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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
| 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
| 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.
| Spectroscopy of the young cluster Blanco 1
We present spectroscopic observations of some 115 stars of the clusterBlanco 1, extending from the Ca II(H,K) region to the Ca II(I-R)triplet, supporting an age similar to that of the young cluster alphaPersei. The H-alpha absorption equivalent with vs (B - V) diagram formsa well-defined locus, with decreasing absorption equivalent width fordecreasing effective temperature, akin to solar neighborhood dwarfs. Alarge spread in the Ca II surface flux, as a function of (B - V), alsoindicates the presence of a high degree of surface inhomogeneity,synonymous with high magnetic activity in young stars. A drop-off in theCa II flux at (B - V) = 1.0 is also similar to the solar neighborhoodstars, and shows that the primary chromospheric cooling changes from theCa II and Mg II lines to the Balmer lines. The mean chromospherictemperature for stars at 4800 K lies between 8000 K and 10,000 K, basedon theoretical models, which is somewhat higher than the older solarneighborhood dwarfs. The high mean Ca II surface flux of the sample isalso consistent with that of other young clusters. We were able tomeasure the equivalent width of the Li(6708) line, whose strength as afunction of (B - V) indicates an age similar to the young cluster alphaPersei. The lithium abundance decreases with decreasing effectivetemperature, consistent with the premise of lithium depletion in starswith larger convection zones. Using published photometry and a recentZero Age Main Sequence (ZAMS) fitting method, we also re-define thedistance to the cluster to be 246 pc.
| 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.
| Photometric study of Zeta SCULPTORIS cluster
Photographic photometry of about 1500 stars in the region of the ZetaSculptoris cluster has been accomplished, and relations between thisphotometry and broad- and intermediate-band photoelectric photometryestablished. From observation of the H-R diagrams, it is concluded thatabout 150 stars belong to the unevolved main sequence of the cluster. Asmall reddening of E(B - V) = 0.013 m similar to values given by otherauthors, and a mean modulus of about 6.9 mag, have been determined. Twogaps exist in the main sequence, one between (B - V) about 0.06 m andabout 0.30 m and the other around (B - V) about 1.00.
| 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
| 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
| 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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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Scultore |
| Ascensione retta: | 00h06m55.76s |
| Declinazione: | -30°36'11.0" |
| Magnitudine apparente: | 10.282 |
| Moto proprio RA: | 21.3 |
| Moto proprio Dec: | 6.3 |
| B-T magnitude: | 10.639 |
| V-T magnitude: | 10.312 |
Cataloghi e designazioni:
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