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Öğe A W UMa type system from Southern Hemisphere: CN Hydri(Elsevier, 2009) Ozkardes, B.; Erdem, A.; Bakis, V.We present an analysis of the Hipparcos photometry and the high-resolution (lambda/Delta lambda = 41000) spectroscopy of the W UMa type system CN Hyi obtained in this study for the first time. The high resolution spectroscopic observations of the system were made at Mt. John University Observatory by using HERCULES fibre-fed echelle spectrograph in September 2007. The radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The orbital solution of CN Hyi yielded the spectroscopic mass ratio as 0.189. We performed the simultaneous solution of the Hipparcos light curve and the radial velocity curves. The light contribution of the third star to the total light of the system was also considered during our photometric analysis. The Simultaneous solutions yielded the absolute parameters of the system as M-1 = 1.37 M-1, M-2 = 0.25 M-2 for the masses, R-1 = 1.60 R-1, R-2 = 0.77 R-2, for the radii, and M-v.1, = 3(m).23, M-v.2 = 4(m).92 for the absolute magnitudes of the primary and secondary components, respectively. The distance of the system was calculated as 56 pc using the distance modulus with the corrections of the interstellar extinction. The positions of the components of CN Hyi in the FIR diagram were also discussed. (C) 2009 Elsevier B.V. All rights reserved.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 Absolute parameters of the newly-identified contact binary star IS Canis Major(Elsevier Science Bv, 2010) Ozkardes, B.; Erdem, A.This paper presents the results of the first high-resolution spectroscopic observations of the Southern W UMa type system IS CMa. Spectroscopic observations of the system were made at Mt. John University Observatory using a HERCULES fibre-fed echelle spectrograph in September 2007. The first radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The resulting orbital elements of IS CMa are: a(1) sin i = 0.0041 +/- 0.0001 AU, a(2) sin i = 0.0135 +/- 0.0001 AU, M(1) sin(3) i = 1.48 +/- 0.01 M(circle dot), and M(2) sin(3) i = 0.44 +/- 0.01 M(circle dot). The components were found to be in synchronous rotation taking into account the disentangled H(delta) line profiles of both components of the system. The Hipparcos light curve was solved by means of the Wilson-Devinney method supplemented with a Monte Carlo type algorithm. The radial velocity curve solutions including the proximity effects give the mass ratio of the system as 0.297 +/- 0.001. The combination of the Hipparcos light and radial velocity curve solutions give the following absolute parameters of the components: M(1) = 1.68 +/- 0.04 M(circle dot), M(2) = 0.50 +/- 0.02 M(circle dot), R(1) = 2.00 +/- 0.02 R(circle dot), R(2) = 1.18 +/- 0.03 R(circle dot), L(1) = 7.65 +/- 0 60. L(circle dot) and L(2) = 1.99 +/- 0.80 L(circle dot), The distance to IS CMa was calculated as 87 +/- 5 pc using the distance modulus with corrections for interstellar extinction. The position of the components of IS CMa in the HR diagram are also discussed: the system seems to have an age of 1.6 Gyr. (C) 2009 Elsevier B.V. All rights reserved.Öğe 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.Öğe Absolute parameters of young stars - II. V831 Centauri(Oxford Univ Press, 2010) Budding, E.; Erdem, A.; Inlek, G.; Demircan, O.Literature photometry and new high-resolution spectroscopy of V831 Cen are presented and analysed. Light and radial velocity curve fittings confirm the central pair of this young multiple system to be close to contact. Absolute parameters are found as follows: M-1 = 4.08 +/- 0.07 M-circle dot, M-2 = 3.35 +/- 0.06 M-circle dot, R-1 = 2.38 +/- 0.03 R-circle dot, R-2 = 2.25 +/- 0.03 R-circle dot, T-1 = 13 000 +/- 300 K, T-2 = 11 800 +/- 300 K; distance of 110 +/- 10 pc and age of similar to 20 +/- 5 Myr. Detailed examination of the spectrograms indicates the third component (V831 Cen B) to be an Ap star. The orbit of the third star about the close binary is analysed using historic astrometric measurements. This allows an estimate of the third star's mass to be about 2.5 M-circle dot, but this is sensitive to the adopted distance and inclination values. It is, however, confirmed by the measured radial velocity of the third star. To some extent, such analysis can also be applied to the fourth star (V831 Cen C). The derived properties can be checked against the system's membership of the Scorpius-Centaurus OB2 association.