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Публикации по объекту
New catalogue of blue stragglers in open clusters
We present a catalogue of blue-straggler candidates in galactic openclusters. It is based on the inspection of the colour-magnitude diagramsof the clusters, and it updates and supersedesthe first version(Ahumada & Lapasset 1995). A new bibliographical search was made foreach cluster, and the resulting information is organised into twotables. Some methodological aspects have been revised, in particularthose concerning the delimitation of the area in the diagrams where thestragglers are selected.A total of 1887 blue-straggler candidates have been found in 427 openclusters of all ages, doubling the original number. The catalogued starsare classified into two categories mainly according to membershipinformation.The whole catalogue (Tables 8, 9, notes, and references) is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/789
| Kinematics of the Open Cluster System in the Galaxy
Absolute proper motions and radial velocities of 202 open clusters inthe solar neighborhood, which can be used as tracers of the Galacticdisk, are used to investigate the kinematics of the Galaxy in the solarvicinity, including the mean heliocentric velocity components(u1,u2,u3) of the open cluster system,the characteristic velocity dispersions(σ1,σ2,σ3), Oortconstants (A,B) and the large-scale radial motion parameters (C,D) ofthe Galaxy. The results derived from the observational data of propermotions and radial velocities of a subgroup of 117 thin disk young openclusters by means of a maximum likelihood algorithm are:(u1,u2,u3) =(-16.1+/-1.0,-7.9+/-1.4,-10.4+/-1.5) km s-1,(σ1,σ2,σ3) =(17.0+/-0.7,12.2+/-0.9,8.0+/-1.3) km s-1,(A,B) =(14.8+/-1.0,-13.0+/-2.7) km s-1 kpc-1, and (C,D) =(1.5+/-0.7,-1.2+/-1.5) km s-1 k pc-1. A discussionon the results and comparisons with what was obtained by other authorsis given.
| Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
Context: .About 5% of upper main sequence stars are permeated by astrong magnetic field, the origin of which is still matter of debate. Aims: . With this work we provide observational material to studyhow magnetic fields change with the evolution of stars on the mainsequence, and to constrain theory explaining the presence of magneticfields in A and B-type stars. Methods: . Using FORS1 inspectropolarimetric mode at the ESO VLT, we have carried out a survey ofmagnetic fields in early-type stars belonging to open clusters andassociations of various ages. Results: . We have measured themagnetic field of 235 early-type stars with a typical uncertainty of 100 G. In our sample, 97 stars are Ap or Bp stars. For thesetargets, the median error bar of our field measurements was 80 G.A field has been detected in about 41 of these stars, 37 of which werenot previously known as magnetic stars. For the 138 normal A and B-typestars, the median error bar was 136 G, and no field was detected in anyof them.
| Proper motion determination of open clusters based on the UCAC2 catalogue
We present the kinematics of hundreds of open clusters, based on theUCAC2 Catalogue positions and proper motions. Membership probabilitieswere obtained for the stars in the cluster fields by applying astatistical method uses stellar proper motions. All open clusters withknown distance were investigated, and for 75 clusters this is the firstdetermination of the mean proper motion. The results, including the DSSimages of the cluster's fields with the kinematic members marked, areincorporated in the Open Clusters Catalogue supported on line by ourgroup.
| Elemental Abundance Studies of CP Stars. The Silicon Stars HD 87240 and HD 96729
We compared elemental abundances of field and open cluster Ap Si stars.In particular, an analysis of the Ap Si stars HD 87240 and HD 96729 ispresented using an ATLAS9 model atmosphere and observational materialtaken with a REOSC echelle spectrograph attached to the Jorge Sahade2.15 m telescope at CASLEO. These chemically peculiar (CP) stars belongto the southern hemisphere open clusters NGC 3114 and NGC 3532,respectively. For HD 87240 and HD 96729, C is mostly solar, Mg and S areslightly underabundant, Si and Ca are overabundant by factors between1--10. Heavier elements are all overabundant, TiCrFe by factors of 10, SrYZr by factors between 100--1000 and rare earths by factors of 1000 or more.
