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CNONa and 12C/13C in giant stars of 10 open clusters
Context: Evolved low-mass stars (0.8 ≤ M/Mȯ ≤ 2.5)of a wide range of metallicity bear signatures of a non-standard mixingevent in their surface abundances of Li, C, and N, and in their12C/13C ratio. A Na overabundance has also beenreported in some giants of open clusters but remains controversial. Thecause of the extra-mixing has been attributed to thermohaline convectionthat should take place after the RGB bump for low-mass stars and on theearly-AGB for more massive objects. Aims: To track the occurrenceof this process over a wide mass range, we derive in a homogeneous waythe abundances of C, N, O, and Na, as well as the12C/13C ratio in a sample of 31 giants of 10 openclusters with turn-off masses from 1.7 to 3.1 Mȯ. Thesample includes red giants, clump giants, and early-AGB stars. We studythe observational behavior of the abundances as well as the possiblecorrelations between different elements and between the chemicalabundances and stellar mass. Methods: A model atmosphereanalysis is conducted using high signal-to-noise ratio, high-resolutionFEROS and EMMI spectra. We derive atmospheric parameters using Fe i andFe ii lines. We calculate abundances for Na, C, N, and O, as well as the12C/13C ratio using spectral synthesis. For theelements Mg, Ca, Si, Sc, Ti, V, Cr, Co, and Ni, abundances are derivedusing equivalent widths. Results: A group of first ascent redgiants with M/Mȯ ≤ 2.5 exhibits lower [N/C] ratiosthan those measured in clump giants of the same mass range, suggestingan additional increase in the [N/C] ratio after the first dredge-up. Thesodium abundances corrected from NLTE are found to be about solar.[Na/Fe] shows a slight increase of 0.10 dex as a function of stellarmass in the 1.8 to 3.2 Mȯ range covered by our sample,in agreement with standard first dredge-up predictions. Our results donot support previous claims of sodium overabundances as high as +0.60dex. An anti-correlation between 12C/13C andturn-off mass is identified and interpreted as being caused by apost-bump thermohaline mixing. Moreover, we find low12C/13C ratios in a few intermediate-massearly-AGB stars, confirming that an extra-mixing process also operatesin stars that do not experienced the RGB bump. In this case, theextra-mixing possibly acts on the early-AGB, in agreement withtheoretical expectations for thermohaline mixing.Observations collected at ESO, La Silla, Chile (programmes 56.A-0285 and65.L-0026A).Tables 1, 3, 6 and 7 are only available in electronic form athttp://www.aanda.orgTable A.1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/267
| Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters
Context: Radial velocities have proved to be an efficient method formembership determination if there are at least 2 or 3 red giants in acluster. They are necessary for galactic studies, but are still missingfor many open clusters. Aims: We present the final catalogues of along-term observing programme performed with the two coravelspectrovelocimeters for red giants in open clusters. The main aims wereto detect spectroscopic binaries and determine their orbital parameters,determine the membership, and compute mean velocities for the stars andopen clusters. Methods: We computed weighted mean radial velocities for1309 stars from 10 517 individual observations, including the systemicradial velocities from spectroscopic orbits and for cepheids. Results:The final results are contained in three catalogues collecting 10 517individual radial velocities, mean radial velocities for 1309 redgiants, and mean radial velocities for 166 open clusters among whichthere are 57 new determinations. We identified 891 members and 418non-members. We discovered a total of 288 spectroscopic binaries, amongwhich 57 are classified as non-members. In addition 27 stars were judgedto be variable in radial velocities and they are all red supergiants. Conclusions: The present material, combined with recent absolute propermotions, will permit various investigation of the galactic distributionand space motions of a large sample of open clusters. However, thedistance estimates still remain the weakest part of the necessary data.This paper is the last one in this series devoted to the study of redgiants in open clusters based on radial velocities obtained with thecoravel instruments.Based on observations collected at the Haute-Provence Observatory(France) and on observations collected with the Danish 1.54-m telescopesat the European Southern Observatory, La Silla, Chile. Full Tables [seefull textsee full textsee full textsee full textsee full text] to [seefull textsee full textsee full textsee full textsee full text] are onlyavailable and Tables [see full textsee full textsee full textsee fulltextsee full text] and [see full textsee full textsee full textsee fulltextsee full text] are also 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/485/303
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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/.
| 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
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| 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
| Open cluster chemical composition. 1: Later type stars in eight clusters
Abundance analyses of 36 stars associated with eight open clusters (IC2581, NGC 3532, NGC 5822, NGC 6067, NGC 6087, IC 4725 (M25), IC 4756,and NGC 6882/6885) are presented. The stars are primarily evolved G andK giants and supergiants. Cepheids in NGC 6067, NGC 6087, and IC 4725are included as are non-cluster Cepheids near the clusters NGC 3532, NGC6067, and IC 4725. With the addition of a background K giant in IC 4725,the total number of stars is 40. Elemental abundances derived includeLi, C, N, O, the alpha-elements, the Fe peak, and limited data on theheavy elements. The Na abundances of the sample show a gravitydependence in the sense of an increase in the abundance as the gravitydecreases. The CNO abundances indicate that these objects are processed(on the whole), and that they show the O deficiency previously noted inintermediate mass stars by Luck & Lambert (1981, 1985). There arefour stars in the sample which appear to be unprocessed: two giants andtwo supergiants. There are also two super-Li stars in the sample, one ofwhich is most likely a weak G-band star. It is suggested that thesuper-Li F supergiants could be evolved blue stragglers. The moststriking result of the study is the finding that the (O/Na) ratiocorrelates strongly with the gravity and the stellar mass, thus implyingthat there is a nonstandard additional mixing process affecting thesurface abundances of these stars. A promising candidate for the mixingprocess is the turbulent diffusive mixing process proposed byDenissenkov (1993) which brings Na to the surface and which could alsolead to a modification of the oxygen content.
