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Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| The BF Aurigae system. A close binary at the onset of mass transfer
Because the question of the mass ratio of the early-type system BF Aurhas not yet fully been clarified, we present and analyse new UBVphotometry and nearly contemporaneous radial velocity observations. Froma simultaneous least squares analysis of the photometric light curvesand the new radial velocity curves we derive a mass ratio of q=1.048+/-0.02. With even much more accurate photometric and spectroscopic datathe mass ratio remains weakly defined. The resulting stellar parametersare consistent with line ratios derived from old and our new spectra andavailable Strömgren indices. We confirm earlier conclusions that BFAur is detached and that the more massive component is almost fillingits Roche lobe. New data indicating a period change support theinterpretation that mass exchange has already started or is about tostart. Tables A1-A5 are available electronically only at the CDS viaanonymous ftp (130.79.128.5) ftp://cdsarc.u-strasbg.fr orhttp://cdsweb.u-strasbg.fr/index.htm
| A Model of the Early Type Binary System BF Aurigae
A physically consistent model is presented for the early-type eclipsingbinary system BF Aur, based on a simultaneous solution of its light andradial velocity curves. The less massive fainter (but hotter) secondaryis smaller but almost Roche lobe filling component. The system is thusnot reverse-algol. The absolute parameters of the system are found tobe: Mh=3.3 Modot, Mc= 4.1Modot, Th= 15600 K, Tc= 15400 K,Rh= 3.9 Rodot, Rc= 4.1Rodot. More accurate radial velocity data are needed beforeuniqueness can be claimed for the model.
| An Analysis of the Light Curves of the Early-Type Binary BF Aurigae
The UBV observations of the massive binary BF Aur were made at theAnkara University Observatory during 1988, 1989 and 1996. Asymmetry ofthe light curves, arising from unequal height of successive maxima,indicates that the system is active. By analysing these observations inthe framework of the Roche model (including the presence of brightregions on the components) one obtains a semidetached configuration ofthe system, with the cooler secondary component filling its Roche lobe.The analysis of the light curves yields consistent solutions for massratio q = m2/m1 somewhat less than one. Theinfluence of the mass transfer on the change of thesystem-orbital-period is relatively small. The upward paraboliccharacter of the O-C diagram (Zhang et al., 1993) indicates a masstransfer from the less massive secondary to the more massive primary.This inturn requires the less massive secondary to fill its Roche lobe.This is consistent with our solution. Based on these facts we introducedthe following working hypothesis. At the place where the gas stream fromthe secondary falls on the primary, relatively small in size but a hightemperature contrast active hot-spot (hs) region is formed. As a resultof the heating effect caused by the irradiation of the hot-spot region,on the secondary's side facing the hot spot a bright-spot (bs) region isformed. The bright-spot region is larger in size but with significantlylower temperature than the hot spot. This region can be treated as a`reflection cap'. By analysing the light curves in the framework of thisworking hypothesis the basic parameters of the system and the activeregions are estimated. The problem is solved in two stages: by obtaininga synthetic light curve in the case when the parameters of thecorresponding Close Binary (CB) Roche model (Djurašević,1992a) are given a priori (the direct problem) and by determining theparameters of the given model for which the best fit between thesynthetic light curve and the observations is achieved (the inverseproblem) (Djurašević, 1992b).
| UvbyHbeta_ photometry of main sequence A type stars.
We present Stroemgren uvby and Hbeta_ photometry for a set of575 northern main sequence A type stars, most of them belonging to theHipparcos Input Catalogue, with V from 5mag to 10mag and with knownradial velocities. These observations enlarge the catalogue we began tocompile some years ago to more than 1500 stars. Our catalogue includeskinematic and astrophysical data for each star. Our future goal is toperform an accurate analysis of the kinematical behaviour of these starsin the solar neighbourhood.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Etude pour chaque champ de l'absorption et de la repartition des vitesses radiales EN fonction de la distance.
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| La mesure des vitesses radiales au prisme objectif. VII - 2e liste de vitesses radiales déterminées au prisme objectif à vision directe
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