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Physical parameters of some close binaries: ET Boo, V1123 Tau, V1191 Cyg, V1073 Cyg and V357 Peg
With the aim of providing new and up-to-date absolute parameters of someclose binary systems, new BVR CCD photometry was carried out at theAnkara University Observatory (AUG) for five eclipsing binaries, ET Boo,V1123 Tau, V1191 Cyg, V1073 Cyg and V357 Peg between April, 2007 andOctober, 2008. In this paper, we present the orbital solutions for thesesystems obtained by simultaneous light and radial velocity curveanalyses. Extensive orbital solution and absolute parameters for ET Boosystem were given for the first time through this study. According tothe analyses, ET Boo is a detached binary while the parameters of fourremaining systems are consistent with the nature of contact binaries.The evolutionary status of the components of these systems are alsodiscussed by referring to their absolute parameters found in this study.
| Absolute parameters and physical nature of two W-UMa type binaries: V1123 Tau and V1128 Tau
We present high-precision, multi-band CCD photometry of two less-studiedclose binaries V1123 Tau and V1128 Tau. Complete covered light curvesand a number of new times of light minima of the two eclipsing systemswere obtained, based on which, revised orbital elements and newephemerides were given. By adopting the Wilson-Devinney method, thelight curves were analyzed. The photometric solutions confirm the WUMa-type nature of the binary systems. With the less-massive secondaryslightly cooler than the primary, V1123 Tau could be classified as anA-type contact system. While V1128 Tau is typically considered a W-typeW UMa star, the surface temperature of its secondary component isdetermined to be absolutely higher than the primary by about 270 K.Combining with the results of radial-velocity solutions, we determinedabsolute parameters of the two systems. The mass, radius and luminosityfor each component of V1123 Tau were derived as: 1.36 ±0.05M&sun;, 1.37 ± 0.02R&sun;, and 2.01± 0.07L&sun; and 0.40 ± 0.02M&sun;,0.80 ± 0.01R&sun;, and 0.67 ±0.04L&sun;, respectively. For V1128 Tau, the absoluteparameters were computed to be 1.09 ± 0.03M&sun;, 1.01± 0.01R&sun;, and 1.34 ± 0.06L&sun;and 0.58 ± 0.01M&sun;, 0.76 ±0.01R&sun;, and 0.91 ± 0.05L&sun;,respectively. Based on these results, the evolutionary status and thephysical nature of the two binary systems are discussed, while alsoconnecting with the theoretical models.
| Physical parameters of 62 eclipsing binary stars using the All Sky Automated Survey-3 data - I
We present a detailed light-curve analysis of publicly available V-bandobservations of 62 binary stars, mostly contact binaries, obtained bythe All Sky Automated Survey (ASAS)-3 project between 2000 and 2009.Eclipsing binaries are important astronomical targets for determiningthe physical parameters of component stars from the geometry of theirorbits. They provide an independent direct method of measuring the radiiof stars. We improved the ASAS determined periods and ephemerides, andobtained the Fourier parameters from the phased light curves of these 62stars. These Fourier parameters were used for preliminary classificationof the stars in our sample. The phased light curves were then analysedwith the aid of the Wilson-Devinney light-curve modelling technique inorder to obtain various geometrical and physical parameters of thesebinaries. The spectroscopic mass ratios as determined from the radialvelocity measurements available in the literature were used as one ofthe inputs to the light-curve modelling. Thus reliable estimations ofparameters of these binaries were obtained with combined photometric andspectroscopic data, and error estimates were made using the heuristicscan method. For several systems in the sample, the solutions wereobtained for the first time and would serve as a good source in thefuture for light-curve analysis based on more precise follow-up CCDphotometric observations. Out of 62 stars in the sample, photometricanalysis of 39 stars is presented here for the first time using the ASASphotometry and precise spectroscopic mass ratios. From the analysis, wefound 54 contact binaries, six semidetached binaries and two detachedbinaries. The Fourier parameters in the a2-a4plane were used for preliminary classification, and the finalclassification was done based on the Roche lobe geometry obtained fromthe light-curve modelling.
