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Stellar Rotation in Young Clusters. II. Evolution of Stellar Rotation and Surface Helium Abundance
We derive the effective temperatures and gravities of 461 OB stars in 19young clusters by fitting the Hγ profile in their spectra. We usesynthetic model profiles for rotating stars to develop a method toestimate the polar gravity for these stars, which we argue is a usefulindicator of their evolutionary status. We combine these results withprojected rotational velocity measurements obtained in a previous paperon these same open clusters. We find that the more massive B starsexperience a spin-down as predicted by the theories for the evolution ofrotating stars. Furthermore, we find that the members of binary starsalso experience a marked spin-down with advanced evolutionary state dueto tidal interactions. We also derive non-LTE-corrected heliumabundances for most of the sample by fitting the He Iλλ4026, 4387, 4471 lines. A large number of heliumpeculiar stars are found among cooler stars withTeff<23,000 K. The analysis of the high-mass stars (8.5Msolar
| Stellar Rotation in Young Clusters. I. Evolution of Projected Rotational Velocity Distributions
Open clusters offer us the means to study stellar properties in sampleswith well-defined ages and initial chemical composition. Here we presenta survey of projected rotational velocities for a large sample of mainlyB-type stars in young clusters to study the time evolution of therotational properties of massive stars. The survey is based onmoderate-resolution spectra made with the WIYN 3.5 m and CTIO 4 mtelescopes and Hydra multi-object spectrographs, and the target starsare members of 19 young open clusters with an age range of approximately6-73 Myr. We made fits of the observed lines He I λλ4026,4387, 4471, and Mg II λ4481, using model theoretical profiles tofind projected rotational velocities for a total of 496 OB stars. Wefind that there are fewer slow rotators among the cluster B-type starsrelative to nearby B stars in the field. We present evidence consistentwith the idea that the more massive B stars (M>9 Msolar)spin down during their main-sequence phase. However, we also find thatthe rotational velocity distribution appears to show an increase in thenumbers of rapid rotators among clusters with ages of 10 Myr and higher.These rapid rotators appear to be distributed between the zero age andterminal age main-sequence locations in the Hertzsprung-Russell diagram,and thus only a minority of them can be explained as the result of aspin-up at the terminal age main sequence due to core contraction. Wesuggest instead that some of these rapid rotators may have been spun upthrough mass transfer in close binary systems.
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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 beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| 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.
| Precise positions of reference stars in open clusters NGC 457 and NGC 581.
Not Available
| Stellar Content of Young Open Clusters - Part Two - Be-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982A&A...109...48M&db_key=AST
| Drei-Farben-Photometrie von 11 offenen Sternhaufen, insbesondere solchen mit O-und frühen B-Sternen. Mit 21 Text-abbildungen
Not Available
| A photographic survey of galactic clusters. V. NGC 189, I 1590, NGC 358, 366, 381, 433, 436, 457, 609, 637, I 166, NGC 743
Not Available
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