Yazar "Engelbrecht, C. A." seçeneğine göre listele
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Öğe Absolute Parameters of Detached Binaries in the Southern Sky - I: V349 Ara and V4403 Sgr(Cambridge Univ Press, 2015) Erdem, A.; Surgit, D.; Engelbrecht, C. A.; Van Heerden, H. P.We present the first analysis of spectroscopic and photometric observations of the two southern eclipsing binary stars, V349 Ara and V4403 Sgr. Radial velocity curves of these two systems obtained at the South African Astronomical Observatory and their V light curves from the All Sky Automated Survey were solved simultaneously using the Wilson-Devinney code. Our photometric models describe these two systems as Algol-like binary stars with detached configurations. The masses and radii were found to be 2.59 +/- 0.07 M, 3.60 +/- 0.07 R and 2.51 +/- 0.06 M, 4.15 +/- 0.07 R for the primary and secondary components of V349 Ara, respectively. Those of V4403 Sgr were derived to be 1.33 +/- 0.02 M, 1.74 +/- 0.02 R and 1.59 +/- 0.03 M, 2.50 +/- 0.03 R for the primary and secondary components, respectively. The distances to V349 Ara and V4403 Sgr were computed to be 677 +/- 36 and 199 +/- 10 pc from the dynamic parallax, respectively, taking into account interstellar extinction. The evolution cases of these two systems are also examined. Both components of these two systems are evolved main-sequence stars, and the dynamic ages were estimated as approximately 0.67 and 2.29 Gyr for V349 Ara and V4403 Sgr, respectively, when compared to Geneva theoretical evolution models.Öğe Absolute parameters of detached binaries in the southern sky - III: HO Tel(Elsevier Science Bv, 2017) Surgit, D.; Erdem, A.; Engelbrecht, C. A.; van Heerden, H. P.; Manick, R.We present the first radial velocity analysis of the southern eclipsing binary star HO Tel, based on spectra obtained at the South African Astronomical Observatory in 2013. The orbital solution of this neglected binary gave the quite large spectroscopic mass ratio of 0.921(+/- 0.005). The V light curve from the All Sky Automated Survey (ASAS) and Walraven five-colour (WULBV) photometric light curves (Spoelstra and Van Houten 1972) were solved simultaneously using the Wilson-Devinney code supplemented by the Monte Carlo search method. The final photometric model describes HO Tel as a detached binary star where both component stars fill about three-quarters of their Roche limiting lobes. The masses and radii were found to be 1.88(+/- 0.04) M-circle dot, 2.28(+/- 0.15) R-circle dot and 1.73(+/- 0.04) M-circle dot, 2.08(+/- 0.16) R-circle dot for the primary and secondary components of the system, respectively. The distance to HO Tel was calculated as 282(+/- 30) pc, taking into account interstellar extinction. The evolution case of HO Tel was also examined. Both components of the system are evolved main-sequence stars with an age of approximately 1.1 Gy, when compared to Geneva theoretical evolution models. (C) 2017 Elsevier B.V. All rights reserved.Öğe Absolute parameters of eclipsing binaries in Southern Hemisphere sky - II: QY Tel(Elsevier Science Bv, 2016) Erdem, A.; Surgit, D.; Engelbrecht, C. A.; van Heerden, H. P.; Manick, R.This paper presents the first analysis of spectroscopic and photometric observations of the neglected southern eclipsing binary star, QY Tel. Spectroscopic observations were carried out at the South African Astronomical Observatory in 2013. New radial velocity curves from this study and V light curves from the All Sky Automated Survey were solved simultaneously using modern light and radial velocity curve synthesis methods. The final model describes QY Tel as a detached binary star where both component stars fill at least half of their Roche limiting lobes. The masses and radii were found to be 1.32 (+/- 0.06) M-circle dot, 1.74 (+/- 0.15) R-circle dot and 1.44 (+/- 0.09) M-circle dot, 2.70 (+/- 0.16) R-circle dot for the primary and secondary components of the system, respectively. The distance to QY Tel was calculated as 365 (+/- 40) pc, taking into account interstellar extinction. The evolution case of QY Tel is also examined. Both components of the system are evolved main-sequence stars with an age of approximately 3.2 Gy, when compared to Geneva theoretical evolution models. (C) 2016 Elsevier B.V. All rights reserved.Öğe Absolute parameters of southern eclipsing binary: MW Pup(Elsevier Science Bv, 2015) Surgit, D.; Erdem, A.; Engelbrecht, C. A.This paper presents the first analysis of spectroscopic and photometric observations of the southern eclipsing binary star MW Pup. ASAS V light and SAAO radial velocity curves of the system were solved simultaneously using Wilson-Devinney code. The results describe MW Pup as an Algol-like binary star with a detached configuration. The masses of the components were found to be 2.20 +/- 0.06 and 1.88 +/- 0.07 M-circle dot and the radii to be 1.84 +/- 0.03 and 1.72 +/- 0.03 R-circle dot for primary and secondary components, respectively. The distance to MW Pup was calculated to be 430 +/- 30 pc from the dynamic parallax, neglecting interstellar absorption, in agreement with the value derived from the eclipse-parallax method. The evolution of the system is also discussed. Both components are unevolved Main Sequence stars and the dynamic age of the system is estimated as 263 +/- 70 My when compared to theoretical evolution models. (C) 2014 Elsevier B.V. All rights reserved.Öğe 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.Öğe First Spectroscopic Solutions of Two Southern Eclipsing Binaries: HO Tel and QY Tel(Astronomical Soc Pacific, 2015) Surgit, D.; Erdem, A.; Engelbrecht, C. A.; van Heerden, P.; Manick, R.We present preliminary results from the analysis of spectroscopic observations of two southern eclipsing binary stars, HO Tel and QY Tel. The grating spectra of these two systems were obtained at the Sutherland Station of the South African Astronomical Observatory in 2013. Radial velocities of the components were determined by the Fourier disentangling technique. Keplerian radial velocity models of HO Tel and QY Tel give their mass ratio as 0.921 +/- 0.005 and 1.089 +/- 0.007, respectively.
