Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
|
Young Stars far from the Galactic Plane: Runaways from Clusters
Quite recently, a significant number of OB stars far from the galacticplane have been found, situated at z-distances ranging from severalhundreds of pc to several kpc. The short lifetimes of these stars poseproblems for their interpretation in terms of the standard picture ofstar formation. Different mechanisms have been put forward to explainthe existence of these stars, either within the conventional view, orpostulating star formation in the galactic halo itself. These mechanismsrange from arguing that they are misidentified evolved or abnormalstars, to postulating powerful ejection mechanisms for young disk stars;in situ formation also admits several variants. We have collected fromthe literature a list of young stars far from the plane, for which theevidence of youth seems convincing. We discuss two possible formationmechanisms for these stars: ejection from the plane as the result ofdynamical evolution of small clusters (Poveda et al. 1967) and in situformation, via induced shocks created by spiral density waves (Martos etal. 1999). We compute galactic orbits for these stars, and identify thestars that could be explained by one or the other mechanism. We findthat about 90 percent of the stars can be accounted for by the clusterejection mechanism, that is, they can be regarded as runaway stars inthe galactic halo.
|
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 high-resolution optical and radio study of Milky Way halo gas
Optical interstellar absorption lines of Ti II and Ca II and the 21 cmemission line of H I were observed at high-resolution (6 and 1 km/s,respectively) and high detection sensitivity along 25 lines of sight inthe Galactic halo. The sample includes 16 distant halo stars matchedwith one or more nearly aligned foreground stars as well as local starsalong five extragalactic sight lines. The data show substantialinterstellar material, at both low and intermediate velocities, between250 and 1000 pc beyond the Galactic plane. As much as one-third of thetotal gas observed in Ca II absorption may be beyond 1 kpc, and thegaseous Ti II may lie in an even thicker layer. The directly determinedgaseous Ti abundance above the Galactic plane exceeds that in the disk,on the average, by a factor of 4 to 6 and, for individual cloudcomponents, is further enhanced at higher LSR velocity. Thirty threediscrete high-latitude clouds are detected in Ca II absorption, and 17discrete clouds, including three high-velocity clouds, are identified inH I emission. The kinematics of the high-latitude gas observed in Ti IIand Ca II absorption is characterized by significant peculiar velocitieswith respect to a model corotating halo.
|
Iron and molecular opacities and the evolution of Population I stars
Effects of recent opacity revisions on the evolution of Population Istars are explored over the range 1.5-60 solar masses. Opacityparameters considered include the angular momentum coupling scheme foriron, the relative iron abundance, the total metal abundance, anddiatomic and triatomic molecular sources. Only the total metal abundanceexerts an important control over the evolutionary tracks. Blue loops onthe H-R diagram during core helium burning can be very sensitive toopacity, but only insofar as the simple formation or suppression of ablue loop is concerned. The blue loops are most robust for stellarmasses around 10 solar masses. We confirm, from a comparison of stellarmodels with observational data, that the total metal abundance is closeto solar and that convective core overshooting is likely to be veryslight. The new models predict the existence of an iron convection zonein the envelope and a great widening of the main-sequence band in theH-R diagram at luminosities brighter than 100,000 solar luminosities.
|
The runaway nature of distant early-type stars in the galactic halo
The kinematics of a sample of 32 distant halo B-stars with masses in therange 3-21 solar masses are investigated using the current 'runawaystar' hypotheses to establish if they belong to this group of stars.Whether postmass transfer secondaries in evolved massive close binariescan be normal low mass B-stars is discussed, but support for this ideais not found. Thus it appears that the lower mass stars could not havebeen ejected out of the disk as a result of supernova explosions inmassive close binaries, while the higher mass objects do not in generalreveal a binary nature as expected from this theory. The results ofrecent N-body simulations of the purely dynamical ejection of runawaystars from young galactic star clusters are in excellent agreement withthe observations. Thus it appears that these halo stars are the mostdistant subgroup of OB runaways produced by cluster ejection yetobserved.
