 0.27 day, separating the systems into two distinct groups for orbital periods shorter than 0.6 day. Following the determination of stellar extinction, absolute parameters for seven systems were estimated employing parallax measurements from Gaia DR3. Based on the components' effective temperatures and masses, the systems were classified into A- and W-subtypes. Their evolutionary states were illustrated using mass-radius and mass-luminosity diagrams.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 Detailed analysis of an eccentric TESS binary star with solar-type components: TIC 284613090(Elsevier, 2022) Alicavus, FahriEclipsing binary stars are significant objects for understanding stellar evolution, stellar population synthesis, and galaxy dynamics. Thanks to the increasing number of high-quality photometric data of space observations, the sensitivity of the fundamental astrophysical parameters (mass M, radius R) has risen and this situation has highlighted the importance of eclipsing binary stars once again. There are known relations between M and luminosity (L) for the eclipsing binary systems, especially for the detached binaries. However, in these M - L relations, some break-points appear and those points need to be re-examined with accurate M and L parameters of stars located at these areas. One of these break-points presents around the Solar mass. Therefore, this study focuses on a TESS field object TIC 284613090 which is an eccentric binary system containing two solar-type components. In the study, the fundamental parameters of the binary component stars were precisely obtained by a simultaneous analysis of the radial velocities and the TESS light curve. As a result, the masses and radii of the primary and secondary binary components were found to be M-1 = 1.030 (8) M-circle dot, M-2 =1.019 (8) M-circle dot and R-1 = 1.611 (5)R-circle dot, R-2 = 1.485 (5) R-circle dot, respectively. When the evolutionary status of the component stars was examined, it turned out that they are approaching the end of their main sequence evolution and the age of the system is 9.65 (20) Gyr. As a result of binary evolutionary models, it was also found that TIC 284613090 started its evolution with an orbital period of 11.83 days and an eccentric orbit with a value of e = 0.227. The position of the binary components in the M - L relation was examined as well and showed consistency with the relation.Öğe Investigation of near-contact semi-detached binary WUMi through observations and evolutionary models(Natl Astronomical Observatories, Chin Acad Sciences, 2020) Soydugan, Faruk; Soydugan, Esin; Alicavus, FahriW UMi is a near contact, semi-detached, double-lined eclipsing binary star with an orbital period of 1.7 d. Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysical parameters of the binary and its component stars. We determined mass and radius to be M-1 = 3.22 +/- 0.08 M-circle dot, R-1 = 3.63 +/- 0.04 R-circle dot for the primary star and M-2 = 1.44 +/- 0.05 M-circle dot, R-2 = 3.09 +/- 0.03 R-circle dot for the secondary star. Based on analysis of mid-eclipse times, variation in the orbital period is represented by a cyclic term and a downward parabola. Mass loss from the system is suggested for a secular decrease (-0.02 s yr(-1)) in the period. Both the mechanisms of a hypothetical tertiary star orbiting around W UMi and the surface magnetic activity of the less massive cooler companion were used to interpret periodic changes. Observational parameters were found to be consistent with binary stellar evolution models produced in the non-conservative approach of MESA at a higher metallicity than the Sun and an age of about 400 Myr for the system. Evidence that the system is rich in metal was obtained from spectral and kinematic analysis as well as evolution models. W UMi, a high mass ratio system compared to classical semi-detached binaries, is an important example since it is estimated from binary evolutionary models that the system may reach its contact phase in a short time interval.Öğe Kepler Binary Stars in the NGC 6819 Open Cluster: KIC 5113146 and KIC 5111815(Iop Publishing Ltd, 2020) Soydugan, Esin; Alicavus, Fahri; Soydugan, Faruk; Bilir, SelcukIn this study, an investigation of two double-lined binary stars KIC 5113146 and KIC 5111815 in the NGC 6819 open cluster is presented based on both photometric and spectroscopic data. Simultaneous analysis of light and radial velocity curves was made and the absolute parameters of the systems' components were determined for the first time. We find that both systems have F-type main-sequence components. The masses and radii were found to be M-1 = 1.29 +/- 0.02M(circle dot), R-1 = 1.47 +/- 0.03 R-circle dot and M-2 = 1.19 +/- 0.02 M-circle dot, R-2 = 1.13 +/- 0.02 R-circle dot for the primary and secondary components of KIC 5113146; and M-1 = 1.51 +/- 0.08 M-circle dot, R-1 = 2.02 +/- 0.05 R-circle dot and M-2 = 1.19 +/- 0.07 M-circle dot, R-2 = 1.32 +/- 0.04 R-circle dot for the components of KIC 5111815, respectively. The evolutionary status of the components was evaluated based on the MESA evolutionary tracks and isochrones. The ages of KIC 5111815 and KIC 5113146 were derived to be about 2.50 +/- 0.35 Gyr and 1.95 +/- 0.40 Gyr, respectively. Photometric distances were calculated to be 2850 +/- 185 pc for KIC 5113146 and 3120 +/- 260 pc for KIC 5111815. The results reveal that both KIC 5113146 and KIC 5111815 systems are the most likely members of NGC 6819.Öğe New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions(De Gruyter Poland Sp Z O O, 2020) Davoudi, Fatemeh; Poro, Atila; Alicavus, Fahri; Halavati, Afshin; Doostmohammadi, Saeed; Shandadi, AmirAbbas; Vahedi, SarehNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system's orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m(3)) = 0.0058 M-circle dot in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O'Connell effect was not seen in the light curve and there is no need to add spot.