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| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Wind Inhomogeneities in Wolf-Rayet Stars. IV. Using Clumps to Probe the Wind Structure in the WC8 Star HD 192103
We present the most intensive, high-quality spectroscopic monitoring ofoptical Wolf-Rayet emission lines ever obtained. The Wolf-Rayet star HD192103 (=WR 135; subtype WC8) was observed in the 5650-5840 Åregime alternately from both the William Herschel Telescope and theCanada-France-Hawaii Telescope. The final data consist of a series of197 spectra spread over 64 hr, each with a resolving powerλ/Δλ~=20,000 and a signal-to-noise ratio in thecontinuum ~=450 per 3 pixel resolution element. We clearly andunambiguously identify stochastic, structured patterns of intrinsicvariability at the 1%-2% level of the line flux in the broad C IIIλ5696 emission line. The λ5801/12 doublet emission is alsofound to be variable at the 0.2%-0.5% level of the line flux. We find acorrelation between the variability patterns observed in C III and C IV,which suggests a significant overlap in the emission volumes of thesetransitions, although C IV is known to arise somewhat closer to thestar. We attempt to reproduce the observed line profile variationpatterns using a simple phenomenological model, which assumes the windto be fully clumped. With a minimal set of assumptions, we are able toreproduce both the shape and the variability in the C III λ5696emission profile. We show that the variability pattern providesconstraints on the radial extent of WR 135's wind where C III isproduced, as well as on the local wind acceleration rate. However, oursimple clump model does not reproduce the lower variability in the C IVdoublet unless we assume the C IV emission to occur in a much largervolume than C III, implying that significant C IV emission occursfarther out in the wind than C III. We suggest that while some C IVemission might occur farther out, possibly because of reionization fromshocks, a more likely explanation is that wind clumping significantlyincreases with distance from the star, leading to larger variabilitylevels in C III, formed farther out than most of C IV. Alternatively,optical depth effects and/or local ionization gradients within clumpscould conspire to attenuate clumping effects in the C IV emission linewhile enhancing them in the C III line.
| Long-term photometry of the Wolf-Rayet stars WR 137, WR 140, WR 148, and WR 153
In 1991, a long term UBV-photometry campaign of four Wolf-Rayet starswas started using the 60 cm telescope of the National AstronomicalObservatory Rozhen, Bulgaria. Here we report on our observationalresults and discuss the light variations. The star WR 137 was observedduring 1991 - 1998. No indications of eclipses were found, though randomlight variations with small amplitudes exist, which are probably due todynamical wind instabilities. WR 140 was also monitored between 1991 and1998. In 1993, a dip in the light curve in all passbands was observedshortly after periastron passage, with amplitude of 0.03 mag in V. Thisis interpreted in terms of an ``eclipse'' by dust condensation in theWR-wind. The amplitude of the eclipse increases towards shorterwavelengths; thus, electron scattering alone is not sufficient toexplain the observations. An additional source of opacity is required,possibly Rayleigh scattering. After the eclipse, the light in allpassbands gradually increased to reach the ``pre-eclipse'' level in1998. The very broad shape of the light minimum suggests that a dustenvelope was built up around the WR-star at periastron passage bywind-wind interaction, and was gradually dispersed after 1993. Ourobservations of WR 148 (WR + c?) confirm the 4.3 d period; however, theyalso show additional significant scatter. Another interesting finding isa long-term variation of the mean light (and, possibly, of theamplitude) on a time scale of years. There is some indication of a 4year cycle of that long-term variation. We discuss the implications forthe binary model. Our photometry of WR 153 is consistent with thequadruple model of this star by showing that both orbital periods, 6.7 d(pair A) and 3.5 d (pair B), exist in the light variations. A search inthe HIPPARCOS photometric data also reveals both periods, which is anindependant confirmation. No other periods in the light variability ofthat star are found. The longer period light curve shows only oneminimum, which might be due to an atmospheric eclipse; the shorterperiod light curve shows two minima, indicating that both stars in pairB are eclipsing each other. Based on observations collected at theNational Astronomical Observatory Rozhen, Bulgaria
| Flux Distributions for 59 Stars in Cygnus
Absolute flux distributions are given for 59 Cygnus stars in thespectral range of 320--720 nm with a step of 5 nm. Their rms errors areon the average 2--4%. The synthetic color indices calculated for theflux distributions are compared with the observed color indices in threephotometric systems.
| Multiperiodicity in Pulsating Lambda Boo Star 29 Cyg (HD192640, V1644 Cyg)
Not Available
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
| 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.
| A survey for rapid variability among early main-sequence A stars
A survey of nonpeculiar early (A0-A5) main-sequence A stars for rapid,low-amplitude variability is presented. The survey is also anindependent test of the main-sequence mass-loss theory proposed byWillson et al. (1986). All observations were gathered with theUniversity of Wisconsin Two-Star Photometer. Several period-searchingmethods are used to analyze time series of differential-photometricdata. This instrument coupled with a computerized high-speed datacollection system was used with small telescopes at Pine BluffObservatory and Table Mountain Observatory. Several period-searchmethods are used to analyze time series of differential-photometricdata. This instrument and data-reduction technique allow millimagnitudelight variations to be detected. The survey also discovered severallow-amplitude Delta Sct stars, all of which are in or blueward of therecognized instability strip.