Öğe Absolute parameters of young stars: HX Velorum(Oxford Univ Press, 2019) Blackford, M. G.; Erdem, A.; Surgit, D.; Ozkardes, B.; Budding, E.; Butland, R.; Demircan, O.We present combined photometric and spectroscopic analyses of the southern multiple star HX Vel. High-resolution spectra of this system were taken at the University of Canterbury Mt. John Observatory in the years 2009-2015. Absolute parameters for HX Vel tend to confirm its young and near-main-sequence nature. We specify the main adopted parameters of the (non-eclipsing) close binary as follows: M-1 = 8.5 +/- 1.7, M-2 = 5.4 +/- 1.2, R-1 = 5.0 +/- 0.3, R-2 = 3.1 +/- 0.2, (circle dot); T-1 25 000 +/- 1300, T-2 20 000 +/- 2500 (K); systemic M-V -4.2 +/- 0.2. These parameters are sensitive to the low inclination, where we find a small disparity between the photometrically optimal 28 +/- 2 degrees and an adopted value of 26 degrees that gives better consistency with main-sequence stellar modelling. The relationship of HX Vel to the galactic cluster IC 2395 and OB association Vela OB1C is also considered, in the context of photometric parallaxes found for HX Vel and other cluster members.Öğe Absolute parameters of young stars: V454 Carinae(Oxford Univ Press, 2019) Butland, R. J.; Erdem, A.; Ozkardes, B.; Blackford, M. G.; Surgit, D.; Budding, E.; Demircan, O.We present combined photometric and spectroscopic analyses of the multiple star V454 Carinae. High-resolution spectra of the system were taken at the University of Canterbury Mt. John Observatory during the years 2008-18. These have been processed using generic and purpose-built software. New digital single lens reflex photometry of the system has also been collected and similarly analysed. Absolute parameters for the three main stars confirm V454 Car's young and near-Main-Sequence nature. We find: M-1 = 4.6 +/- 0.4, M-2 = 4.4 +/- 0.4, M-3 = 4.5 +/- 0.5, R-1 = 2.83 +/- 0.18, R-2 = 2.74 +/- 0.16, R-3 = 2.78 +/- 0.16 (circle dot); T-1 similar to 17 500, T-2 similar to 15 500, T-3 similar to 15 000 (K), age similar to 30 Myr, photometric distance similar to 500 (pc). The major component V454 Car A is the close binary identified by the HIPPARCOS satellite. This binary and component B appear to be in eccentric orbits about a common centre of gravity with a period of similar to 1900 d. Analysis of the radial velocity curves suggests that the mass of component B is greater than that of its visible member. Measured radial velocities of this visible star show irregularities with a time-scale of about a week. The galactic location, proper motions, and age of V454 Car support the runaway nature proposed by others, and the combined results are consistent with a dynamical ejection scenario from the Vela region of Gould's Belt relatively soon after the stars' formation.Öğe Analysis of ? Librae including Hipparcos astrometry(Blackwell Publishing, 2006) Bakis, V.; Budding, E.; Erdem, A.; Bakis, H.; Demircan, O.; Hadrava, P.New spectroscopy of the classical Algol system delta Lib, combined with high-quality optical and infrared photometry, provides the basis for a good understanding of the close binary system's main parameters. Detailed analysis of the photometry reveals the significant role of a third light source, pointing to the existence of a companion to the eclipsing system of mass similar to 1 M-circle dot. We review the methodology of applying high-accuracy positional information, available from the Hipparcos Intermediate Astrometric Data archive, to stars that may have such companions. Analysis of the astrometry of delta Lib also points to a third star similar to the one already identified by Worek from radial-velocity data, although with slightly revised parameters. O-C data do not contradict this, but their general precision (while confirming the close pair's Algol status) fails to allow a decision on the third orbit parameters: Worek's or revised ones. Taking the photometry, spectroscopy and astrometry together, however, the existence of a third star of comparable mass to the Sun, as a relatively close companion to the eclipsing binary (similar to 4 au), is confirmed.