| BAV-Results of Observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
Not Available
| Absolute dimensions of solar-type eclipsing binaries. II. V636 Centauri: A 1.05 {M}ȯ primary with an active, cool, oversize 0.85 {M}ȯ secondary
Context: The influence of stellar activity on the fundamental propertiesof stars around and below 1 Mȯ is not well understood.Accurate mass, radius, and abundance determinations from solar-typebinaries exhibiting various levels of activity are needed for a betterinsight into the structure and evolution of these stars. Aims: Weaim to determine absolute dimensions and abundances for the solar-typedetached eclipsing binary V636 Cen, and to perform a detailed comparisonwith results from recent stellar evolutionary models. Methods:uvby light curves and uvbyβ standard photometry were obtained withthe Strömgren Automatic Telescope, radial velocity observationswith the CORAVEL spectrometer, and high-resolution spectra with theFEROS spectrograph, all at ESO, La Silla. State-of-the-art methods wereapplied for the photometric and spectroscopic analyses. Results:Masses and radii that are precise to 0.5% have been established for thecomponents of V636 Cen. The 0.85 Mȯ secondary componentis moderately active with starspots and Ca ii H and K emission, and the1.05 Mȯ primary shows signs of activity as well, but ata much lower level. We derive a [Fe/H] abundance of -0.20 ± 0.08and similar abundances for Si, Ca, Ti, V, Cr, Co, and Ni. Correspondingsolar-scaled stellar models are unable to reproduce V636 Cen, especiallyits secondary component, which is ~10% larger and ~400 K cooler thanpredicted. Models adopting significantly lower mixing-length parametersl/Hp remove these discrepancies, seen also for othersolar-type binary components. For the observed [Fe/H], Claret models forl/Hp = 1.4 (primary) and 1.0 (secondary) reproduce thecomponents of V636 Cen at a common age of 1.35 Gyr. The orbit iseccentric (e = 0.135 ± 0.001), and apsidal motion with a 40%relativistic contribution has been detected. The period is U = 5 270± 335 yr, and the inferred mean central density concentrationcoefficient, log(k_2) = -1.61 ± 0.05, agrees marginally withmodel predictions. The measured rotational velocities, 13.0 ± 0.2(primary) and 11.2 ± 0.5 (secondary) km s-1, are inremarkable agreement with the theoretically predicted pseudo-synchronousvelocities, but are about 15% lower than the periastron values. Conclusions: V636 Cen and 10 other well-studied inactive and activesolar-type binaries suggest that chromospheric activity, and its effecton envelope convection, is likely to cause radius and temperaturediscrepancies, which can be removed by adjusting the model mixing lengthparameters downwards. Noting this, the sample may also lend support totheoretical 2D radiation hydrodynamics studies, which predict a slightdecrease of the mixing length parameter with increasing temperature/massfor inactive main sequence stars. More binaries are, however, needed fora description/calibration in terms of physical parameters and level ofactivity.Based on observations carried out at the Strömgren AutomaticTelescope (SAT), the Danish 1.54 m telescope, and the 1.5 m telescope(62.L-0284) at ESO, La Silla, Chile. Table A.1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/253
| Optical spectroscopy of V1123 Tauri and its visual companion
We present long-slit intermediate resolution spectroscopy of the visualbinary V1123. We confirm that component A is a W UMa eclipsing star withspectral type G0V, while component B is a K0V. We infer a distance tothe system of 125 pc, and then a projected separation between bothcomponents of 520 AU. The difference in radial velocities of componentsA and B is ?20 km s-1. At the distance od thesystem, the flux measured by ROSAT for the component A, corresponds toan X-ray luminosity of Lx=30.23ergs which iswithin typical values for W UMa systems.
| Radial Velocity Studies of Close Binary Stars. XIII
Radial velocity (RV) measurements and sine-curve fits to the orbital RVvariations are presented for ten close binary systems: EG Cep, V1191Cyg, V1003 Her, BD+7°3142, V357 Peg, V407 Peg, V1123 Tau, V1128 Tau,HH UMa, and PY Vir. While most of the studied eclipsing systems arecontact binaries, EG Cep is a detached or a semidetached double-linedbinary and V1003 Her is a close binary of an uncertain type seen at avery low inclination angle. We discovered two previously unknown triplesystems, BD+7°3142 and PY Vir, both with late spectral-type (K2V)binaries. Of interest is the low mass-ratio (q = 0.106) close binaryV1191 Cyg showing an extremely fast period increase; the system has avery short period for its spectral type and shows a W-type light curve,a feature rather unexpected for such a low mass-ratio system.Based on the data obtained at the David Dunlap Observatory, Universityof Toronto.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple systems.
| The First Ground-Based Photometry of V1123 Tauri
Not Available
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Times of Minima for Neglected Eclipsing Binaries in 2004
Times of minima obtained during 2004 for a number of neglected eclipsingbinaries are presented.
| CCD Minima for Selected Eclipsing Binaries in 2004
Not Available
| Times of Minima for Some Eclipsing Binaries
Times of minima for a number of some eclipsing binaries are presented.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| Key parameters of W UMa-type contact binaries discovered by HIPPARCOS
A sample of W UMa-type binaries which were discovered by the HIPPARCOSsatellite was constructed with the aid of well defined selectioncriteria described in this work. The selection process showed up thatseveral systems of which the variability types have been assigned as EBin HIPPARCOS catalogue are genuine contact binaries of W UMa-type. Thelight curves of the 64 selected systems based on HIPPARCOS photometrywere analyzed with the aid of light curve synthesis method by Rucinskiand their geometric elements (namely mass ratio q, degree of contact f,and orbital inclination i) were determined. The solutions were obtainedfor the first time for many of the systems in the sample and would be agood source for their future light curve analyses based on more precisefollow-up observations.Based on observations made with the ESA HIPPARCOSastrometry satellite.
| Photoelectric Minimum Times of Some Eclipsing Binary Stars
We present 24 minimum times of 7 eclipsing binaries observed in theyears from 2001 to 2003.
| New Times of Minima of Eclipsing Binary Systems
We present several photoelectric minima observations of 7 eclipsingbinaries.
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