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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
| Na, Al, and O Abundances of Open Clusters NGC 7142, NGC 6939, and IC 4756
We present an analysis of echelle spectra of stars in three openclusters obtained with the Hydra multiobject spectrograph on the WIYN3.5 m telescope. Abundances of Fe, O, Si, Ca, Na, Al, and Ni have beendetermined via equivalent width analysis and spectrum synthesis. Meanabundances for each cluster are compared to those of previous studiesand of other clusters in the literature, with emphasis on exploring theenhancements of Na and Al seen in many open clusters. All three clustersshow enhanced values of [Na/Fe] and [Al/Fe], while the abundances of Fe,O, Si, and Ca are consistent with their ages and locations in theGalactic disk.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| 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
| ROSAT HRI observations of the intermediate-age open cluster IC 4756
We have obtained an 88 kilosecond ROSAT HRI exposure of theintermediate-age open cluster IC 4756 with the purpose of detectingstars in the high luminosity tail (log L_X >= 10(29) erg s(-1) ) ofits X-ray luminosity distribution. However, only 1 cluster member (HSS201) out of the 60 members inside the central high-sensitivity region ofthe HRI field of view (FOV) was detected. This star has spectral typeA8, suggesting a close binary system with a low mass X-ray emittingcompanion. We compare the distribution of upper limits for F and G-typedwarfs in IC 4756 with the X-ray distribution functions of the similarlyaged Hyades and Praesepe clusters. The results of this statisticalanalysis are inconclusive for G-type stars, but suggest that at leastF-type stars in IC 4756 are not as X-ray luminous as their Hyadescounterparts, thus indicating intrinsic differences between the twoclusters. Finally, our data indicate a deficit of very active binarieswith respect to both Hyades and Praesepe, and older open clusters.
| Amendment of our method for deriving stellar membership of an open cluster
Our method for determining statistically the members of an open clusterby means of the proper motions (Missana et al.) is amended and itsvalidity is verified by applying it to the cluster IC 4756 with the datagiven by Herzog et al. (1975), adding nothing to their results. In thecomputation of the dispersion ellipses of the samples and of theChi2 for deriving the significance levels, the weights of theproper motions have been taken into account. The results obtained by thecriterion of the Chi2 and those obtained by Herzog et al. bythe criterion of the maximum likelihood of Sanders (1971) areconcordant.
| Metallicities and velocities of old open clusters
We have obtained moderate-resolution CCD spectra for giants in six oldopen clusters in the direction of the galactic anticenter. Usingcross-correlation techniques, we determined radial velocities for starsin each cluster and used these values to compute a cluster mean accurateto approximately 10 km/s. These means agree quite well with publishedvalues. We then used between four and six spectroscopic indices tomeasure the metallicity of each star and produce a mean clustermetallicity. Following the Galactic metallicity gradient, more distantclusters are metal poor compared with clusters closer to the solarneighborhood. We used our data, which are centered around the solarradius, to supplement published results by Friel and Janes (1993, A&A,267, 75), and used the combined data set to better define the Galacticmetallicity gradient. We found that Delta (Fe/H) Delta Rgc =-0.097 +/- 0.017 dex/kpc for Rgc greater than 7 kpc. Thisresult agrees quite well with that of Friel and Janes and with that ofother authors. We discuss a possible correlation between age and Mgenhancement which is indicated by the differences between Fe and Mg linestrength among cluster giants. We also briefly consider metallicitydependences with age and height above the Galactic plane.
| 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
| Carbon isotope ratios and lithium abundances in open cluster giants
New high-resolution, high S/N spectra of CN lines at 8000 A and Li linesat 6707 A have been obtained for giants in about 20 Galactic openclusters and C-12/C-13 ratios and Li abundances determined for thesestars. The ages of the clusters vary from about 50 million years to 5billion years, and their turn-off masses vary from 1 solar mass to about6 solar masses. The ages and turn-off masses were determined by fittingtheoretical isochrones to the cluster color-magnitude diagrams.Correlation of the isotope ratio and the Li abundances with the clusterturn-off masses indicates the following: (1) the C-12/C-13 ratioincreases steeply with the turn-off mass until a mass of approximately2.2 solar masses when the ratio levels off abruptly to a value near 26;(2) older clusters with turn-off masses lower than about 2.2 solarmasses in general exhibit C-12/C-13 ratios that are considerably lowerthan the theoretically predicted values while those with larger turn-offmasses show ratios close to standard predictions; and (3) no strongcorrelation exists between the Li abundances and the cluster turn-offmass, and the Li abundances in giants are, in general, lower thantheoretically predicted values. Various theories to explain the observedabundance trends are discussed.
| A four-color and Hbet study of the galactic cluster IC 4756.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..157S&db_key=AST
| Membership and photometry of the open cluster IC 4756
Probabilities of membership, based on relative proper motions, for 464stars in the field of IC 4756 are given. The cluster proper motiondispersion (m.e.) of 0.09 sec of arc yields 173 probable members.Photographic UBV magnitudes of 471 stars in the field are presented. Thecolor excess of IC 4756 is E(B-V) equal to 0.19 min; the apparentdistance modulus equals 8.5 min, corresponding to the true distance of400 pc. The membership probabilities of 6 blue stragglers and of thesupergiant HD 172365 (F9 Ib) are discussed.
| Untersuchung der offenen Sternhaufen IC 4665, NGC 6633, IC 4756
Not Available
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| קבוצת-כוכבים: | נחש |
| התרוממות ימנית: | 18h38m52.93s |
| סירוב: | +05°20'16.5" |
| גודל גלוי: | 9.04 |
| תנועה נכונה: | 1 |
| תנועה נכונה: | -1.5 |
| B-T magnitude: | 10.471 |
| V-T magnitude: | 9.159 |
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