| An Atlas of Balmer Lines - H-Delta and H-Gamma
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..599C&db_key=AST
| A search for T Tauri's optical companion star
Speckle interferometric observations of the premain-sequence stellarsystem T Tauri at 650 and 800 nm, and at 1.6 (H) and 2.2 microns (K) inthe IR using the Palomar 200-in. telescope yield no evidence for atertiary optical companion star as reported in 1985. The presentobservations were of sufficient sensitivity to have detected the objectunambiguously if it had remained at its reported brightness and color.The IR results provide particularly stringent limits on the presence ofa third star in the system, since both the optical and southern IRcomponent are clearly resolved to the diffraction limit of the 200-in.telescope, including the H band where the southern component appearedabout 5 mag fainter than the optical primary. Possible resolutions tothe conflicting results concerning this object are discussed, and it isconcluded that if the star is bound to the T Tau system, it has dimmedby at least 1-3 mag at R, I, H, and K. The star is unlikely to be anormal M dwarf as reported, and the possibility that the star could be aHerbig-Haro object is discussed.
| Early-type stars in the stellar associations Per OB1, SCO OB1, and CYG OB1 by observations with space telescope 'Glazar'
This paper presents results of observations at 1640 A carried out inSeptember 1988 with the Soviet space telescope Glazar on the regions ofstellar associations Per OB1, Sco OB1, and Cyg OB1. Thirty twophotographs were obtained, on which 94 images of stars were identifiedand measured. In stellar associations Per OB1, Sco OB1, and Cyg OB1, 42,22, and 30 hot stars brighter than 10 mag at 1640 A were detected,respectively. A comparison of Glazar measurements of stellar magnitudeswith those available from TD-1 telescope measurements and from ANSmeasurements showed reasonably good agreement.
| The Distribution of Early Type Stars in the Direction of Stellar Associations PERSEUS-OB1 SCORPIUS-OB1 and CYGNUS-OB1
Not Available
| Spectrophotometry of stars in Cygnus
Preliminary results of the observations of 70 stars of early spectraltypes in Cygnus are presented. Spectrophotometric data have beenobtained which can be used to study the structure of the Galaxy withrelatively high reliability.
| Two-colour diagrams for differentially rotating stars
Not Available
| ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars
A survey of a sample of 672 stars from the Yale Bright Star Catalog(Hoffleit, 1982) has been carried out using speckle interferometry onthe 3.6-cm Canada-France-Hawaii Telescope in order to establish thebinary star frequency within the sample. This effort was motivated bythe need for a more observationally determined basis for predicting thefrequency of failure of the Hubble Space Telescope (HST) fine-guidancesensors to achieve guide-star lock due to duplicity. This survey of 426dwarfs and 246 evolved stars yielded measurements of 52 newly discoveredbinaries and 60 previously known binary systems. It is shown that thefrequency of close visual binaries in the separation range 0.04-0.25arcsec is 11 percent, or nearly 3.5 times that previously known.
| Some New Possible Variable Stars
Not Available
| The A0 stars
A photometric grid, standardized on MK spectral standards, has been usedto compare spectral types and luminosity classes obtainedphotometrically with those in two extensive spectral surveys coveringthe entire sky. Major discrepancies include the spectroscopicclassification of B9.5, which may indicate an otherwise unrecognizedspectral peculiarity, a different A0/A1 spectral type boundary in thetwo samples involved, the well-known misclassification of weak heliumstars, and an appreciable percentage of stars which are called dwarfsspectroscopically but are of higher photometric luminosity. The spacemotion vectors of these stars for which radial velocities are available,and excluding the minimum of 25 percent that are spectroscopic binarieswithout orbital elements, show structure in their distribution in the(U, V)-plane, with members of the Local Association and the Hyades andSirius superclusters forming obvious concentrations. The members of theLocal Association in the samples are mainly old (more than 200 millionyears) mode A stars, although a few much younger stars are included. Themembers of the Hyades and Sirius superclusters contain many bluestragglers, including several peculiar stars of the Hg, Mn, and Sivarieties.
| UVBY beta photometry and MK spectral classification.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24...69O&db_key=AST
| Rotational Velocities of a0 Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..101D&db_key=AST
| Catalogue d'etoiles O et B.
Not Available
| La mesure des vitesses radiales au prisme objectif. XV. 7e liste de vitesses radiales déterminées au prisme obtif à vision directe
Not Available
| Structure de la galaxie dans la région de P Cygni
Not Available
| Spectral Classification of 533 B8-A2 Stars and the Mean Absolute Magnitude of a0 V Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..159O&db_key=AST
| Stellar Spectra and Colors in an Irregular Region in Cygnus.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1953ApJ...118...77A&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hattyú |
| Rektaszcenzió: | 20h14m05.00s |
| Deklináció: | +36°36'19.0" |
| Vizuális fényesség: | 6.45 |
| Távolság: | 309.598 parszek |
| RA sajátmozgás: | 9.6 |
| Dec sajátmozgás: | -3.4 |
| B-T magnitude: | 6.449 |
| V-T magnitude: | 6.461 |
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