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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 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 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 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 Detection of a cyclic period change in the contact binary TU UMi(Slovak Academy Sciences Astronomical Inst, 2022) Camurdan, D. Zengin; Ozkardes, B.This study aims at timing the eclipses of the binary star TU UMi. The times of minima are taken from the literature, from our observations in April 2004 and from TESS observations between 2019 and 2022. The orbital period analysis of the system indicates that there is a cyclic oscillation with an amplitude of 0.0081d and a period of 9.03 yr, accompanied by a continuous decrease at a rate of dP/dt = ???1.12 ?? 10???7 d yr???1. We study the secular evolution of the orbital period of the system and the possibility of the existence of a third companion or the magnetic activity cycle of the primary component in the system.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.Öğe First Spectroscopic Study of the Southern Eclipsing Binary V454 Carina(Astronomical Soc Pacific, 2015) Ozkardes, B.; Erdem, A.; Surgit, D.; Butland, R.; Budding, E.We present preliminary results from the analysis of spectroscopic observations of the southern eclipsing binary star V454 Car (HIP 36682). High-resolution spectra of the system were taken at the Mt. John University Observatory in 2009, 2010, 2011, and 2014. Detailed examination of the spectra indicates that V454 Car is a triple system. Radial velocities of the components of the eclipsing pair were obtained. The orbital solution gave quite a large spectroscopic mass ratio of q(spec) = 0.93 +/- 0.05.Öğe Light Curve Analysis Of Beta Lyrae Type Binary Star EM TrA(Amer Inst Physics, 2017) Ozkardes, B.An analysis of photometric observations of the eclipsing binary system EM TrA (TYC 9258-211-1=CD-67 1660) is presented in this study. The V light curve of the system from All Sky Automated Survey (ASAS) was solved using the Wilson-Devinney code. The final solution describes EM TrA as a detached system. The absolute parameters of the components of the system were estimated.Öğe Orbital Parameters Of The Multiple System EM Boo(Amer Inst Physics, 2018) Ozkardes, B.; Bakis, H.; Bakis, V.EM Boo is a relatively bright (V = 8.98 mag.) and short orbital period (P similar to 2.45 days) binary star member of the multiple system WDS J14485+2445AB. There is neither photometric nor spectroscopic study of the system in the literature. In this work, we obtained spectroscopic orbital parameters of the system from new high resolution spectroscopic observations made with echelle spectrograph attached to UBT60 telescope of Akdeniz University. The spectroscopic solution yielded the values K-1 = 100.7 +/- 2.6 km/s, K-2 = 120.1 +/- 2.6 km/s and V-gamma = -14.6 +/- 3.1 km/s, and thus the mass ratio of the system q = 0.838 +/- 0.064.Öğe Photometric analysis of the contact binary star V829 Hercules using light curves on three consecutive years(Elsevier Science Bv, 2006) Erdem, A.; Ozkardes, B.New BVR light curves and photometric analysis of the contact binary star V829 Her are presented. The light curves were obtained at the COMU Observatory in the consecutive years 2003, 2004 and 2005. Firstly, the variation of the orbital period of the system was studied. The sinusoidal and secular changes were found and examined in terms of two plausible mechanisms, namely (i) the conservative mass transfer between the components of the system and (ii) the light-time effect due to an unseen component in the system. The instrumental magnitudes of all observed stars in this study were converted into standard magnitudes. We also study nature of asymmetries and the intrinsic variability in the light curves of the system. Light variations are summarized: (a) changes of light levels of both maxima and (b) changes of the depths of both primary and secondary eclipses. These peculiar asymmetries were interpreted in terms of dark spot(s) on the surface of the large and more massive component star. The present BVR light curves and radial velocity curves obtained by Lu, W., Rucinski, S. M., 1999. AJ It 8, 515 were analysed by means of the latest version of the Wilson-Devinney program, simultaneously. Thus, the absolute parameters of the system were also derived. (c) 2006 Elsevier B.V. All rights reserved.