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Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| 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
| The Normal Energy Distributions in Stellar Spectra: Giants and Supergiants
We have derived the normal spectral energy distributions for thoseearly-type subgiants, giants, and supergiants that were not investigatedin our earlier studies, which were in most cases also not included inthe studies of Sviderskiene. Color indices computed using our normalenergy distributions are in good agreement with normal colors derivedfrom observations in the Vilnius photometric system. The reliability ofour distribution curves is also demonstrated by comparisons of observedand computed (W-B)-(B-V) two-color diagrams in the WBVR system. Normalcolor indices for the photometric WBVR system are derived.
| 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
| Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
| UBV photometry of P Cygni in 1995-1997
Based on UBV photometry taken over the years of 1995 to 1997 we foundthat P Cygni was in average fainter and hotter than it had been at thebeginning of the current decade. This fact allowed us to suggest thatthe star was probably at or near the minimum phase of a normal SD cycle,typical for other LBVs. Superimposed on this SD cycle we observed arapid decrease in brightness - by about 0145 for 30 days -- with colourbehaviour, at least in U-B, "bright and bluer". We suggested this was adescending branch of an " Cyg-type variation". Such variations seems tobe typical near the minima of the SD phases in other LBVs (Van Genderenet al., 1998; Sterken et al., 1998.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| 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.
| The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
| 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.
| Anomalous Proper-Motions in the Cygnus Super Bubble Region
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101...37C&db_key=AST
| Some revisions to the Bright Star Catalogue and its supplement
Not Available
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| New bright hydrogen emission stars III
Three-hundred-sixteen bright early-type stars not known to exhibithydrogen emission have been observed at H-alpha. Ten new emission starshave been found. One of the stars, HD 147196, is a probable member ofthe upper Scorpius association.
| 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
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| 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.
| 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.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Be stars in binaries
The known companions to 80 Be stars and 355 B stars listed in the BrightStar Catalogue in the range B1-B7 III-V and north of delta = -30 deg areconsidered. The known near-absence of Be binaries with periods less than1/10 yr is confirmed. For longer periods up to the limit of 10,000 AU ofthis survey, the Be and B stars do not differ in binary frequencies.This result implies that during pre-main-sequence contraction, the tidalbraking in binaries wider than 0.5 AU was inadequate to prevent theformation of stars with nearly the break-up rotational velocities. Thefraction of Be and B stars that have companions is higher in clustersand associations (38 percent) than among field stars (25 percent),confirming that escapees from clusters tend to be single stars. There issome evidence that the companions of Be stars that occur in the sameluminosity range tend also to be Be stars; that result was expectedbecause in visual binaries there is a known tendency for rapidlyrotating primaries to have rapidly rotating secondaries.
| Distribution of OB stars and absorbing matter in the region around P CYG
The results of spectrophotometric observations of 277 OB stars in a 7 x7-deg region around P Cyg, obtained in 8-sec, 45-sec, and 8-minexposures on ORWO ZU-21 plates with a 4-deg 272-A/mm-dispersionobjective prism on the 40-in. Schmidt telescope at BiurakanAstrophysical Observatory on October 14-19, 1979, are presented intables and graphs and characterized. Data reported include 400-480-nmabsolute spectrophotometric gradients, color excesses, and distances. Itis found that concentrations of OB stars with associated absorbingmatter exist toward the associations Cyg OB9 (two concentrations at 800and 1800 pc), Cyg OB3 (three concentrations at 1.4, 2.5, and 3.7 kpc),OB1 (at 1.6 kpc), Cyg OB8 (at 1.5 kpc), and over the entire observedregion at a distance of about 500 pc.
| Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
| Late B-type stars - Rotation and the incidence of HgMn stars
High-dispersion spectrograms for an unbiased sample of 256 late B-typestars are examined in an attempt to determine whether slow rotation isnecessary and sufficient for the appearance of HgMn anomalies innonmagnetic stars. The peculiar stars in the sample are identified,values of v sin i are derived for all the stars observed, and theradial-velocity variations of the identified HgMn stars are analyzed.The distribution of rotational velocities for late B-type stars isobtained, and the role of rotation in producing extended envelopes isevaluated. The binary frequency and mass-ratio distribution are derivedfor systems containing HgMn components, the effect of duplicity on thedistribution of rotational velocities is estimated, and the role of suchfactors as rotation, age, and binary characteristics in determiningwhether HgMn anomalies are present is investigated. The results clearlyshow that HgMn stars occur only within a limited temperature range, thatall such stars rotate slowly, but that rotation, effective temperature,age, surface gravity, and binary properties do not serve to determinewhether a star will exhibit abundance anomalies.
| The spectral classification of some stars in the GAM CYG neighbourhood.
Not Available
| Structure and age of the local association /Pleiades group/
Intermediate-band indices are used to derive luminosities for some 500early-type stars with well-determined proper motions and radialvelocities. Space motion vectors and galactic coordinates are computedfor the stars considered. It is found that the local association membersare mainly concentrated in the Sco-Cen region in the Southern Hemisphereand the Cas-Tau region in the north.
| Catalogue of early-type stars measured in a narrow-band photometric system
A compilation of the photoelectric measurements in the Barbier-Morguleffsystem is presented. The catalogue includes data for 773 stars ofspectral type 08 to F6. 706 stars have been measured at least twice.
| The Kinematics of the Gould Belt: an Expanding Group?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJS...17..371L&db_key=AST
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Observation and Astrometry data
| Constellation: | Schwan |
| Right ascension: | 20h16m28.20s |
| Declination: | +37°03'23.0" |
| Apparent magnitude: | 6.48 |
| Distance: | 349.65 parsecs |
| Proper motion RA: | -0.6 |
| Proper motion Dec: | 1.6 |
| B-T magnitude: | 6.335 |
| V-T magnitude: | 6.433 |
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