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Double-lined Spectroscopic Binary Stars in the Radial Velocity Experiment Survey
We devise a new method for the detection of double-lined binary stars ina sample of the Radial Velocity Experiment (RAVE) survey spectra. Themethod is both tested against extensive simulations based on syntheticspectra and compared to direct visual inspection of all RAVE spectra. Itis based on the properties and shape of the cross-correlation function,and is able to recover ~80% of all binaries with an orbital period oforder 1 day. Systems with periods up to 1 yr are still within thedetection reach. We have applied the method to 25,850 spectra of theRAVE second data release and found 123 double-lined binary candidates,only eight of which are already marked as binaries in the SIMBADdatabase. Among the candidates, there are seven that show spectralfeatures consistent with the RS CVn type (solar type with activechromosphere) and seven that might be of W UMa type (over-contactbinaries). One star, HD 101167, seems to be a triple system composed ofthree nearly identical G-type dwarfs. The tested classification methodcould also be applicable to the data of the upcoming Gaia mission.
| New absolute magnitude calibrations for W Ursa Majoris type binaries
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed.31 W UMa stars, which have the most accurate parallaxes(σπ/π<0.15) which are neither associated with aphotometric tertiary nor with evidence of a visual companion, wereselected for re-calibrating the Period-Luminosity-Color (PLC) relationof W UMa stars. Using the Lutz-Kelker (LK) bias corrected (mostprobable) parallaxes, periods ({0.26< P< 0.87}, P in days), andcolors ({0.04<(B-V)0<1.28}) of the 31 selected W UMa,the PLC relation have been revised and re-calibrated. The differencebetween the old (revised but not bias corrected) and the new (LK biascorrected) relations are almost negligible in predicting the distancesof W UMa stars up to about 100 pc. But, it increases and may becomeintolerable as distances of stars increase. Additionally, using(J-H)0 and (H-K_s)0 colors from 2MASS (Two MicronAll Sky Survey) data, a PLC relation working with infrared data wasderived. It can be used with infrared colors in the range-0.01<(J-H)0<0.58, and{-0.10<(H-K_s)0<0.18}. Despite of the fact that the2MASS data refer to single epoch observations which are not guaranteedto be taken at maximum brightness of the W UMa stars, the establishedrelation has been found surprisingly consistent and reliable inpredicting LK corrected distances of W UMa stars.
| The evolutionary status of W Ursae Majoris-type systems
Well-determined physical parameters of 130 W Ursae Majoris (W UMa)systems were collected from the literature. Based on these data, theevolutionary status and dynamical evolution of W UMa systems areinvestigated. It is found that there is no evolutionary differencebetween W- and A-type systems in the M-J diagram, which is consistentwith the results derived from the analysis of observed spectral type andof M-R and M-L diagrams of W UMa systems. M-R and M-L diagrams of W- andA-type systems indicate that a large amount of energy should betransferred from the more massive to the less massive component, so thatthey are not in thermal equilibrium and undergo thermal relaxationoscillation. Moreover, the distribution of angular momentum, togetherwith the distribution of the mass ratio, suggests that the mass ratio ofthe observed W UMa systems decreases with decreasing total mass. Thiscould be the result of the dynamical evolution of W UMa systems, whichsuffer angular momentum loss and mass loss as a result of the magneticstellar wind. Consequently, the tidal instability forces these systemstowards lower q values and finally to rapidly rotating single stars.
