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Abundance analysis of late B stars. Evidence for diffusion and against weak stellar winds
Based on high S/N spectra obtained at La Silla, Chile, and the SpecialAstrophysical Observatory, Russia, the abundances of He, C, O, Ne, Mg,Si, Ca, Fe, Sr, and Ba in 27 optically bright B5-B9 main-sequence starswere determined. NLTE effects were taken into account. A variety ofabundance patterns is present in late B stars. Accurate surfaceabundances of the diffusion indicators O, Mg, Ca, Sr and Ba suggest thatelement stratification due to diffusion is common in the program stars.Models of stellar atmospheres which include meridional mixing canexplain the observed anomalies. Although the program stars representonly a volume-limited sample of the solar neighbourhood this result isimportant for the cosmochemical evolution of the Galaxy: the surfaceabundances of the stars investigated do not necessarily reflect thechemical composition of the interstellar cloud they originated from.Furthermore, five program stars show narrow absorption lines in Ca II Kwhich can be attributed to circumstellar gas. Neon serves as a traceelement for the occurrence of weak stellar winds. Neon overabundances ofsome stars derived under the assumption of LTE suggest that such windshave been detected. In sharp contrast, the more realistic treatment ofNLTE leads to solar neon abundances and thus reveals that weak stellarwinds are absent in the program stars.Based on observations collected at the European Southern Observatory, LaSilla, Chile and at the Special Astrophysical Observatory, NizhnijArkhyz, Russia.
| 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
| 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
| Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
| Four-colour photometry of eclipsing binaries. XXXVIII. Light curves of the triple system V906 Scorpii
Complete $uvby$ light curves of the detached triple-lined late B-typeeclipsing binary V906 Scorpii, secured from 1987 to 1991, are presented.A detailed photometric analysis based on these observations and on newspectroscopic material yields accurate masses and radii (errors <~2%) for the components, confirms that the system is a member of NGC 6475(Messier 7), and is published separately \cite[(Alencar et al.1997)]{ale97}. Based on observations done with the Danish 50 cmTelescope (SAT) at the European Southern Observatory (ESO), La Silla,Chile. Table 2 presented in this paper will only be accessible inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Absolute dimensions of eclipsing binaries. XXI. V906 Scorpii: a triple system member of M 7.
We present an analysis based on new uvby light curves and spectroscopicdata of the detached triple-lined B-type eclipsing binary V906 Sco. Theuvby light curves are analysed with an extended version of theWilson-Devinney program. The spectroscopic CCD observations are analysedwith both the Sterne and the Lehmann-Filhes methods. We conclude fromthe combined analysis that the triple system V906 Sco is a member of theopen cluster M 7 and that its B-type eclipsing components are still onthe main sequence, at an age of (2.4+/-0.3)x10^8^yrs, already close tothe TAMS (especially the more massive one). The system is older than thetime for circularization of the orbit, and the small eccentricity isprobably caused by the third component, which, however, is unlikely tobe the main responsible for the apsidal motion, probably more influencedby tidal and rotational deformation. We determine absolute dimensions ofhigh precision (errors <2%): M_A_=3.25+/-0.07, R_A_=3.52+/-0.04,M_B_=3.38+/-0.07 and R_B_=4.52+/-0.04, in solar units. The system isdetached, with both components in synchronous rotation, and thereforerepresentative for normal stars.
| 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.
| An X-Ray Survey of the Open Cluster NGC 6475 (M7) With ROSAT
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1229P&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.
| Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
| The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
| Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| Chemically peculiar stars in open clusters. I - The catalog
The largest existing compilation is presented of Ap and Am open clusterstars. The catalog contains information on 381 chemically peculiar (CP)stars of the upper main sequence in 79 open clusters. The catalog iscomposed of the following tables: (1) the main body, which lists CP (orsuspected CP) stars which are kinematical (or suspected kinematical)members of open clusters; (2) the list of CP (or suspected CP) starssometimes numbered among cluster members but which are actuallykinematical nonmembers; (3) the list of stars sometimes designated as'peculiar' but, in fact, probably not CP; (4) references for numberingsystems of cluster stars; (5) references for membership; and (6)references for spectral and/or peculiarity types.
| Catalog of AP and AM stars in open clusters
The previous results of Raab (1922), Markarian (1951), and Collinder(1931) have been used to catalog Ap and Am stars that are in the fieldof open clusters. Tabular data are presented for the clusterdesignation, the HD or HDE number, the right ascension (1900), thedeclination (1900), and the magnitude. Also listed are the spectraltypes and, for certain stars, the probability of cluster membership.
| The early A type stars - Refined MK classification, confrontation with Stroemgren photometry, and the effects of rotation
The MK classification system for the early A-type stars is refined, anda parallel system of standards for the broad-lined stars is introduced.With this improved system, stars may be classified with significantlygreater precision than before. It is shown that spectral types in thissystem are not systematically affected by rotational line broadening. Atotal of 372 early A-type stars are classified, and a confrontation ofthese spectral types with Stroemgren photometry reveals a number ofsystematic photometric effects of rotation. In particular, high v sin istars are systematically redder than low v sin i stars of the samespectral type, and the beta index is weakened by rotation. It isconcluded that precise spectral classification in conjunction withStroemgren and H-beta photometry can potentially provide a valuablecheck and input to the theory of the atmospheres of rotating stars.
