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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
| Photometric membership and metallicities of red giant candidates in selected open clusters
As part of a long-term project to determine abundances andastrophysical properties of evolved red stars in open clusters, wepresent high-precision DDO photoelectric observations for a sample of 33red giant candidates projected in the fields of nine Galactic openclusters. These data are supplemented with U BV photoelectric photometryof 24 of these stars as well as with CORAVEL radial-velocityobservations for 13 red giant candidates in four of the clusters. Wealso present Washington photoelectric photometry of a small sample ofred giant candidates of the open cluster Ruprecht 97. The likelihood ofcluster membership for each star photometrically observed and for 23additional red giant candidates with U BV and DDO data available in theliterature, is evaluated by using two independent photometric criteria.Nearly 82% of the analysed stars are found to have a high probability ofbeing cluster giants. Photometric membership probabilities show verygood agreement with those obtained from CORAVEL radial velocities. WhileE(B-V) colour excesses were determined from combined B-V and DDOcolours, calibrations of the DDO system were used to derive MK spectraltypes, effective temperatures and metallicities.The derived DDOmetallicities range between values typical of moderately metal-poorclusters ([Fe/H] = -0.19) to moderately metal-rich ([Fe/H] = 0.25) ones.Tables 3, 4, 7-9 are available at the CDS viahttp://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/AN/329.609
| 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
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| 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
| Chemical abundances in seven red giants of NGC 2360 and NGC 2447
Chemical abundances of about fifteen elements from oxygen to europiumare measured in seven red giants of the two open clusters NGC 2360 andNGC 2447. The effective temperatures of the giants are determinedspectroscopically by taking advantage of their known masses (~ 2Msolar in NGC 2360 and ~ 3 Msolar in NGC 2447) andbolometric magnitudes. The average iron abundances we obtain for the twoclusters are [Fe/H]=0.07 for NGC 2360 and [Fe/H]=0.03 for NGC 2447.Evolutionary stellar model calculations are performed in the mass range1 - 4 Msolar in order to analyze the surface Na and Oabundances predicted after the first dredge-up. The sodium abundanceshows a well defined correlation with stellar mass in the 2 - 3Msolar range. The agreement between our Na abundancedeterminations in NGC 2360 and our model predictions at 2Msolar is very good. In contrast, the overabundance in one ofthe three stars in NGC 2447 exceeds that predicted at 3Msolar by ~ 0.08 dex, which is significant compared to theobservational error bars. The effects of core overshooting, convectionprescription, metallicity and nuclear reaction rates on the Na surfacepredictions of our models are investigated. An oxygen deficiencyrelative to iron by 0.2 dex is measured in our stars, in disagreementwith our model predictions. Assuming that the Sun is 0.1-0.3 dexenriched in oxygen relative to neighbor stars could explain thediscrepancy. Based on observations collected at the European SouthernObservatory, La Silla, Chile (period 56) Table 3 is available only 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
| Washington photometry of open cluster giants - Nine old disk clusters in the third Galactic quadrant
Washington photoelectric photometry for 136 stars in nine old openclusters is presented and used to determine the luminosity class, T(e),and metallicity. The virtually unstudied cluster NGC 2324 is found tohave a metallicity one tenth that of the sun, as is the cluster NGC 2660for which previous estimates have ranged from about +0.1 to -0.5. Athird cluster, NGC 3960, with a Galactocentric distance of only 8 kpc,is found to have a metallicity of -0.7, also substantially lower thanpublished values. Such clusters indicate that substantial scatteractually exists in the tight relation found by Friel and Janes (1992)between the metallicity of an open cluster and its currentGalactocentric distance. Outer disk clusters have a metallicity at agiven age that is much more like that of the LMC counterparts than thatof solar neighborhood disk field stars or clusters.
| 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
| Kataloge photographischer und photoelektrischer Helligkeiten von 25 galaktischen Sternhaufen im RGU- und UcBV-System
Not Available
| The color excesses and metallicities of the open clusters NGC 2360 and NGC 3680
Abstract image available at:http://adsabs.harvard.edu/abs/1972ApJ...172..615M
| The Intermediate-Age Cluster NGC 2360
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...152...83E&db_key=AST
| Dreifarbenphotometrie in offenen Sternhaufen sowie in zwei Sternfeldern im Cyg.
Not Available
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| Sað Açýklýk: | 07h17m35.06s |
| Yükselim: | -15°38'35.5" |
| Görünürdeki Parlaklýk: | 10.801 |
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