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Chemical composition of evolved stars in the open cluster IC 4651
We present an analysis of high-resolution spectra of threecore-helium-burning 'clump' stars and two first ascent giants in theopen cluster IC 4651. Atmospheric parameters (Teff, log g,vt and [Fe/H]) were determined in our previous study byCarretta et al. In this study, we present abundances of C, N, O and upto 24 other chemical elements. Abundances of carbon were derived usingthe C2 Swan (0, 1) band head at 5635.5 Å. Thewavelength interval 7980-8130 Å, with strong CN features, wasanalysed in order to determine nitrogen abundances and12C/13C isotope ratios. The oxygen abundances weredetermined from the [O I] line at 6300 Å. Compared with the Sunand other dwarf stars of the Galactic disc, mean abundances in theinvestigated clump stars suggest that carbon is depleted by about 0.3dex, nitrogen is overabundant by about 0.2 dex and oxygen is close tosolar. This has the effect of lowering the mean C/N ratio to 1.36± 0.11. The mean 12C/13C ratios are loweredto 16 ± 2. Other investigated chemical elements have abundanceratios close to the solar ones. a Star numbers, V and B-Vfrom Lindoff (1972).
| The PASTEL catalogue of stellar parameters
Aims: The PASTEL catalogue is an update of the [Fe/H] catalogue,published in 1997 and 2001. It is a bibliographical compilation ofstellar atmospheric parameters providing (T_eff, log g, [Fe/H])determinations obtained from the analysis of high resolution, highsignal-to-noise spectra, carried out with model atmospheres. PASTEL alsoprovides determinations of the one parameter T_eff based on variousmethods. It is aimed in the future to provide also homogenizedatmospheric parameters and elemental abundances, radial and rotationalvelocities. A web interface has been created to query the catalogue onelaborated criteria. PASTEL is also distributed through the CDS databaseand VizieR. Methods: To make it as complete as possible, the mainjournals have been surveyed, as well as the CDS database, to findrelevant publications. The catalogue is regularly updated with newdeterminations found in the literature. Results: As of Febuary2010, PASTEL includes 30151 determinations of either T_eff or (T_eff,log g, [Fe/H]) for 16 649 different stars corresponding to 865bibliographical references. Nearly 6000 stars have a determination ofthe three parameters (T_eff, log g, [Fe/H]) with a high qualityspectroscopic metallicity.The catalogue can be queried through a dedicated web interface at http://pastel.obs.u-bordeaux1.fr/.It is also available in electronic form at the Centre de DonnéesStellaires in Strasbourg (http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/pastel),at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/515/A111
| Open Clusters as Galactic Disk Tracers. I. Project Motivation, Cluster Membership, and Bulk Three-Dimensional Kinematics
We have begun a survey of the chemical and dynamical properties of theMilky Way disk as traced by open star clusters. In this firstcontribution, the general goals of our survey are outlined and thestrengths and limitations of using star clusters as a Galactic disktracer sample are discussed. We also present medium-resolution (R ~ 15,0000) spectroscopy of open cluster stars obtained with the Hydramulti-object spectrographs on the Cerro Tololo Inter-AmericanObservatory 4 m and WIYN 3.5 m telescopes. Here we use these data todetermine the radial velocities of 3436 stars in the fields of openclusters within about 3 kpc, with specific attention to stars havingproper motions in the Tycho-2 catalog. Additional radial velocitymembers (without Tycho-2 proper motions) that can be used for futurestudies of these clusters were also identified. The radial velocities,proper motions, and the angular distance of the stars from clustercenter are used to derive cluster membership probabilities for stars ineach cluster field using a non-parametric approach, and the clustermembers so identified are used, in turn, to derive the reliable bulkthree-dimensional motion for 66 of 71 targeted open clusters. Thehigh-probability cluster members that we identify help to clarify thecolor-magnitude sequences for many of the clusters, and are primetargets for future echelle resolution spectroscopy as well asastrometric study with the Space Interferometry Mission (SIMPlanetquest).