| CCD-Δ a and BVR photometry of NGC 7296
The first CCD photometric investigation of the open cluster NGC 7296 upto now was performed within the narrow band Δ a photometricsystem, which enables us to detect peculiar objects. A deeperinvestigation of that cluster followed, using the standard BVR-Besselfilter set. The age and E(B-V) was determined independently to log t =8.0 ± 0.1 and 0.15 ± 0.02, respectively by using Δ aand broadband photometry. In total five Be/Ae objects and two metal-weakstars showing significant negative Δ a-values as well as oneclassical chemically peculiar star could be identified within thatintermediate age open cluster.Based on observations at the Hvar Observatory, University of Zagreb andthe Leopold-Figl Observatory for Astrophysics, University of Vienna.
| On the incidence of chemically peculiar stars in the Large Magellanic Cloud
With the aim to corroborate the result of a search for chemicallypeculiar stars in the Large Magellanic Cloud (LMC), we presentmeasurements obtained from CCD imaging of two fields, one containing ayoung open cluster (NGC 1711). While for the latter field, including itssurrounding we obtain a contribution of 3 per cent of chemicallypeculiar stars detectable by Δa photometry (i.e. the magneticobjects of this group), the second field yields about half of this valuein good accordance with Maitzen et al.'s finding for NGC 1866, thesurrounding field of which has been found to exhibit a very low value ofsuch stars (0.3 per cent). Thus, we are faced with the fact that ourincipient impression about a substantially lower appearance of magneticchemically peculiar stars in the LMC as compared to the Galaxy continuesto be valid. Most of the photometrically identified peculiar stars (fromtheir historical origin denominated Ap stars) are located in the domainof the B-type stars. However, this is a selection effect due to thelimiting magnitude of our observing conditions impeding the observationof fainter main-sequence stars. In addition to objects showing up aspositive deviators in Δa photometry, we also discuss nine starswhich appear opposite the main line of normal stars, and hence arenegative deviators. For most of them, the interpretation as emissionstars of B-type seems to be appropriate. The statistically relevantnumber of observations obtained so far in the LMC supports the view thatthe formation of magnetic peculiar stars has occurred there at asignificantly lower rate.
| Rights and wrongs of the Hipparcos data. A critical quality assessment of the Hipparcos catalogue
A critical assessment of the quality of the Hipparcos data, partlysupported by a completely new analysis of the raw data, is presentedwith the aim of clarifying reliability issues that have surfaced sincethe publication of the Hipparcos catalogue in 1997. A number of defectsin the data are identified, such as scan-phase discontinuities andeffects of external hits. These defects can be repaired when re-reducingthe raw data. Instabilities in the great-circle reduction process arerecognised and identified in a number of data sets. These resultedmainly from the difficult observing conditions imposed by the anomalousorbit of the satellite. The stability of the basic angle over themission is confirmed, but the connectivity between the two fields ofview has been less than optimal for some parts of the sky. Both arefundamental conditions for producing absolute parallaxes. Although thereis clear room for improvement of the Hipparcos data, the catalogue aspublished remains generally reliable within the quoted accuracies. Someof the findings presented here are also relevant for the forthcomingGaia mission.
| Astrophysical parameters of Galactic open clusters
We present a catalogue of astrophysical data for 520 Galactic openclusters. These are the clusters for which at least three most probablemembers (18 on average) could be identified in the ASCC-2.5, a catalogueof stars based on the Tycho-2 observations from the Hipparcos mission.We applied homogeneous methods and algorithms to determine angular sizesof cluster cores and coronae, heliocentric distances, mean propermotions, mean radial velocities, and ages. For the first time we derivedistances for 200 clusters, radial velocities for 94 clusters, and agesof 196 clusters. This homogeneous new parameter set is compared withearlier determinations, where we find, in particular, that the angularsizes were systematically underestimated in the literature.
| Searching for Planetary Transits in Galactic Open Clusters: EXPLORE/OC
Open clusters potentially provide an ideal environment for the searchfor transiting extrasolar planets, since they feature a relatively largenumber of stars of the same known age and metallicity at the samedistance. With this motivation, over a dozen open clusters are now beingmonitored by four different groups. We review the motivations andchallenges for open cluster transit surveys for short-period giantplanets. Our photometric monitoring survey of Galactic southern openclusters, the Extrasolar Planet Occultation Research/Open Clusters(EXPLORE/OC) project, was designed with the goals of maximizing thechance of finding and characterizing planets and of providing astatistically valuable astrophysical result in the case of nodetections. We use the EXPLORE/OC data from two open clusters, NGC 2660and NGC 6208, to illustrate some of the largely unrecognized issuesfacing open cluster surveys, including severe contamination by Galacticfield stars (>80%) and the relatively low number of cluster membersfor which high-precision photometry can be obtained. We discuss how acareful selection of open cluster targets under a wide range of criteriasuch as cluster richness, observability, distance, and age can meet thechallenges, maximizing chances to detect planet transits. In addition,we present the EXPLORE/OC observing strategy to optimize planetdetection, which includes high-cadence observing and continuouslyobserving individual clusters rather than alternating between targets.
| Deepsky delights.