| VSOP: the variable star one-shot project. I. Project presentation and first data release
Context: About 500 new variable stars enter the General Catalogue ofVariable Stars (GCVS) every year. Most of them however lackspectroscopic observations, which remains critical for a correctassignement of the variability type and for the understanding of theobject. Aims: The Variable Star One-shot Project (VSOP) is aimed at (1)providing the variability type and spectral type of all unstudiedvariable stars, (2) process, publish, and make the data available asautomatically as possible, and (3) generate serendipitous discoveries.This first paper describes the project itself, the acquisition of thedata, the dataflow, the spectroscopic analysis and the on-lineavailability of the fully calibrated and reduced data. We also presentthe results on the 221 stars observed during the first semester of theproject. Methods: We used the high-resolution echelle spectrographsHARPS and FEROS in the ESO La Silla Observatory (Chile) to survey knownvariable stars. Once reduced by the dedicated pipelines, the radialvelocities are determined from cross correlation with synthetic templatespectra, and the spectral types are determined by an automatic minimumdistance matching to synthetic spectra, with traditional manual spectraltyping cross-checks. The variability types are determined by manuallyevaluating the available light curves and the spectroscopy. In thefuture, a new automatic classifier, currently being developed by membersof the VSOP team, based on these spectroscopic data and on thephotometric classifier developed for the COROT and Gaia space missions,will be used. Results: We confirm or revise spectral types of 221variable stars from the GCVS. We identify 26 previously unknown multiplesystems, among them several visual binaries with spectroscopic binaryindividual components. We present new individual results for themultiple systems V349 Vel and BCGru, for the composite spectrum star V4385Sgr, for the T Tauri star V1045 Sco, andfor DM Boo which we re-classify as a BY Draconisvariable. The complete data release can be accessed via the VSOP website.Based on data obtained at the La Silla Observatory, European SouthernObservatory, under program ID 077.D-0085.
| Physical parameters and multiplicity of five southern close eclipsing binaries
Aims.We detected tertiary components of close binaries from spectroscopyand light curve modelling, investigated the light-travel time effect andthe possibility of magnetic activity cycles, measured mass ratios forunstudied systems, and derived absolute parameters. Methods: We carriedout new photometric and spectroscopic observations of five bright (< 10.5 mag) close eclipsing binaries, predominantly in thesouthern skies. We obtained full Johnson BV light curves, which weremodelled with the Wilson-Devinney code. Radial velocities were measuredwith the cross-correlation method using IAU radial velocity standards asspectral templates. Period changes were studied with the O-C method,utilising published epochs of minimum light (XY Leo) and ASAS photometry(VZ Lib). Results: For three objects (DX Tuc, QY Hya, V870 Ara),absolute parameters have been determined for the first time. Wespectroscopically detected the tertiary components in XY Leo and VZ Liband discovered one in QY Hya. For XY Leo we updated the light-timeeffect parameters and detected a secondary periodicity of about 5100 din the O-C diagram that may hint at the existence of short-periodmagnetic cycles. A combination of recent photometric data shows that theorbital period of the tertiary star in VZ Lib is likely to be over 1500d. QY Hya is a semi-detached X-ray active binary in a triple system withK and M-type components, while V870 Ara is a contact binary with thethird smallest spectroscopic mass ratio for a W UMa star to date (q =0.082 ± 0.030). Being close to the theoretical minimum forcontact binaries, this small mass ratio suggests that V870 Ara has thepotential of constraining evolutionary scenarios of binary mergers. Theinferred distances to these systems are compatible with the Hipparcosparallaxes.Based on observations made at the Siding Spring Observatory, Australia.Light curves and radial velocity data are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/943
| 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.
| 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.
| 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.
| Catalogue of the field contact binary stars
A catalogue of 361 galactic contact binaries is presented. Listedcontact binaries are divided into five groups according to the type andquality of the available observations and parameters. For all systemsthe ephemeris for the primary minimum, minimum and maximum visualbrightness and equatorial coordinates are given. If available,photometric elements, (m1+m2)sin3i,spectral type, parallax and magnitude of the O'Connell effect are alsogiven. Photometric data for several systems are augmented by newobservations. The quality of the available data is assessed and systemsrequiring modern light-curve solutions are selected. Selectedstatistical properties of the collected data are discussed.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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Osservazione e dati astrometrici
| Costellazione: | Tucano |
| Ascensione retta: | 23h57m21.52s |
| Declinazione: | -64°14'35.6" |
| Magnitudine apparente: | 9.613 |
| Moto proprio RA: | 9.6 |
| Moto proprio Dec: | -44 |
| B-T magnitude: | 10.237 |
| V-T magnitude: | 9.665 |
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