|
Catalog of mean stellar radial velocities (catalog on magnetic tape)
A catalog of the mean radial velocities for 6451 Galactic stars isdescribed, which supplements the General Catalogs of Wilson (1953) andEvans (1978) with published observations up to December, 1980. Onlyobservations with adequate spectral resolution and standardized to theIAU or Wilson velocity systems are included in the catalog. The accuracyand sources of the data, and the weighting system used in constructingthe catalog are discussed. A sample section of the catalog is presentedand explained.
|
Interstellar CA II absorption toward early-type stars at high Galactic latitudes
New high resolution AAT and INT observations of the Ca II 3933 Åinterstellar line towards nine early-type stars at high galacticlatitudes are presented. These are combined with the authors' earlierAAT data to investigate the distribution of Ca II in the galactic halo.A comparison of these results with Ca II equivalent widths forextragalactic sightlines implies that there is a significant amount ofthis ion out to z ≅ 1 kpc, but not much beyond z ≅ 2 kpc. Nocoincident high velocity Ca II absorption is detected in the spectra ofstars near known high velocity clouds (HVC). Although this may indicatethat the HVCs are either at greater distances than the stars or haveangular extents smaller than the separations of the stellar and HVCsightlines, it is also possible that they are nearby but contain toolittle Ca II to produce an observable absorption line.
|
A search for far-infrared (IRAS) emission from early-type stars at high Galactic latitudes
Recently Lamers et al. (1986) have found that HR 4049 (B supergiant at z= 1300 pc) is surrounded by a dust cloud which produces a large IRexcess, from which it is inferred that the star may be a much lessluminous low mass object close to the Galactic plane. Here, the resultsof a search for strong FIR (IRAS) emission from a sample of early-typehigh-Galactic-latitude stars, estimated to be at z-distances of up to9000 pc from optical spectral analyses, are reported. No IR emission wasdetected for any of the stars investigated, which would not be expectedif they were nearby objects with dust clouds. It is therefore concludedthat they are normal stars at the large distances previously estimated.
|
Observations of early-type stars at high galactic latitudes
Using equivalent widths and line profiles measured from high resolutionAAT spectra in conjunction with model atmosphere calculations, it isshown that a sample of eleven high galactic latitude early-type starsare normal, distant objects. Stellar velocities in the z-directiondetermined from the spectra, coupled with the galactic gravitationalfield g(z), allow the times the stars would have taken to reach theirpresent positions if they were ejected from the disc to be derived. Acomparison of these times with the evolutionary ages indicate that atleast four of the stars have been formed in situ, possibly from galacticfountain material.
|
Four-colour and H beta photometry of southern B stars at high galactic latitudes
Four-color and H beta photometry has been obtained for 105 early-type HDstars with galactic latitudes less than -45 deg. They are mostly late Bstars of luminosity class V to III. Two new Am stars and several Ap orBp stars are detected photometrically. Absolute magnitudes aredetermined from the photometry and from MK types where available. Theinterstellar reddening of many of the more distant stars is very small,suggesting either the existence of undetected peculiar stars in thesample or that there are areas of effectively zero reddening at highsouthern galactic latitudes.
|
Spectroscopically peculiar stars near the south galactic pole.
Abstract image available at:http://adsabs.harvard.edu/abs/1973AJ.....78..295G
|
Radial Velocities and Spectral Classification of A-Type Stars Near the South Galactic Pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..643B&db_key=AST
|
A finding list of early-type stars near the south galactic pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..338S&db_key=AST
|
Stellar-Population Samples at the Galactic Poles. II. UBVRI Photometry of M Stars Near the South Pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...22..289E&db_key=AST
|
Line strengths for southern OB stars-II. Observations with moderate dispersion
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969MNRAS.144...31B&db_key=AST
|
Three-colour photometry of early-type stars near the galactic poles
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.127...83W&db_key=AST
|
Radial velocities of bright southern stars, III
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.126...29B&db_key=AST
|