Öğe Photometric Analysis of Kepler Contact Binaries With Large Fill-Out Factors: KIC 3221207 and KIC 6677225(Amer Inst Physics, 2017) Alicavus, Fahri; Soydugan, FarukContact binary stars have an important role to understand how the binary stars evolve to a single star and explain to the physical processes of star merges. Hence, understanding of different type of contact binaries is valuable to explore sonic physical processes such as angular momentum loses, mass and heat transfers between components. In this study, we present the photometric analysis of two Kepler binary stars KIC 3221207 and KIC 6677225. As a result, it was found that both eclipsing binaries have large amount of common envelopes. The till-out factors of stars were determined to be 79 and 89 percent for KIC 3221207 and KIC 6677225, respectively. Furthermore, both systems show parabolic orbital period variations, while the third light contribution was found for KIC 3221207. In the result, we compare the target systems with similar, well-known contact binaries.Öğe Precise Analysis of Two Kepler Detached Eclipsing Binary Stars KIC 3327980 and KIC 10156064(Amer Inst Physics, 2017) Alicavus, Fahri; Soydugan, FarukStars are one of the most important objects to understand how the galaxies are formed; shaped and evolved. Hence, the determination of the absolute parameters of stars plays a crucial role. The absolute parameters (e.g. mass and radii) of the detached eclipsing binary stars could be determined with well accuracy. These accurate parameters could be used for understanding of the evolutional status of single stars in detailed. In this study, we carried out light curve solutions of two well-detached binaries KIC 3327980 and KIC 10156064 which were observed by Kepler space telescope. As a result, mass and radii of primary and secondary components were derived as M-1 = 1.64M(circle dot), M-2 = 1.42M(circle dot), R-1 = 2.08R(circle dot), R-2 = 1.66R(circle dot) for KIC 3327980 and M-1 = 1.67M(circle dot), M-2 = 1.05M(circle dot); R-1 = 1.92R(circle dot); R-2 = 1.06R(circle dot) for KIC 10156064. Additionally, the evolutionary status of the components of the systems were discussed and compared with the evolutional status of the other detached eclipsing binaries.Öğe Pulsating and Nonpulsating Components of Detached Eclipsing Binaries in the ? Scuti Instability Strip(Iop Publishing Ltd, 2025) Kahraman Alicavus, Filiz; Alicavus, Fahri; Celik Orhan, Zeynep; Celik, Eda; Catanzaro, Giovanni; Giarrusso, MarinaPulsating detached eclipsing binary systems are crucial for studying the internal structure of oscillating stars. These systems are advantageous because binary effects on pulsations are minimal, allowing for more accurate determinations of fundamental stellar parameters such as mass and radius. They serve as unique laboratories for detailed investigations of pulsating stars. In this study, we focused on four detached eclipsing binaries exhibiting delta Scuti-type oscillations: HD 117476, 205 Dra, HY Vir, and V1031 Ori. Our preliminary investigation showed that all binary components of these targets lie within the delta Scuti instability strip. Therefore, we aimed to determine which components are pulsating and which are not and to explore the differences between them. To achieve this, we analyzed TESS photometric data and high-resolution spectra of the targets. Radial velocity (RV) variations were measured, and atmospheric parameters for each component were derived using spectral disentangling or synthetic composite spectra. We also modeled the binary light and RV curves to determine the fundamental physical parameters of the components. Furthermore, we examined pulsation properties using three different approaches to identify the pulsating components. The evolutionary status of the targets was also assessed. Our analysis revealed that, in each system, only one component exhibits delta Scuti-type pulsations, while the others are nonpulsating. Interestingly, we found that the key difference between pulsating and nonpulsating components within the same binary is metallicity: the metal-rich components were found to be nonpulsators, supporting theoretical studies on the effect of metallicity on delta Scuti-type pulsations.Öğe Spectroscopic and photometric investigation of some potentially chemically peculiar ? Scuti stars(Oxford Univ Press, 2025) Kahraman Alicavus, Filiz; Alicavus, Fahri; Ozkardes, Burcu; Celik, EdaInvestigating chemically peculiar pulsating stars is crucial for understanding the pulsation driving mechanism in detail. To reveal the true peculiarity properties of stars, detailed spectroscopic analysis is essential. Therefore, in this study, we focused on delta Scuti stars previously identified as chemically peculiar but which needed comprehensive updated spectroscopic analysis to uncover their chemical abundance structure. We selected 10 targets which have publicly available high-resolution spectroscopic and photometric data. Performing spectral analyses, we determined the spectral classification, atmospheric parameters, and detailed chemical abundance distributions of the selected stars. The pulsation properties were also analyzed using TESS data, and pulsation modes for the highest amplitude pulsation frequencies were derived. We estimated the masses and ages of the targets using the evolutionary tracks and isochrones. As a result of our study, we show that only three targets exhibit chemical peculiarity: AU Scl and FG Eri as metallic A (Am) stars, and HZ Vel as a lambda Bootis. However, others were found to be chemically normal stars. This study show us the importance of chemical abundance analysis in the classification of chemical peculiar stars.
