Spectroscopic study of the open cluster Blanco 1
Aims: As a part of our program on binaries in open clusters, we presenta spectroscopic study of the bright stars of Blanco 1 aimed at detectingand characterizing spectroscopic binaries. Methods: Forty fivestars previously mentioned as cluster candidates, plus another 24 starsin a wider region around the cluster were observed repeatedly during 6years, with a spectral resolving power 13 300. Radial velocities weremeasured by cross-correlations. Results: We obtained a meancluster velocity of 6.2 ± 0.3 km s-1 and determinedkinematic membership. Eleven spectroscopic binaries were detected, andorbital solutions are presented for eight of them. Six binaries areconfirmed to be members of the cluster. All of them are single-linedspectroscopic systems with periods in the range 1.9-1380 days.Considering all suspected binaries, the cluster binary frequency amountsto about 50%.Based on observations obtained at the Complejo Astronómico ElLeoncito (CASLEO), Argentina.
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Triggered Star Formation by Massive Stars
We present our diagnosis of the role that massive stars play in theformation of low- and intermediate-mass stars in OB associations (theλ Ori region, Ori OB1, and Lac OB1 associations). We find thatthe classical T Tauri stars and Herbig Ae/Be stars tend to line upbetween luminous O stars and bright-rimmed or comet-shaped clouds; thecloser to a cloud the progressively younger they are. Our positional andchronological study lends support to the validity of theradiation-driven implosion mechanism, where the Lyman continuum photonsfrom a luminous O star create expanding ionization fronts to evaporateand compress nearby clouds into bright-rimmed or comet-shaped clouds.Implosive pressure then causes dense clumps to collapse, prompting theformation of low-mass stars on the cloud surface (i.e., the bright rim)and intermediate-mass stars somewhat deeper in the cloud. These starsare a signpost of current star formation; no young stars are seenleading the ionization fronts further into the cloud. Young stars inbright-rimmed or comet-shaped clouds are likely to have been formed bytriggering, which would result in an age spread of several megayearsbetween the member stars or star groups formed in the sequence.
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3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
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Speckle Interferometry of Southern Double Stars. II. Measures from the CASLEO 2.15 Meter Telescope, 1995-1996
Relative astrometry is presented for 198 observations of 160 doublestars. The data were obtained at the 2.15 m telescope at the ComplejoAstronómico El Leoncito (Argentina) with a multianodemicrochannel array (MAMA) detector system. Five high-qualitynondetections are also reported. When judged against ephemeris positionsfor binaries with very well determined orbits, the separation residualsexhibit a root mean square deviation of13.2+3.4-1.9 mas and the position angle residualsexhibit rms deviation of 2.9d+0.8d-0.5d. Factorsaffecting the measurement precision are discussed.
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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
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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
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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
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Spectroscopy of the open cluster Blanco 1 II. H alpha emission as an indicator of relative age
We present the results of H alpha (6562\AA) and Li i (6708\AA)observations of 114 low-mass stars of the young open cluster Blanco 1.We also present observations of 30 stars in Ca ii(K). This work extendsthe first Blanco 1 spectroscopic study of Panagi et al. (1994). From asample of four well-studied clusters, including Blanco 1, we find thatthe fraction of H alpha emission-line stars amongst K dwarfs is a goodindicator of relative age, with a smaller fraction indicative of olderage. Blanco 1 shows a relatively small fraction of emitters,inconsistent with previous age estimates for the cluster. We estimatethe cluster age to to be 90 +/- 25 Myr, slightly older than thePleiades. The method is shown to be more sensitive to age than lithiumand a useful alternative to other age measurement techniques. Thevariation of H alpha with (B-V) is similar to that observed in the oldersolar neighbourhood dwarfs, suggesting that, at least for theabsorption-line stars, the contribution of stellar rotation to theequivalent width is unclear. We combine both spectroscopy and photometryto revise cluster membership and give accurate positions for all thesestars. Tables A1 and A2 are available at the CDS via anonymous ftp130.79.128.5 or http://cdsweb.u-strabg.fr./Abstract.html
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Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
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Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
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Bibliographic Catalogue of Stellar Radial Velocities
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&AS...85..885B&db_key=AST
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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.
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UBV and uvby-beta photometry of stars in the region of the Zeta SCULPTORIS cluster
Photoelectric observations of 130 stars in the region of Zeta Sculptorishave been obtained in UBV and uvby-beta. A total of 32 stars areidentified as cluster members, and several other F and G type stars areidentified as probable members. Results indicate an interstellarreddening of E(B-V) = 0.02 mag and that the cluster is slightly metaldeficient.
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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.
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Bibliographic Catalogue of Stellar Radical Velocities
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...65...59B&db_key=AST
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The common origin of some open clusters
Eight open clusters have been observed with uvby-beta photometry and forseven of them the metal abundances have been determined. Six of thesehave similar metallicities. They are close in space and are also knownto have similar ages and radial velocities. These clusters are suspectedof having a common origin. Some studies are made of the reliability ofthe photometric system. A large gain in limiting magnitude can beachieved against an unimportant loss of accuracy if interference filtersare removed.
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Open clusters and galactic structure
A total of 610 references to 434 clusters are employed in thecompilation of a catalog of open clusters with color-magnitude diagramson the UBV or RGU systems. Estimates of reddening, distance modulus, ageand number of cluster members are included. Although the sample isconsidered representative of the discoverable clusters in the galaxy,the observed distribution is nonuniform because of interstellarobscuration. Cluster distribution in the galactic plane is found to bedominated by the locations of dust clouds rather than by spiralstructure. The distributions of clusters as a function of age andrichness class show that the lifetimes of poor clusters are much shorterthan rich ones, and that clusters in the outer disk survive longer thanthose in the inner disk. An outer disk age which is only about 50% theage of the globular clusters is indicated by cluster statistics. Thethickening of the galactic disk with increasing galactocentric distancemay be due to either a younger dynamical age or a lower gravitationalpotential in the outer regions.
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Spectral types in the Zeta SCULPTORIS open cluster
The spectral types of 20 stars in the Blanco 1 open cluster (ZetaSculptoris) are reported. Spectral classification in the MK system wasperformed on the basis of 125-A/mm dispersion spectra obtained with a0.9-m telescope and a Cassegrain spectrograph. Of the stars classified,one classical Am star, one peculiar star with a weak K-line and one Apstar with marginal Si II lines enhancement were found, while the starZeta Scl itself is observed to be a main sequence object and thusprobably a foreground star. An H-R diagram of the cluster is alsopresented, and other probable members and nonmembers are indicated.
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Multicolor photometry of the ZET Scl open cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90...81P&db_key=AST
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Evolved stars in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...30..451H&db_key=AST
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Optical polarization of stars of galactic latitudes b-45 degres.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...23..125S&db_key=AST
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A finding list of stars of spectral type A7 and earlier in regions at high galactic latitudes. VI. Near South Galactic Pole.
Not Available
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NGC 2516 and the Pleiades Group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...173...63E&db_key=AST
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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
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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
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A Very Young Cluster with a Moderate Metal Deficiency
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJ...161..159E&db_key=AST
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Stellar kinematics and evolution
Not Available
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Four-color photoelectric photometry of two high-latitude clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..556E&db_key=AST
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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
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INHABITED SKY