Öğe Analysis of Exoplanet Light Curves(Astronomical Soc Pacific, 2015) Erdem, A.; Budding, E.; Rhodes, M. D.; Puskullu, Q.; Soydugan, Faruk; Soydugan, Esin; Tuysuz, M.We have applied the close binary system analysis package WINFITTER to a variety of exoplanet transiting light curves taken both from the NASA Exoplanet Archive and our own groundbased observations. WINFITTER has parameter options for a realistic physical model, including gravity brightening and structural parameters derived from Kopal's applications of the relevant Radau equation, and it includes appropriate tests for determinacy and adequacy of its best fitting parameter sets. We discuss a number of issues related to empirical checking of models for stellar limb darkening, surface maculation, Doppler beaming, microvariability, and transit time variation (TTV) effects. The Radau coefficients used in the light curve modeling, in principle, allow structural models of the component stars to be tested.Öğe Analysis of the exoplanet containing system Kepler-91(Springer, 2016) Budding, E.; Puskullu, C.; Rhodes, M. D.; Demircan, O.; Erdem, A.We have applied the graphical user interfaced close binary system analysis program WINFITTER to an intensive study of Kepler-91 using all the available photometry from the NASA Exoplanet Archive (NEA) at the Caltech website: http://exoplanetarchive.ipac.caltech.edu. Our fitting function for the tidal distortion derives from the relevant Radau equation and includes terms up to the fifth power of the fractional radius. This results in a systematic improvement in the mass ratio estimation over that of Lillo-Box et al. (Astron. Astrophys. 562:A109, 2014a) and our derived value for the mass ratio is in close agreement with that inferred from recent high-resolution spectroscopic data. It is clear that the data analysis in terms of simply an eclipsing binary system is compromised by the presence of significant other causes of light variation, in particular non-radial pulsations. We apply a low-frequency filtering procedure to separate out some of this additional light variation. Whilst the derived eccentricity appears then reduced, an eccentric effect remains in the light curve. We consider how this may be maintained in spite of likely frictional effects operating over a long time. There are also indications that could be associated with Trojan or other period-resonant mass concentrations. Suggestions of a possible secular period variation are briefly discussed.Öğe Apsidal Motion in Eclipsing Binaries: FT Ori and MZ Lac(Amer Inst Physics, 2016) Bulut, A.; Bulut, I.; Cicek, C.; Erdem, A.In this study, the apsidal motion analysis of two eccentric eclipsing binaries, FT Ori (P = 3.150 days, e = 0.397) and MZ Lac (P = 3.158 days, e = 0.399), have been presented. Their O - C diagrams were studied using all reliable times of minima found in the literature and new values for the elements of the apsidal motion for two systems have been computed. We found long periods of apsidal motion of 538 +/- 12 years and 424 +/- 6 years for FT Ori and MZ Lac, respectively.Öğe Apsidal Motion of Two Eclipsing Binaries: V796 Cyg and V2783 Ori(Amer Inst Physics, 2017) Bulut, A.; Bulut, I.; Cicek, C.; Erdem, A.In this study, the orbital period variations of two eclipsing binary systems showing apsidal motion were studied. Their O - C diagrams were analysed using all reliable eclipse timings and the elements of apsidal motion of two systems were improved. We found periods of apsidal motion of V796 Cyg and V2783 Ori to be 32.7 +/- 0.2 years and 415 +/- 50 years, respectively.Öğe CCD times of minima of some eclipsing variables(Hungarian Academy of Sciences (Konkoly Observatory), 2011) Doğru, S.S.; Erdem, A.; Aliçavuş, F.; Akin, T.; Kanvermez, C.