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Properties and nature of Be stars. XXI. The long-term and the orbital variations of V832 Cyg = 59 Cyg
An analysis of numerous homogenized UBV photoelectric observations andred spectra of the Be star V832 Cyg from several observatories led tothe following principal findings: 1. Pronounced long-term light andcolour variations of V832 Cyg result from a combination of two effects:from the gradual formation of a new Be envelope, and from an asymmetryand a slow revolution of the envelope (or its one-armed oscillation).The colour variations associated with the envelope formation arecharacterized by a positive correlation between brightness and emissionstrength, typical for stars which are not seen roughly equator-on. 2.The V magnitude observations prewhitened for the long-term changesfollow a sinusoidal orbital light curve with a small amplitude and aperiod of 28.1971d which is derived from observations spanning 43 years.This independently confirms a 12-year old suggestion that the star is aspectroscopic binary with a 29-d period. V832 Cyg thus becomes the fifthknown Be star with cyclic long-term V/R variations, the duplicity ofwhich has been proven, the four other cases being ζ Tau, V923 Aql,γ Cas and X Per. Therefore, the hypothesis that the long-term V/Rvariations may arise due to the attractive force of the binary companionat certain phases of the envelope formation is still worth consideringas a viable alternative to the model of one-armed oscillation. 3. Wehave shown that the RV and V/R variations of the Hα and He I 6678emission lines are all roughly in phase. In particular, the He I 6678emission also moves with the Be primary which differs from what wasfound for another Be binary, \varphi Per. 4. We derived the orbitalelements and found that in spite of the remaining uncertainties, thebasic physical properties of the 28.2d binary are well constrained. 5.The light minimum of the orbital light curve occurs at elongation whenthe Be star is approaching us and the object becomes bluest in (B-V) andreddest in (U-B) at the same time. This may indicate that a part of theoptically thick regions of the envelope is eclipsed at these orbitalphases. Guest investigator, Dominion Astrophysical Observatory, HerzbergInstitute of Astrophysics, National Research Council of Canada. Alsobased on observations from Castanet-Tolosan, Hvar, Ondřejov,Pic-du-Midi, Rozen, San Pedro Mártir, Toronto and Xing-LongObservatories and on photoelectric photometry by AAVSO members. Tables3, 5-7 are only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/580}
| Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations
Radial motions of stars in nearby moving clusters are determined fromaccurate proper motions and trigonometric parallaxes, without any use ofspectroscopy. Assuming that cluster members share the same velocityvector (apart from a random dispersion), we apply a maximum-likelihoodmethod on astrometric data from Hipparcos to compute radial and spacevelocities (and their dispersions) in the Ursa Major, Hyades, ComaBerenices, Pleiades, and Praesepe clusters, and for theScorpius-Centaurus, alpha Persei, and ``HIP 98321'' associations. Theradial motion of the Hyades cluster is determined to within 0.4 kms-1 (standard error), and that of its individual stars towithin 0.6 km s-1. For other clusters, Hipparcos data yieldastrometric radial velocities with typical accuracies of a few kms-1. A comparison of these astrometric values withspectroscopic radial velocities in the literature shows a good generalagreement and, in the case of the best-determined Hyades cluster, alsopermits searches for subtle astrophysical differences, such as evidencefor enhanced convective blueshifts of F-dwarf spectra, and decreasedgravitational redshifts in giants. Similar comparisons for the ScorpiusOB2 complex indicate some expansion of its associations, albeit slowerthan expected from their ages. As a by-product from the radial-velocitysolutions, kinematically improved parallaxes for individual stars areobtained, enabling Hertzsprung-Russell diagrams with unprecedentedaccuracy in luminosity. For the Hyades (parallax accuracy 0.3 mas), itsmain sequence resembles a thin line, possibly with wiggles in it.Although this main sequence has underpopulated regions at certaincolours (previously suggested to be ``Böhm-Vitense gaps''), suchare not visible for other clusters, and are probably spurious. Futurespace astrometry missions carry a great potential for absoluteradial-velocity determinations, insensitive to the complexities ofstellar spectra. Based on observations by the ESA Hipparcos satellite.Extended versions of Tables \ref{tab1} and \ref{tab2} are available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.125.8) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/446
| A Search for Star Clusters from the HIPPARCOS Data
We present results of a search for nearby star clusters and associationsusing Hipparcos Catalogue data, restricting the sample to stars withparallaxes above 2 mas (d <~ 500 pc). Two new OB associations havebeen identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecularegions. A very probable new open cluster has been discovered in Carina.The cluster, a Car, named after its brightest member, is young (60 Myr)and nearby (d = 132 pc). However, only seven bona fide members can bedrawn from the Hipparcos data. We report a detection of nine opencluster candidates in the distance range of 150 to 400 pc, and sixpossible associations almost all located within the Gould belt, althoughslightly older than the known nearby associations. In all cases, wepresent Yale theoretical isochrone fits to the color-magnitude diagrams,which indicate a moderate spread of ages between 60 to 200 Myr.Evidently, these young open cluster and association candidates arerelated to the overall distribution of young OB and A-type stars in thesolar neighborhood.
| 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.
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| Observations of interstellar diffuse absorption band at 4430 A
Observations of the interstellar diffuse absorption band at 4430 A for800 O and B stars in Neckel's (1967) catalog are being carried out, and482 spectra obtained up to September 1983 have been reduced. It isconfirmed that the strength of the interstellar diffuse absorption bandat 4430 A does not simply relate to the abundance of interstellar grainson the line of sight. The relation between the color excess E(B-V) andthe equivalent width of the band to the direction of l = 130-140 deg andb = -5 to +5 deg shows that some parameter(s) other than E(B-V) is (are)needed to understand the cause of this band.
| Catalogue d'etoiles O et B.
Not Available
| Etude pour chaque champ de l'absorption et de la repartition des vitesses radiales EN fonction de la distance.
Not Available
| The Light-Variability of Early B Giants.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..577L&db_key=AST
| Mesures de vitesses radiales au spectrographe C de l'Observatoire de Haute Provence
Not Available
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