Not Available
| Line Identification of the Si Star HD 87240
Line identifications are presented for the peculiar Apstar HD7240(δ = - 59° 51' 00.1'') in the spectral region λλ3710-5520. This object is a member of the southern open cluster NGC114.Comparison of this object with other field silicon stars shows that itshares many of their line anomalies.
| The star cluster Collinder 232 in the Carina complex and its relation to Trumpler 14/16
In this paper we present and analyze new CCD UBVRI photometry down toV≈21 in the region of the young open cluster Collinder 232, locatedin the Carina spiral arm, and discuss its relationship to Trumpler 14and Trumpler 16, the two most prominent young open clusters located inthe core of NGC 3372 (the Carina Nebula). First of all we study theextinction pattern in the region. We find that the total to selectiveabsorption ratio RV differs from cluster to cluster, being3.48±0.11, 4.16±0.07 and 3.73±0.01 for Trumpler 16,Trumpler 14 and Collinder 232, respectively. Then we derive individualreddenings and intrinsic colours and magnitudes using the method devisedby Romaniello et al. (\cite{Romaniello02}). Ages, age spreads anddistances are then estimated by comparing the Colour Magnitude Diagramsand the Hertzsprung-Russel diagram with post and pre-main sequencetracks and isochrones. We find that Trumpler 14 and Collinder 232 lie atthe same distance from the Sun (about 2.5 kpc), whereas Trumpler 16 liesmuch further out, at about 4 kpc from the Sun. As for the age, we findthat Trumpler 16 is older than both Trumpler 14 and Collinder 232. Forall the clusters we indicate the existence of a significant agedispersion, whose precise value is hampered by our inability to properlydistinguish members from non-members. We finally suggest that Collinder232 is a physical aggregate and provide estimates of its basicparameters.Based on observations taken at ESO La Silla.Tables 1 and 2 are 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/418/525
| New variable stars in open clusters. I. Methods and results for 20 open clusters
We present high precision CCD photometry of 1791 objects in 20 openclusters with an age of 10 Myr to 1 Gyr. These observations wereperformed within the Δ a photometric system which is primarilyused to detect chemically peculiar stars of the upper main sequence.Time bases range from 30 min up to 60 days with data from severalnights. We describe the time series analysis reaching a detection limitof down to 0.006 mag for apparent variability. In total, we havedetected 35 variable objects of which four are not members of theircorresponding clusters. The variables cover the entireHertzsprung-Russell diagram, hence they are interesting targets forfollow-up observations.Based on observations obtained at Complejo Astronómico elLeoncito (CASLEO), operated under the agreement between the ConsejoNacional de Investigaciones Científicas y Técnicas de laRepública Argentina and the National Universities of La Plata,Córdoba y San Juan; ESO-La Silla and UTSO-Las Campanas.