[No abstract available]Öğe Collaborative Studies of Southern Close Binary Systems(Astronomical Soc Pacific, 2015) Budding, E.; Blackford, M.; Butland, R.; Demircan, O.; Erdem, A.; Idaczyk, R.; Ozkardes, B.We present a few items from our southern eclipsing binary program, underway in recent years and involving observations at the Mt. John University Observatory and elsewhere in Australasia. Reduction and analysis have also been carried out at COMU (Turkey). Derived parameters allow interesting comparisons with other recent findings on binary stars, observational and theoretical.Öğe Cool Active Binaries Recently Studied in the CAAM Stellar Program(Astronomical Soc Pacific, 2010) Cicek, C.; Erdem, A.; Soydugan, Faruk; Dogru, D.; Ozkardes, B.; Erkan, N.; Budding, E.We summarize recent work on cool active stars in our programme. We carried out photometry at the canakkale Onsekiz Mart University (COMU) observatory, and high-resolution spectroscopy at Mt John University Observatory, as well as collecting data from other facilties. A combination of analysis methods, including our information limit optimization technique (ILOT) with physically realistic fitting functions, as well as other public-domain software packages, have been used to find reliable parameters. Stars in our recent programme include V1430 Aql, VI 034 Her, V340 Gem, SAO 62042, FI Cnc, V2075 Cyg, FG UMa and BM CVn. Light variations, sometimes over numerous consecutive cycles, were analysed. For AB Dor and CF Tuc, we compared broadband (B and V) maculation effects with emission features in the Ca II K and H-alpha lines. Broadband light curves typically show one or two outstanding maculae. These appear correlated with the main chromospheric activity sites ('faculae'), that occur at similar latitudes and with comparable size to the photometric umbrae, but sometimes with significant displacements in longitude. The possibility of large-scale bipolar surface structure is considered, keeping in mind solar analogies. Such optical work forms part of broader multiwavelength studies, involving X-ray and microwave observations, also mentioned.Öğe Discovery of new variable stars at the Canakkale Onsekiz Mart University Observatory(Astronomical Soc Pacific, 2007) Bakis, V.; Bakis, H.; Demircan, O.; Budding, E.; Erdem, A.; Cicek, C.We present the light curves of five variable stars discovered at the Canakkale Onsekiz Mart University Observatory. From the light curve shapes of the variables we see that GSC 4288 0186 and GSC 4019 3345 are detached, USNO 1500-00409928 is a W UMa-type eclipsing binary, while the others seem to be intrinsic variable stars. By using a 30-cm telescope equipped with an ST237 CCD camera dedicated for times of minima observations, we plan to perform systematic observations to discover new variable stars with the help of automatic data reduction techniques in the future.Öğe Early-type W UMa contact binary system: New data on V535 Ara(Elsevier Science Bv, 2012) Ozkardes, B.; Erdem, A.This paper presents the results of spectroscopic and photometric observations of the early-type W UMa system V535 Ara. New high-resolution spectra were taken at the Mt. John University Observatory in 2007. Radial velocities and spectroscopic orbital elements of the system were determined by applying KOREL spectral disentangling. The resulting orbital elements were: a(1)sini = 0.0047 +/- 0.0001 AU, a(2)sini = 0.0146 +/- 0.0001 AU, M(1)sin(3)i = 1.85 +/- 0.01 M(circle dot), and M(2)sin(3)i = 0.59 +/- 0.01 M(circle dot). The components were found to be in synchronous rotation following examination of their disentangled H gamma line profiles. Four photometric data-sets (1966 BV, 1967 BV, HIPPARCOS and ASAS) were modeled using the Wilson-Devinney method. The model describes V535 Ara as an A sub-type W UMa type eclipsing binary which has a fill out factor of 0.22 in marginal contact configuration. The simultaneous solution of light and radial velocity curves gave the following absolute parameters: M(1) = 1.94 +/- 0.04 M(circle dot), M(2) = 0.59 +/- 0.02 M(circle dot), R(1) = 2.09 +/- 0.03 R(circle dot), R(2) = 1.23 +/- 0.02R(circle dot), L(1) = 18 +/- 3 L(circle dot), and L(2) = 6 +/- 1 L(circle dot). The distance to V535 Ara was calculated as 123 20 pc using distance modulus with correction for interstellar extinction. (C) 2011 Elsevier B.V. All rights reserved.