| 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
| Iron abundances from high-resolution spectroscopy of the open clusters NGC 2506, NGC 6134, and IC 4651
This is the first of a series of papers devoted to deriving themetallicity of old open clusters to study the time evolution of thechemical abundance gradient in the Galactic disk. We present detailediron abundances from high resolution (R⪆ 40 000) spectra of severalred clump and bright giant stars in the open clusters IC4651, NGC 2506 and NGC6134. We observed 4 stars of NGC 2506, 3 stars of NGC 6134 and5 stars of IC 4651 with the FEROS spectrograph with the ESO 1.5 mtelescope; moreover, 3 other stars of NGC 6134 were observed with theUVES spectrograph on Kueyen (VLT UT2). After excluding the cool giantsnear the red giant branch tip (one in IC 4651 and one in NGC 2506), wefound overall [Fe/H] values of -0.20±0.01, rms = 0.02 dex (2stars) for NGC 2506, +0.15±0.03, rms = 0.07 dex (6 stars) for NGC6134 and +0.11±0.01, rms = 0.01 dex (4 stars) for IC 4651. Themetal abundances derived from a line analysis for each star wereextensively checked using spectrum synthesis of about 30 to 40 Fe Ilines and 6 Fe II lines. Our spectroscopic temperatures providereddening values in good agreement with literature data for theseclusters, strengthening the reliability of the adopted temperature andmetallicity scale. Also, gravities from the Fe equilibrium of ionizationagree quite well with expectations based on cluster distance moduli andevolutionary masses.Based on observations collected at ESO telescopes under programme65.N-0286, and in part 169.D-0473.
| Critical tests of stellar evolution in open clusters. III. Stellar population and dynamical evolution of IC 4651
We present multiple-epoch radial-velocity observations for 104 stars ina 10arcmin x 10arcmin field of the intermediate-age open cluster IC 4651to V ~ 14.5. Only 13 stars (13%) of the full sample are field stars.From the 44 single member stars we find a mean radial velocity of-30.76+/-0.20 km s-1, and the 12 single red-giant membersyield a true radial-velocity dispersion of 0.74 km s-1. Ofthe 19 giant members, 7 (37%) are spectroscopic binaries with periods upto 5000 days, while 35 (52%) of the 67 main-sequence and turnoff membersare binaries with periods less than ~ 1000 days. Combined with our deep,accurate CCD Strömgren photometry in a ~ 21arcminx21 arcmin fieldof IC 4651 \citep{mei00}, these data substantially improve thedefinition of the cluster locus in the colour-magnitude diagram and thespatial structure of the cluster, although the photometry shows that IC4651 contains at least twice as many stars on the upper main sequence aswas believed when the radial-velocity survey was initiated. The singlecluster members define a very tight sequence in the CMD, and two sets ofisochrones from stellar models with convective overshooting (d/H_p =0.2) have been fit to it. Our best estimate for the age of IC 4651 is1.7 +/- 0.15 Gyr, assuming [Fe/H] = 0.12 (Hyades) and E(b-y)= 0.071. Including the ~ 650 stars newly discovered from the photometry,we estimate the present total mass of IC 4651 to be ~ 630Msun, excluding any undetected stellar remnants. Thecorresponding tidal cutoff radius is ~ 22arcmin . IC 4651 shows evidenceof moderate mass segregation: Most of the turn-off stars and nearly allthe red giants are located at radii smaller than ~ 7arcmin , while thelower main-sequence stars are less centrally concentrated. The spatialdistributions of cluster and field stars indicate that additionalcluster stars are probably still to be found outside the fields studiedso far. Comparison of the present mass function of IC 4651 withplausible initial mass functions indicates that the cluster initiallycontained at least ~ 8300 stars with a total mass of ~ 5300Msun. Thus, of the original cluster stars only ~ 7%,containing ~ 12% of the initial mass, remain today. Of the initialcluster mass, ~ 35% has been lost due to evolution of the most massivestars into white dwarfs or other remnants while the remaining ~ 53%,comprising ~ 93% of the original low-mass stars, appear to have migratedout of the observed field or been lost from the cluster altogether. IC4651 is currently 1 kpc closer to the Galactic center than its``sister'' cluster NGC 3680 \citep{nordstrom97}, but their Galacticorbital parameters indicate that the mean orbital radius of IC 4651 isin fact larger by 0.7 kpc, providing a plausible reason why it is muchless advanced in its dynamical evolution than the coeval cluster NGC3680. Based on observations obtained with the Danish 1.5-m telescope atthe European Southern Observatory, La Silla, Chile. Tables 1 and 2 arealso, and Table A1 only, 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/386/187
| 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
| Ca II activity and rotation in F-K evolved stars