| CCD photometric search for peculiar stars in open clusters. V. NGC 2099, NGC 3114, NGC 6204, NGC 6705 and NGC 6756
We have investigated 1008 objects in the area of five intermediate ageopen clusters (NGC 2099, NGC 3114, NGC 6204, NGC 6705 and NGC 6756) viathe narrow band Δ a-system. The detection limit for photometricpeculiarity is very low (always less than 0.009 mag) due to the highnumber of individual frames used (193 in total). We have detected sixpeculiar objects in NGC 6705 and NGC 6756 from which one in the latteris almost certainly an unreddened late type foreground star. Theremaining five stars are probably cluster members and bona fidechemically peculiar objects (two are łambda Bootis typecandidates). Furthermore, we have investigated NGC 3114, a cluster forwhich already photoelectric Δ a-measurements exist. A comparisonof the CCD and photoelectric values shows very good agreement. Again,the high capability of our CCD Δ a-photometric system to sort outtrue peculiar objects together with additional measurements from broador intermediate band photometry is demonstrated.Based on observations obtained at Complejo Astronómico elLeoncito (CASLEO), operated under the agreement between the ConsejoNacional de Investigaciones Científicas y Técnicas de laRepública Argentina and the National Universities of La Plata,Córdoba y San Juan; ESO-La Silla, UTSO-Las Campanas and L. FiglObservatory, Mt. Schöpfl (Austria).Figure 1 and Table 2 are only available in electronic form athttp://www.edpsciences.org
| Theoretical isochrones for the Delta a photometric system
We have calculated theoretical isochrones for the photometric Delta asystem to derive astrophysical parameters such as the age, reddening anddistance modulus for open clusters. The Delta a system samples the fluxdepression at 520 nm which is highly efficient to detect chemicallypeculiar (CP) objects of the upper main sequence. The evolutionarystatus of CP stars is still a matter of debate and very important totest, for example, the dynamo and diffusion theories. In fact, thedynamo or fossil origin of the magnetic fields present in this kind ofstar is still not clear. Using the stellar evolutionary models by Claret(\cite{Cla95}), a grid of isochrones with different initial chemicalcompositions for the Delta a system was generated. The published dataof 23 open clusters were used to fit these isochrones with astrophysicalparameters (age, reddening and distance modulus) from the literature. Asan additional test, isochrones with the same parameters for Johnson UBVdata of these open clusters were also considered. The fits show a goodagreement between the observations and the theoretical grid. We findthat the accuracy of fitting isochrones to Delta a data without theknowledge of the cluster parameters is between 5 and 15%.
| On the Galactic Disk Metallicity Distribution from Open Clusters. I. New Catalogs and Abundance Gradient
We have compiled two new open cluster catalogs. In the first one, thereare 119 objects with ages, distances, and metallicities available, whilein the second one, 144 objects have both absolute proper motion andradial velocity data, of which 45 clusters also have metallicity dataavailable. Taking advantage of the large number of objects included inour sample, we present an iron radial gradient of about -0.063+/-0.008dex kpc-1 from the first sample, which is quite consistentwith the most recent determination of the oxygen gradient from nebulaeand young stars, about -0.07 dex kpc-1. By dividing clustersinto age groups, we show that the iron gradient was steeper in the past,which is consistent with the recent result from Galactic planetarynebulae data, and also consistent with inside-out galactic diskformation scenarios. Based on the cluster sample, we also discuss themetallicity distribution, cluster kinematics, and space distribution. Adisk age-metallicity relation could be implied by those properties,although we cannot give conclusive result from the age- metallicitydiagram based on the current sample. More observations are needed formetal-poor clusters. From the second catalog, we have calculated thevelocity components in cylindrical coordinates with respect to theGalactic standard of rest for 144 open clusters. The velocitydispersions of the older clusters are larger than those of youngclusters, but they are all much smaller than that of the Galactic thickdisk stars.
| Proper Motions of Open Star Clusters and the Rotation Rate of the Galaxy
The mean proper motions of 167 Galactic open clusters withradial-velocity measurements are computed from the data of the Tycho-2catalog using kinematic and photometric cluster membership criteria. Theresulting catalog is compared to the results of other studies. The newproper motions are used to infer the Galactic rotation rate at the solarcircle, which is found to be ω0=+24.6±0.8 km s-1 kpc-1.Analysis of the dependence of the dispersion of ω0 estimates onheliocentric velocity showed that even the proper motions of clusterswith distances r>3 kpc contain enough useful information to be usedin kinematic studies demonstrating that the determination of propermotions is quite justified even for very distant clusters.
| Morphological analysis of open clusters' propertiesII. Relationships projected onto the galactic plane
A morphological analysis study of open clusters' properties has beenachieved for a sample of 160 UBVCCD open star clusters of approximately128,000 stars near the galactic plane. The data was obtained and reducedfrom using the same reduction procedures, which makes this catalogue thelargest homogeneous source of open clusters' parameters.
