Yazar "Zasche, P." seçeneğine göre listele

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    Absolute Parameters of Three F Type Southern Eclipsing Binary Stars: VW Ret, FW Vel, and CW Eri
    (Copernicus Foundation for Polish Astronomy, 2024) Zasche, P.; Sürgit, D.; Erdem, A.; Marang, F.; Engelbrecht, C.A.
    This study presents the first detailed analysis of three southern eclipsing binaries. Both – light curves and radial velocity curves – were studied together with their period changes, revealing basic physical and orbital properties of these systems. All three stars, VW Ret, FW Vel, and CW Eri are detached binaries with a few days orbital period. Thanks to our detailed analysis we revealed that all the component stars are slightly heavier than the Sun, laying in the mass range between 1.3 M and 1.6 M . The systems VW Ret, and FW Vel seem to have more dominant secondary components, both in the masses, as well as in luminosities. The system VW Ret is a triple star showing large eclipse times variations with the periodicity of 4 yr. For FW Vel a similar weak variation was also found, but with much lower amplitude of about 56 s only, needed to be independently confirmed. CW Eri shows slightly eccentric orbit (e = 0.015), but only very slow apsidal motion. Moreover, its ages for both component do not agree with each other very well. Hence, it provides a challenge for future more detailed modeling of this interesting system. © 2024 Copernicus Foundation for Polish Astronomy. All rights reserved.
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    First detailed study of two eccentric eclipsing binaries: TYC 5378-1590-1 and TYC 8378-252-1
    (Edp Sciences S A, 2023) Zasche, P.; Surgit, D.; Erdem, A.; Engelbrecht, C. A.; Marang, F.
    Aims. The analysis of combined photometry and spectroscopy of eccentric eclipsing binary systems facilitates the derivation of very precise values for a large ensemble of physical parameters of the component stars and their orbits, thereby providing stringent tests of theories of stellar structure and evolution. In this paper two eccentric eclipsing binary systems, TYC 5378-1590-1 and TYC 8378252-1, are studied in detail for the first time. Methods. Radial velocities were obtained using cross-correlation methods applied to mid-resolution spectra covering almost the entire orbital phase domains of these two systems. TESS photometry was used for the analysis of TYC 5378-1590-1, whereas ASAS-SN photometry was used for the analysis of TYC 8378-252-1. Results. We obtained the first precise derivation of the physical parameters of these systems. Both systems display moderately eccentric orbits (e similar to 0:3 and 0:2) with periods of 3.73235 and 2.87769 days, respectively. The apsidal motion is very slow, with a duration of several centuries for both systems. We present two models for the apsidal motion of TYC 5378-1590-1. The internal structure constant derived from observations for TYC 8378-252-1 is approximately 11% lower than theoretical predictions. We discuss possible reasons for this discrepancy. Our analysis indicates that the components of both systems are on the main sequence. The components of TYC 5378-1590-1 are relatively young stars (age similar to 600 Myr) close to the ZAMS, whereas the components of TYC 8378-252-1 are relatively old stars (age similar to 4 Gyr) close to the TAMS. Our finding that the circularization timescale for TYC 5378-1590-1 is similar to 200 times longer than its evolutionary age is compatible with circularization theory; however, our finding that the evolutionary age of TYC 8378-252-1 is approximately ten times longer than the circulation age, while its orbital eccentricity is quite high (e similar to 0:2), challenges the present theories of circularization.
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    Survey for ? Sct components in eclipsing binaries and new correlations between pulsation frequency and fundamental stellar characteristics
    (Oxford Univ Press, 2012) Liakos, A.; Niarchos, P.; Soydugan, Esin; Zasche, P.
    CCD observations of 68 eclipsing binary systems, candidates for containing delta Scuti components, were obtained. Their light curves are analysed using the (PERIOD)04 software for possible pulsational behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to determine their geometrical and pulsational characteristics. Spectroscopic observations of WY Cet and UW Cyg were used to estimate the spectral class of their primary components, while for HZ Dra radial velocities of its primary were measured. O - C diagram analysis was performed for the cases showing peculiar orbital period variations, namely CZ Aqr, TY Cap, WY Cet and UW Cyg, with the aim of obtaining a comprehensive picture of these systems. An updated catalogue of 74 close binaries including a delta Scuti companion is presented. Moreover, a connection between orbital and pulsation periods, as well as a correlation between evolutionary status and dominant pulsation frequency for these systems, is discussed.