Ca II H and K high resolution observations for 60 evolved stars in thefield and in 5 open clusters are presented. From these spectrachromospheric fluxes are derived, and a homogeneous sample of more than100 giants is built adding data from the literature. In addition, formost stars, rotational velocities were derived from CORAVELobservations. By comparing chromospheric emission in the cluster starswe confirm the results of Pasquini & Brocato (1992): chromosphericactivity depends on the stellar effective temperature, and mass, whenintermediate mass stars (M ~ 4 Msun) are considered. TheHyades and the Praesepe clump giants show the same level of activity, asexpected from stars with similar masses and effective temperatures. Adifference of up to 0.4 dex in the chromospheric fluxes among the Hyadesgiants is recorded and this sets a clear limit to the intrinsic spreadof stellar activity in evolved giants. These differences in otherwisevery similar stars are likely due to stellar cycles and/or differencesin the stellar initial angular momentum. Among the field stars none ofthe giants with (V-R)o < 0.4 and Ia supergiants observedshows a signature of Ca II activity; this can be due either to the realabsence of a chromosphere, but also to other causes which preclude theappearance of Ca II reversal. By analyzing the whole sample we find thatchromospheric activity scales linearly with stellar rotational velocityand a high power of stellar effective temperature: F'k ~Teff7.7 (Vsini)0.9. This result can beinterpreted as the effect of two chromospheric components of differentnature: one mechanical and one magnetic. Alternatively, by using theHipparcos parallaxes and evolutionary tracks, we divide the sampleaccording to the stellar masses, and we follow the objects along anevolutionary track. For each range of masses activity can simply beexpressed as a function of only one parameter: either theTeff or the angular rotation Omega , with laws F'k~ Omega alpha , because angular velocity decreases witheffective temperature along an evolutionary track. By using theevolutionary tracks and the observed Vsini we investigate the evolutionof the angular momentum for evolved stars in the range 1-5Msun. For the 1.6-3 solar mass stars the data are consistentwith the IOmega =const law while lower and higher masses follow a lawsimilar to IOmega 2=const, where I is the computed stellarmomentum of inertia. We find it intriguing that Vsini remains almostconstant for 1Msun stars along their evolution; if a similarbehavior is shared by Pop II stars, this could explain the relativelyhigh degree of activity observed in Pop II giants. Finally, through theuse of models, we have verified the consistency of the F'k ~Omega alpha and the IOmega beta = Const lawsderived, finding an excellent agreement. This representation, albeitcrude (the models do not consider, for instance, mass losses) representsthe evolution of Ca II activity and of the angular momentum in asatisfactory way in most of the portion of HR diagram analyzed.Different predictions could be tested with observations in selectedclusters. Based on observations collected at ESO, La Silla. Tables 1-3are only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| New color-magnitude diagram for the open cluster IC 4651. Deep Strömgren uvby CCD photometry in a large field
New accurate CCD photometry in the u, v, b and y bands of theStrömgren system filters has been obtained for 17640 stars to V ~20m in a ~ 21 ' x 21' field centered onthe intermediate-age open cluster IC 4651. The resulting color-magnitudediagram (CMD) is substantially improved in completeness and accuracycompared to previous studies of IC 4651. Specifically, this study has:1) more than doubled the known size of the cluster area on the sky, 2)more than doubled the number of stars brighter than V ~ 14m,3) added 160 ``new" candidate member stars to the turn-off region of theCMD, 4) identified ~ 600 fainter stars that trace a previouslyundetected and well-defined main-sequence down to V ~ 18m,and 5) enabled a very accurate determination of true distance modulus((m-M)0 = 10.03 +/- 0.1) by fitting the Hyades main-sequenceover the long stretch of the cluster main-sequence. The (v-y) - V CMDdefines the main-sequence significantly better than the traditional(b-y) or (B-V) CMDs. These findings make IC 4651 a perfect target fortesting stellar evolution models. A correlation is found between the CMDand the radial distance of the stars to the cluster center. The faintermain-sequence stars are less centrally concentrated, as predicted bytheory. Overall, IC 4651 appears to be a moderately dynamically evolvedcluster ideally suited for testing of dynamical models. Based onobservations obtained with the Danish 1.5-m telescope at the EuropeanSouthern Observatory, La Silla, Chile. Tables 1, 2 and 3 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| CCD UVBY Hβ Photometry in Clusters. I. The Open Cluster Standard, IC 4651
CCD photometry of the intermediate-age open cluster IC 4651 on theuvbyHβ system is presented and analyzed. By using a combination ofthe information from the color-magnitude diagram (CMD) and thecolor-color diagrams, a sample of 98 highly probable main-sequencecluster members with high photometric accuracy is isolated. From thissample, adopting the intrinsic color relation of Olsen,E(b-y)=0.062+/-0.003 and [Fe/H]=+0.077+/-0.012, where the errors quotedare the standard errors of the mean and refer to the internal errorsalone. Use of the Nissen intrinsic color relation produces E(b-y)=0.071and [Fe/H]=+0.115. Adopting the lower reddening, a direct main-sequencefit to the Hyades with (m-M)=3.33 leads to (m-M)=10.15, while isochroneswith convective overshoot and zeroed to the Hyades produce an age of1.7+/-0.1 Gyr, with an excellent match to the morphology of the turnoff.The higher reddening produces (m-M)=10.3 and an age lower by 0.1 Gyr.Comparison with the CMD of NGC 3680 shows that the two clusters havevirtually identical morphology, which in combination with their similarcompositions produces identical ages. Coincidentally, the shifts in theCMD necessary to superpose the two clusters require that the apparentmoduli of IC 4651 and NGC 3680 be the same, whileE(b-y)4651=E(b-y)3680+0.04.