| A photometric analysis of the intermediate-age open cluster NGC 5822
The study presents photoelectric photometry of stars in NGC 5822 on theUBVR and DDO systems. The BV data are employed to calibrate aphotographic survey of the cluster, while UBV and DDO data are used toconstrain the cluster reddening and metallicity. Taken in conjunctionwith previous photometric analysis, it is found that the cluster has areddening of 0.15 +/- 0.015 (pe) as defined for the stars at theturnoff, and a metallicity relative to the sun of -0.15 +/- 0.05 (pe).Comparisons to isochrones without convective overshoot indicate an ageof 1.25 x 10 exp 9 yr and are generally in agreement with observation ifthe scatter near the turnoff results from a combination of a modesthydrogen-exhaustion hook, binaries, and field-star contamination. It isshown that when isochrones of the appropriate metallicity areconsistently normalized, the nonovershoot models do not adequately matchthe observations of intermediate-age clusters in that they cannotreproduce the shape of the CMD or the distribution of stars near theturnoff, nor do they predict the apparent trend of luminosity with agefound for the red giant clump.
| Metallicities and radial velocities of old open clusters
Medium resolution spectra of giant stars in 24 open clusters with agesgreater than about 1 Gyr have been obtained and analyzed to provideradial velocities accurate to 10-15 km/s and (Fe/H) metallicitiesaccurate to 0.15 dex. The radial velocities of the older cluster systemsare consistent with those expected from the reflex of solar motion andsimple Galactic rotation. The cluster kinematics suggest strongly thatthey are drawn from the old thin disk stellar population. An abundancegradient in the Galactic disk of -0.09 +/- 0.02 dex/kpc is found. Thisgradient is in good agreement with that found for samples of youngeropen clusters, suggesting that there has been little change in theGalactic radial abundance gradient over time. The cluster sample showsno correlation between age and metallicity, regardless of Galactocentricradius. The clusters show an unexpected correlation between the Mg linestrength and age of the cluster at a fixed metallicity. Possible reasonsfor this are discussed.
| Red giants in open clusters. III - Binarity and stellar evolution in five intermediate-age clusters: NGC 2360, 2423, 5822, 6811, and IC 4756
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&A...237...61M&db_key=AST
| Yellow evolved stars in open clusters
This paper describes a program in which Galactic cluster post-AGBcandidates were first identified and then analyzed for clustermembership via radial velocities, monitored for possible photometricvariations, examined for evidence of mass loss, and classified ascompletely as possible in terms of their basic stellar parameters. Theintrinsically brightest supergiants are found in the youngest clusters.With increasing cluster age, the absolute luminosities attained by thesupergiants decline. It appears that the evolutionary tracks ofluminosity class II stars are more similar to those of class I than ofclass III. Only two superluminous giant star candidates are found inopen clusters.
| New photometric data for the red giants in the open cluster NGC 5822 - Membership, chemical composition and physical properties
New photoelectric UBV, DDO, and CMT1T2 data of 14G and K stars in the field of the open cluster NGC 5822 are presented.By applying two independent photometric criteria 11 stars are found tohave a high probability of being cluster giants, while three remainingstars are almost certainly red field objects. A reddening E(B-V) =0.15±0.01, a distance modulus of V0-MV =8.77±0.18, and an age of about 6 - 8×108yr havebeen derived. NGC 5822 has a mean ultraviolet excess of ?(U-B) =0.00±0.01, with respect to the field K giants, and a meancyanogen anomaly of ?CN = +0.031±0.008, both implying anearly solar iron abundance. The effective temperatures, surfacegravities and masses of the red giants have also been determined.
| DDO photometry of giants in four southern open clusters
Results are presented for photoelectric photometry in the DDOintermediate-band system of G and K giants in the very old open clusterMelotte 66 and the old clusters NGC 4349, 5822, and 5823. Averagereddenings, corrected mean distance moduli, and mean cyanogen anomaliesare derived for the giants in these clusters, and several peculiar starsare identified. The results indicate that: (1) the giants in Melotte 66are deficient in CN (and therefore in metallicity) relative to nearby Kgiants; (2) there is no evidence for a change in overall CN strengthbetween the giant and horizontal branches of Melotte 66; (3) NGC 4349and 5822 appear slightly richer in metals than nearby K giants; (4) NGC5823 does not constitute a coherent sample of giants and is likely to beaffected by considerable field-star contamination; and (5) there is onlymarginal evidence for a physical association between NGC 5822 and 5823.
| UBV photometry of the southern open cluster NGC 5822.
Abstract image available at:http://adsabs.harvard.edu/abs/1974RMxAA...1...89B
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Datos observacionales y astrométricos
| Constelación: | Lobo |
| Ascensión Recta: | 15h04m02.25s |
| Declinación: | -54°20'21.0" |
| Magnitud Aparente: | 9.112 |
| Movimiento Propio en Ascensión Recta: | -6.5 |
| Movimiento Propio en Declinación: | -5.7 |
| B-T magnitude: | 10.652 |
| V-T magnitude: | 9.24 |
Catálogos y designaciones:
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