Yazar "Kahraman Alicavus, Filiz" seçeneğine göre listele

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    Absolute parameters of young stars: NO Puppis
    (Cambridge Univ Press, 2025) Erdem, Ahmet; Bakis, Volkan; Southworth, John; Rhodes, Michael; Kahraman Alicavus, Filiz; Budding, Edwin; Blackford, Mark G.
    The southern early-type, young, eccentric-orbit eclipsing binary NO Puppis forms the A component of the multiple star Gaia DR3 5528147999779517568. The B component is an astrometric binary now at a separation of about 8.1 arcsec. There may be other fainter stars in this interesting but complex stellar system. We have combined several lines of evidence, including TESS data from four sectors, new ground-based BVR photometry, HARPS (ESO) and HERCULES (UCMJO) high-resolution spectra and astrometry of NO Pup. We derive a revised set of absolute parameters with increased precision. Alternative optimal curve-fitting programs were used in the analysis, allowing a wider view of modelling and parameter uncertainties. The main parameters are as follows: M-Aa = 3.58 +/- 0.11, M-Ab = 1.68 +/- 0.09 (M-circle dot); R-Aa=2.17 +/- 0.03, R-AB=1.51 +/- 0.06 (R-circle dot), and T-eAa= 13 300 +/- 500, T-eAb =7400 +/- 500 (K). We estimate approximate masses of the wide companions, Ba and Bb, as M-Ba = 2.0 and M-Bb 1.8 (M-circle dot). The close binary's orbital separation is a = 8.51 +/- 0.05 (R-circle dot); its age is approximately 20 Myr and distance 172 +/- 1 pc. The close binary's secondary (Ab) appears to be the source of low amplitude delta Scuti-type oscillations, although the form of these oscillations is irregular and unrepetitive. Analysis of the lambda 6678 He I profile of the primary show synchronism of the mean bodily and orbital rotations. The retention of significant orbital eccentricity, in view of the closeness of the A-system components, is unexpected and poses challenges for the explanation that we discuss.
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    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, Marina
    Pulsating 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.
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    Spectroscopic and photometric investigation of some potentially chemically peculiar ? Scuti stars
    (Oxford Univ Press, 2025) Kahraman Alicavus, Filiz; Alicavus, Fahri; Ozkardes, Burcu; Celik, Eda
    Investigating 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.
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    The evolutionary status of chemically peculiar eclipsing binary star DV Boo
    (Natl Astronomical Observatories, Chin Acad Sciences, 2020) Kahraman Alicavus, Filiz; Alicvus, F.
    Eclipsing binary systems are unique stellar objects to examine and understand stellar evolution and formation. Thanks to these systems, the fundamental stellar parameters (mass, radius) can be obtained very precisely. The existence of metallic-line (Am) stars in binaries is noticeably common. However, the known number of Am stars in eclipsing binaries is less. The Am stars in eclipsing binaries are extremely useful to deeply investigate the properties of Am stars, as eclipsing binaries are the only tool to directly derive the fundamental stellar parameters. Additionally, the atmospheric parameters and metallicities of such binary components could be obtained by a detailed spectroscopic study. Therefore, in this study, we present a comprehensive photometric and spectroscopic analysis of the eclipsing binary system DV Boo which has a possible Am component. The fundamental stellar parameters were determined by the analysis of radial velocity and photometric light curves. The atmospheric parameters of both binary components of DV Boo were derived considering the disentangled spectra. The chemical abundance analysis was carried out as well. As a result, we showed that the primary component exhibits a typical Am star chemical abundance distribution. The fundamental stellar parameters of the binary components were also obtained with an accuracy of <1% for masses and <3% for radii. The evolutionary status of DV Boo was examined utilizing the precisely obtained stellar parameters. The age of the system was found to be 1.00 +/- 0.08 Gyr.