| Red giants in open clusters. IV. NGC 3680 and IC 4651.
Radial-velocity observations of 35 red giants in the field of theintermediate-age open clusters NGC 3680 and IC 4651 are presented andanalysed for membership and duplicity. Five stars in NGC 3680 and one inIC 4651 were identified as non-members, and six and five spectroscopicbinaries, respectively, were discovered among the red giant members inthe two clusters. Orbits have been determined for seven of the binaries,four of which are still preliminary. The mean cluster velocities of NGC3680 and IC 4651 are 0.9+/-0.2km/s and -31.0+/-0.2km/s respectively. Themorphology of the red giant region in the colour magnitude diagramsshows a well-populated clump in both clusters. In both clusters, onecertain member star is clearly brighter and redder than the clump, whileIC 4651 shows, in addition, a probable concentration of stars on theascending giant branch.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| UvbyH-beta photoelectric and CCD photometry of IC 4651
An analysis of uvbyH-beta photoelectric and CCD photometry of IC4651shows a Fe/H abundance ratio of 0.23 + or - 0.02, an E(b-y) value of0.064 + or - 0.006, and an age on the system of VandenBerg (1985) of 2.4+ or - 0.2 x 10 to the 9th yr. Scatter noted in the clustercolor-magnitude diagram can be explained by binaries, nonmembers, and ablueward hook due to the hydrogen-exhaustion phase. The cluster turnoffindicates some evidence for the presence of bimodality which issuggested to be the result of nonstandard evolution near theBohm-Vitense gap.
| Astrophysical properties of red giants in three open clusters older than the Hyades
The application to the program stars of two independent membershipcriteria based on BV and DDO photometry makes it possible to distinguisha few red field stars from the physical members of the clusters. Inparticular, two stars previously thought to be members of NGC 3680 byEggen (1969) and McClure (1972) are found not to be physically connectedwith this cluster. It is also found that the cluster giants in NGC 2482and IC 4651 have CN strengths nearly identical with the Hyades giants,whereas NGC 3680 is considerably poorer in CN than the above clusters.Within the limits of the DDO photometry, no firm evidence is seen forany intrinsic differences in CN strength among the giants in the threeclusters. This result is valid for the clump stars at the blue end ofthe giant branch in NGC 3680 and IC 4651. Both CMT(1)T(2) and DDO datalend support to the conclusion that IC 4651 is on the metal-rich side ofthe distribution of intermediate and old open clusters. The mass resultsindicate that the clumps stars in NGC 3680 and IC 4651 could haveundergone mass loss before reaching their core burning phase ofevolution.
| DDO photometry of giants in the open cluster IC 4651
DDO photometry has been obtained for 14 stars in the open cluster IC4651. The reddening and distance modulus derived from these data are ingood agreement with the results obtained from UBV photometry by Eggen.The cluster appears to have a heavy-element abundance slightly less thanthat of the Hyades, although one giant shows an anomalously strong4216-A CN band comparable to those seen in the SMR giants. A comparisonis made between this star and CN-enhanced giants in eight other openclusters. It is suggested that the CN-strong phenomenon among opencluster giants is the result of nonstandard stellar evolution, theoccurrence of which is supported by the presence of blue stragglers infive out of the eight comparison clusters, as well as in IC 4651 itself.
| The Intermediate-Age Cluster IC 4651
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJ...166...87E&db_key=AST
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| Csillagkép: | Oltár |
| Rektaszcenzió: | 17h25m08.94s |
| Deklináció: | -49°53'57.1" |
| Vizuális fényesség: | 8.992 |
| Távolság: | 581.395 parszek |
| RA sajátmozgás: | -0.5 |
| Dec sajátmozgás: | -2 |
| B-T magnitude: | 11.106 |
| V-T magnitude: | 9.167 |
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