| Integrated photometric characteristics of galactic open star clusters
Integrated UBVRI photometric parameters of 140 galactic open clustershave been computed. Integrated I(V-R)0 and I(V-I)0colours as well as integrated parameters for 71 star clusters have beenobtained for the first time. These, in combination with published data,altogether 352 objects, are used to study the integrated photometriccharacteristics of the galactic open clusters. The I(MV)values range from -9.0 to -1.0 mag corresponding to a range in totalmass of the star clusters from ~ 25 to 4*E4 Msun.The integrated colours have a relatively narrow range, e.g., I(B-V){_0}varies from -0.4 to 1.2 mag. The scatter in integrated colours at agiven integrated magnitude can be understood in terms of differences infraction of red giants/supergiants in the clusters. The observedintegrated magnitudes and colours agree with the synthetic ones, exceptthe dependences of I(V-R)0 and I(V-I)0 colours forclusters younger than ~ 100 Myrs and also of the integrated magnitudesof oldest clusters. The large sample provides the most accurate agedependence of integrated magnitudes and colours determined so far. Theluminosity function of the I(MV) has a peak around -3.5 magand its slope indicates that only ~ 1% of the open clusters in thegalactic disc are brighter than I(MV)=-11 mag. No variationhas been found of integrated magnitude with galactocentric distance andmetallicity.
| Abundance Gradient from Open Clusters and Implications for the Galactic Disk Evolution
We compile a new sample of 89 open clusters with ages, distances andmetallicities available. We derive a radial iron gradient of about-0.099±0.008 dexkpc (unweighted) for the whole sample, which issomewhat greater than the most recent determination of oxygen gradientfrom nebulae and young stars. By dividing the clusters into age groups,we show that the iron gradient was steeper in the past and has evolvedslowly in time. Current data show a substantial scatter of the clustermetallicities indicating that the Galactic disk has undergone a veryrapid, inhomogeneous enrichment.Also, based on a simple, but quitesuccessful model of chemical evolution of the Milky Way disk, we make adetailed calculation of the iron abundance gradient and its timeevolution. The predicted current iron gradient is about -0.072 dexkpc.The model also predicts a steady flattening of the iron gradient withtime, which agrees with the result from our open cluster sample.
| A study of spatial structure of galactic open star clusters
In order to study the relation between the core and corona in galacticstar clusters, the spatial structure of 38 rich open star clusters hasbeen studied using radial density profiles derived from the photometricdata of the Digital Sky Survey. The shape of the radial density profileindicates that the corona, most probably, is the outer region around thecluster. It can exist from the very beginning of the cluster formationand dynamical evolution is not the reason for its occurrence. The studydoes not find any relation between cluster size and age but indicatesthat the clusters with galacto-centric distances >9.5 kpc have largersizes. Further, we find that the average value of the core radius is1.3+/- 0.7 pc and that of annular width of the corona is 5.6+/- 1.9 pc,while average values of densities of cluster members in the core andcorona are 15.4+/- 9.9 star/pc2 and 1.6+/- 0.99star/pc2 respectively. Average field star contaminations inthe core and corona are ~ 35% and 80% respectively. In spite of smallerdensities in the coronal region, it contains ~ 75% of the clustermembers due to its larger area in comparison to the core region. Thisclearly demonstrates the importance of the coronal region in studiesdealing with the entire stellar contents of open star clusters as wellas their dynamical evolution. In contrast to the cluster cores, thestructure of coronal regions differs significantly from one cluster toother.
| Elemental Abundances in CP Stars of Galactic Open Clusters
Not Available
| Radial velocities, binarity, and kinematic membership in open clusters with blue straggler candidates
Not Available
| Star clusters in the Carina complex: UBVRI photometry of NGC 3114, Collinder 228 and vdB-Hagen 99
In this paper we present and analyze CCD UBVRI photometry in the regionof the three young open clusters NGC 3114, Collinder 228, and vdB-Hagen99, located in the Carina spiral feature. NGC 3114 lies in the outskirtsof the Carina nebula. We found 7 star members in a severely contaminatedfield, and obtain a distance of 950 pc and an age less than 3 x108 yrs. Collinder 228 is a younger cluster (8x106 yrs), located in front of the Carina nebula complex, forwhich we identify 11 new members and suggest that 30% of the stars areprobably binaries. As for vdB-Hagen 99, we add 4 new members, confirmingthat it is a nearby cluster located at 500 pc from the Sun and projectedtoward the direction of the Carina spiral arm. Based on observationstaken at ESO La Silla. Data are available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/136
| Proper motions of open clusters within 1 kpc based on the TYCHO2 Catalogue
We present mean absolute proper motions of 112 open clusters, determinedusing the data from the Tycho2 Catalogue. For 28 clusters, this is thefirst determination of proper motion. The measurements made use of alarge number of stars (usually several tens) for each cluster. The totalnumber of stars studied in the fields of the 164 open clusters is 5016,of which 4006 were considered members. The mean proper motions of theclusters and membership probability of individual stars were obtainedfrom the proper motion data by applying the statistical method proposedby Sanders (\cite{Sanders71}). Based on observations of the ESAHipparcos satellite. Tables 1, 2 and 5 to 117 are 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/376/441
| Morphological analysis of open clusters' propertiesI. Properties' estimations
A sample of 160 UBVCCD observations of open star clusters near thegalactic plane has been studied, and a catalogue of their propertiesobtained. The main photometrical properties have been re-estimated selfconsistently and the results have been compared with those of Lynga[Lynga, G., 1987. Catalog of Open Cluster Data, 5th Edition, StellarData Centers, Observatoire de Strasbourg, France].