| Radial velocities and membership probabilities in the open star cluster NGC 6475 (M 7)
For 76 stars in the field of the open cluster NGC 6475, calibratedobjective prism radial velocities with a mean observational error near +or - 2 km/s are presented. HD 163302 has been detected to be a newspectroscopic binary. Preliminary orbital elements are given. Clusterand field stars are separated kinematically by their widely differentvelocity dispersions. A statistical interpretation of the velocitydistribution reveals quantitative membership probabilities. A largefraction of cluster members are still identified beyond the conventionalcluster radius. HD 162067 is discovered to be a high-velocity star witha radial velocity of nearly 100 km/s of approach.
| 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.
| Radial velocities of bright southern stars. I - 139 B-type HR and FK stars
Radial velocity determinations for 139 southern B stars in the BrightStar, FK4, and FK4 Supplement catalogues and for 53 bright southernlate-type stars are presented, based on coudespectrograms taken with theESO 1.5 m telescope at La Silla. The programs, observations,measurements, and reductions are described. Among the data presented arethe visual magnitude, spectral class, mean error, E/T variabilityparameter, velocity of interstellar lines, and rotation class.
| The open cluster NGC 3532
NGC 3532 is a large cluster in the Carina region of the southern MilkyWay. Observations in the modified Stromgren and H beta systems have beenobtained for 33 stars. (R,I) photometry for the red stars is listed in atable. The HD and CPD numbers for the 33 stars are also listed togetherwith the numbers assigned by Koelbloed. Attention is given to reddeningand luminosity determinations, the red giants in the cluster region, acomparison of computed and cluster luminosities for some of thecalibrating stars, and age considerations. It is pointed out that theusefulness of NGC 2287 and 3532 for testing stellar models is increasedby the existence of a third, bright cluster of intermediate age, NGC6475.
| Relative radial velocities from objective prism spectra in the region of nine southern open star clusters and a star field at Eta Carinae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..245G&db_key=AST
| Properties of AM stars in the Geneva photometric system
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....92..289H&db_key=AST
| The occurrence of abnormal stars in open clusters
The age dependence of the frequencies of various types of abnormal starsin open clusters and associations is discussed. Spectra acquired atdispersions of 39 A/mm and 129 A/mm were used to determine the spectraltypes and luminosity classes of 661 stars in 14 open clusters andassociations. The frequencies of Ap(Si), Ap(Hg,Mn) and Ap(Sr,Cr) starsare found to increase with age to a level about that of field stars,while the rotational velocities of Ap(Si) and Ap(Hg,Mn) stars decreasewith time. Be stars in clusters exhibit a relatively constant frequency,roughly equal to that of Be field stars. The frequencies of stars withpronounced shell spectra are observed to remain constant with age, whilestars with unusually broad hydrogen lines (Vb stars) occur only in theyoungest clusters. The frequency of Am stars in clusters is notsignificantly different from that of field stars, and does not seem todepend on age, although rotational velocity is seen to decrease. It isconcluded that Ap or Am stars develop from stars of various rotationalspeeds, with a subsequent decrease in rotational velocity.
| Errata in the "Bibliography of Stellar Radial Velocities" by H. A. Abt & E. S. Biggs
Not Available
| The spectroscopic binaries in NGC 6475
Using objective-prism spectra obtained with a radial-velocityastrograph, a large number of radial velocities of 13 of the brightestmembers in NGC 6475 have been determined. Three of five previouslysuspected short-period spectroscopic binaries could not be confirmed.However, two of these three stars seem to be long-period spectroscopicbinaries. The remaining two suspected binaries could be confirmed, andelements have been derived. It is concluded that the frequency ofshort-period spectroscopic binaries in NGC 6475 is considerably smallerthan supposed earlier. Finally, general properties of the techniqueemployed for the determination of relative radial velocities arediscussed.
| Nomenclature cross-correlation for stars in NGC 2516 and NGC 6475
Not Available
| Catalog of spectrophotometric scans of stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...32....7B&db_key=AST
| Evolved stars in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...30..451H&db_key=AST
| Spectral types in the open cluster NGC 6475.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..417A&db_key=AST
| The Evolutionary Status of the Blue Halo Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJS...26...37N&db_key=AST
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Scorpione |
| Ascensione retta: | 17h54m27.20s |
| Declinazione: | -34°27'59.0" |
| Magnitudine apparente: | 5.96 |
| Distanza: | 258.398 parsec |
| Moto proprio RA: | 3.2 |
| Moto proprio Dec: | -4.5 |
| B-T magnitude: | 6.15 |
| V-T magnitude: | 6.098 |
Cataloghi e designazioni:
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INHABITED SKY
