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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.
| Membership, binarity, and rotation of F-G-K stars in the open cluster Blanco 1
Context: The nearby open cluster Blanco 1 is of considerableastrophysical interest for formation and evolution studies of openclusters because it is the third highest Galactic latitude clusterknown. It has been observed often, but so far no definitive andcomprehensive membership determination is readily available. Aims: An observing programme was carried out to study the stellarpopulation of Blanco 1, and especially the membership and binaryfrequency of the F5-K0 dwarfs. Methods: We obtainedradial-velocities with the CORAVEL spectrograph in the field of Blanco 1for a sample of 148 F-G-K candidate stars in the magnitude range 10
| Bright Metal-poor Stars from the Hamburg/ESO Survey. I. Selection and Follow-up Observations from 329 Fields
We present a sample of 1777 bright (91.0) metal-poor([Fe/H]<-2.0) giants of 9%+/-2%, which is lower than previouslyreported. However, the frequency rises to similar (>20%) and highervalues with increasing distance from the Galactic plane. Although thenumbers of stars at low metallicity are falling rapidly at the lowestmetallicities, there is evidence that the fraction of carbon-enhancedmetal-poor stars is increasing rapidly as a function of decliningmetallicity. For ~60 objects, high-resolution data have already beenobtained; one of these, HE 1327-2326, is the new record holder for themost iron-deficient star known.
| Elemental abundances in the Blanco 1 open cluster
High-resolution spectroscopy is used to determine the detailed chemicalabundances of a group of eight F- and G-type stars in the young opencluster Blanco 1. An average [Fe/H] of +0.04 +/- 0.02 (internal error)+/- 0.04 (external error) is found, considerably lower than a previousspectroscopic estimate for this cluster. The difference is due mainly toour adoption of significantly cooler temperatures that are consistentwith both photometric and spectroscopic constraints. Blanco 1 exhibitssubsolar [Ni/Fe](-0.18 +/- 0.01 +/- 0.01), [Si/Fe](-0.09 +/- 0.02 +/-0.03), [Mg/Fe](-0.14 +/- 0.02 +/- 0.03) and [Ca/Fe](-0.09 +/- 0.03 +/-0.03); ratios that are not observed among nearby field stars. Thematerial from which Blanco 1 formed may not have been well mixed withinterstellar matter in the galactic disc, which tallies with its currentlocation about 240pc below the galactic plane. A simultaneous deficit ofNi and alpha elements with respect to Fe is hard to reconcile with mostpublished models of yields from supernovae of types Ia and II. Therevised abundances for Blanco 1 indicate that overall radiativeopacities in its stars, and hence convective zone properties at a givenmass, are similar to those in the Pleiades at approximately the sameage. This can explain a previous observation that the Li-depletionpatterns of G- and K-type stars in the two clusters areindistinguishable. The lower overall metallicity of Blanco 1 now makesit less attractive as a target for discovering transiting, short-periodexoplanets.
| Catalogue of [Fe/H] determinations for FGK stars: 2001 edition
The catalogue presented here is a compilation of published atmosphericparameters (Teff, log g, [Fe/H]) obtained from highresolution, high signal-to-noise spectroscopic observations. This newedition has changed compared to the five previous versions. It is nowrestricted to intermediate and low mass stars (F, G and K stars). Itcontains 6354 determinations of (Teff, log g, [Fe/H]) for3356 stars, including 909 stars in 79 stellar systems. The literature iscomplete between January 1980 and December 2000 and includes 378references. The catalogue is made up of two tables, one for field starsand one for stars in galactic associations, open and globular clustersand external galaxies. The catalogue is distributed through the CDSdatabase. Access to the catalogue with cross-identification to othersets of data is also possible with VizieR (Ochsenbein et al.\cite{och00}). The catalogue (Tables 1 and 2) is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/373/159 and VizieRhttp://vizier.u-strasbg.fr/.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Abundance analysis and origin of the ζ SCULPTORIS open cluster.
We have determined chemical abundances and radial velocities for starsin the field of the ζ Sculptoris cluster. We find that the clustermetal deficiency previously found from UBV photometry is not supported;the cluster overall metallicity, [Fe/H]=+0.23, is about 70% higher thanthe solar value. The chemical abundance pattern appears unusual: theNi/Fe ratio is lower than typical for field stars with similar Fe and Caabundances, and the cluster may also be deficient in the α elementSi. For its age, the cluster is unusually far from the galactic disk,=~240pc. The adopted heliocentric cluster radial velocity, +3.9km/s,shows that it is close to its maximum distance from the galactic plane.We suggest that the ζSculptoris cluster was formed in the galacticdisk 45Myr ago by the interaction of a high velocity cloud with theinterstellar medium, and that its formation may be connected with thatof Gould's Belt.
| 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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