| Hipparcos Trigonometric Parallaxes and the Distance Scale for Open Star Clusters
Hipparcos trigonometric parallaxes are used to estimate the distances tothe maximum possible number of open star clusters (OSC); distance moduliare estimated for 45 clusters with maximum heliocentric distances ofabout 1000 pc. The latter value can serve as an estimate of the limit towhich it still makes sense to use Hipparcos trigonometric parallaxes todetermine the distances to small groups composed of 6-10 sufficientlybright stars. A systematic correction to the distance moduli of clustersfrom the homogeneous catalog of OSC parameters (Loktin et al. 1997,2000) is estimated, which turns out to be independent of the clusterage.
| On the detection of the first extragalactic classical chemically peculiar stars
We report on the detection of the first extragalactic, classicalchemically peculiar (CP) stars more than 100 years after the discoveryof this group. Using the tool of CCD Delta a-photometry, eight definitepositive detections in the globular-like stellar cluster NGC 1866 andits surrounding in the Large Magellanic Cloud were made. More than 1950objects within a radius of 9.5arcmin of the cluster center down to 20.5magnitude were observed in this three filter, narrow band photometricsystem. Averaging more than 70 individual frames for all three filtersyielded a 3sigma detection limit of 0.015 mag for stars with V=20 mag.Furthermore we found three objects with significantly negative Deltaa-values indicating either an Ae/shell or lambda Bootis nature. Theoverall percentage of chemically peculiar stars for NGC 1866 (1.5%)seems lower than for the majority of open clusters in our Milky Waywhereas the incidence within the LMC field is decisively less (0.3%).Based on observations obtained at Complejo Astronómico elLeoncito (CASLEO), operated under the agreement between the ConsejoNacional de Investigaciones Científicas y Técnicas de laRepública Argentina and the National Universities of La Plata,Córdoba y San Juan.
| Radial Velocities and Kinematic Membership in the Open Cluster NGC 3114
Echelle spectroscopic observations for 30 bright stars in the field ofthe sparse open cluster NGC 3114 are presented. The sample includesmain-sequence stars, yellow and red giants, and blue stragglercandidates. Radial velocities are derived by cross-correlations usinghigh signal-to-noise ratio standard spectra as templates. The clustermean velocity is well defined from eight giants and severalmain-sequence stars whose average is =-3.52+/-0.25 kms-1. The membership probabilities of the observed stars arecomputed on the basis of the velocity distributions of the cluster andfield stars, and the expected percentage of contamination at eachposition. We classified 19 cluster members and 10 nonmembers; theremaining star is a known spectroscopic binary for which no membershipprobability was assigned. Among the members, there is a bright yellowgiant, seven red giants, and four blue straggler candidates, althoughthey should be considered as turn-off stars. The location of two of themin the color-magnitude diagram (slightly blueward of the turn-off) canbe explained by their low rotational velocities. No velocity variationswere detected in the 16 stars measured more than once, which indicatesthat NGC 3114 possess an abnormally low binary frequency. From spectraltypes of cluster members, a distance modulus (V-Mv)=9.8+/-0.2mag and a reddening E(B-V)=0.07+/-0.01 mag are derived. The cluster ageis estimated to be 1.6×108 yr. The observationspresented here were obtained at the Complejo Astronómico ElLeoncito (CASLEO), which is operated under agreement between the ConsejoNacional de Investigaciones Científicas y Técnicas de laRepública Argentina (CONICET) and the National Universities of LaPlata, Córdoba and San Juan.
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