Yazar "Alicavus, Fahri" seçeneğine göre listele

Listeleniyor 1 - 7 / 7
  • [ X ]
    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, Faruk
    In 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.
  • [ X ]
    Öğe
    Detailed analysis of an eccentric TESS binary star with solar-type components: TIC 284613090
    (Elsevier, 2022) Alicavus, Fahri
    Eclipsing 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.
  • [ X ]
    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, Fahri
    W 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.
  • [ X ]
    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, Selcuk
    In 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.
  • [ X ]
    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, Sareh
    New 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.
  • [ X ]
    Öğe
    Photometric Analysis of Kepler Contact Binaries With Large Fill-Out Factors: KIC 3221207 and KIC 6677225
    (Amer Inst Physics, 2017) Alicavus, Fahri; Soydugan, Faruk
    Contact 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.
  • [ X ]
    Öğe
    Precise Analysis of Two Kepler Detached Eclipsing Binary Stars KIC 3327980 and KIC 10156064
    (Amer Inst Physics, 2017) Alicavus, Fahri; Soydugan, Faruk
    Stars 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.