Öğe Photometric analysis of the contact binary star V842 Hercules on the basis of seasonal light curves(Elsevier Science Bv, 2009) Erdem, A.; Ozkardes, B.We present new BVR light curves and photometric analysis of the contact binary star V842 Her. The light curves were obtained at the COMU Observatory in the consecutive years 2003, 2004. 2005, and also 2007. We studied the variation of the orbital period of the system. The O-C diagram shows a quasi-sinusoidal form superimposed on a parabola. The parabolic variation, which indicates the secular increase of the orbital period of the system, was interpreted in terms of the combined effect of mass transfer between the components of the system and mass loss by a stellar wind from the system. The sinusoidal form of the orbital period variation was considered as an apparent change and interpreted in term of the light-time effect due to an unseen component in the system. Vie have also studied the nature of asymmetries and the intrinsic variability in the light curves of the system. The differences between light levels of both maxima (i.e. O'Connell effect) and minima are changing with time. These peculiar asymmetries were explained by a dark spot on the surface of the large and more massive component star. The present BVR light curves and radial velocity curves obtained by [Rucinski, S.M., Lu, W., 1999. AJ 118, 2451] were analysed by means of the Wilson-Devinney method supplemented with a Monte Carlo type algorithm. Absolute parameters of the system were also derived. They are m(1) = 0.38 m(circle dot), m(2) = 1.45 m(circle dot), R(1) = 0.81 R(circle dot), R(2) = 1.47 R(circle dot), M(V,1) = 5(m).08 and M(V,2) = 4(m).06. (C) 2008 Elsevier B.V. All rights reserved.Öğe Photometric analysis of the contact binary system V829 hercules(Astronomical Soc Pacific, 2007) Ozkardes, B.; Erdem, A.New BV R light curves and photometric analysis of the contact binary star V829 Her are presented. The light curves were obtained at the Canakkale Onsekiz Mart University Observatory in 2005. All the times of minimum light were collected and combined with the new ones presented in this work. The variation of the orbital period of the system was then analysed. Sinusoidal and secular changes were found. These variations were examined in terms of two plausible mechanisms, namely (i) mass transfer, and (ii) a light-time effect due to an unseen component in the system. The instrumental differential magnitudes of the system were converted into standard magnitudes. So, we calculate BV R standard magnitudes of the system and obtain the mean color indices of B - V = 0.59 +/- 0.01 for V829 Her, which indicates the spectral type of the system to be G0-1. The light curves are generally those of contact binaries, but there are large asymmetries between maxima. New BV R light curves and radial velocity curves available from the literature were analysed, simultaneously. Light curve asymmetries of the system were explained in terms of a large dark starspot on the more massive component. Absolute parameters of the system were also derived.Öğe Photometric Study of The Eclipsing Binary ET Psc(Amer Inst Physics, 2016) Ozalp, G. Z.; Ozkardes, B.We present the photometric solution of the eclipsing binary ET Psc (GSC 00608-00490). The ASAS V-band photometric data of the system was modelled using the Wilson-Devinney method. The result shows that the eclipsing pair could be classified as A-subtype of W UMa-type binary system. The absolute dimensions of the system were also estimated based on the photometric solution.Öğe Physical parameters of neglected southern eclipsing binary IL Lib(Elsevier Science Bv, 2017) Ozkardes, B.This paper presents results from the combined analysis of light curve (from the All Sky Automated Survey) and radial velocity curves (from Nordstrom et al., 1997) of the eclipsing binary IL Lib. The final solution describes the system as a detached binary. Absolute parameters of this southern detached binary were calculated as follows: M1 = 1.49 +/- 0.12 M-circle dot, M-2 = 1.31 +/- 0.14 M-circle dot, R-1 = 1.52 +/- 0.23 R-circle dot, R-2 = 1.52 +/- 0.23 R-circle dot, L-1 = 4.99 +/- 2.07 L-circle dot and L-2 = 3.65 +/- 1.55 L-circle dot. The distance to IL Lib was computed as 103 +/- 20 pc using the distance modulus with corrections for interstellar extinction. The positions of the components of IL Lib in the HR diagram are also discussed. (C) 2017 Elsevier B.V. All rights reserved.
