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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
| Spectral Classification of "Photometric Subgiants" in Open Clusters
Color-magnitude diagrams of several intermediate-age open clusterscontain apparent post-main-sequence stars which are fainter thanpredicted by standard evolutionary tracks. We have obtainedclassification spectra for such stars in eight clusters. Some of theseare reddened background early-type stars, and several of the late-typestars turn out to have luminosities indicative of being foreground tothe cluster. A few stars appear to be cluster members but do not fit thetheoretical tracks. We find that the Bahcall-Soneira Galaxy model,modified for low galactic latitudes, can give statistically usefulpredictions of the numbers of field stars.
| Photometry of F-K type bright giants and supergiants. 3: The luminosity, reddening, and heavy element abundance of GK stars
The reddening, luminosity, and heavy element abundance of 250 brightgiants and supergiants of type GK are discussed on the basis of 4 color,DDO, RI, and Geneva photometry Bright giants of type GK with age greaterthan 5 x 108 yr, and of type G0/3 with age greater than 2 x108 yr, are very scarce in the solar neighborhood. The medianspace motion vectors of the bright giants and supergiants with welldetermined space motions are (U, V, W) = (+10.6, -13.2, -7.7) +/- (12.3,8.8, 8.8) km/s. The M1 index for 4 color photometry, whencorrected for luminosity (gravity) effects, is sensitive to heavyelement abundance of the GK stars but may not be reliable for those oftype G0/3. The available spectroscopic determinations of (Fe/H) givemixed results with the two largest samples being internally consistentbut with a large zero-point difference. There is a similar zero-pointshift in the peak frequency of the photometrically determined values ofP(Fe/H) for the F type and for the GK type stars. There is littleevidence for an appreciable galactic, radial gradient in the P(Fe/H)values. A previously noted correlation of the heavy element abundanceindex, delta M1, with the amplitude defect in the B lightcurves of Cepheids, FB, and interpretation of the(PLFB) relation as a (PL(Fe/H)) relation needs furtherinvestigation in light of the apparent sensitivity of M1 toFe/H for the F stars (the domain of the Cepheids with P less than 10 d)and lack of this sensitivity for the G0/3 star (domain of the Cepheidswith P greater than 10 d).
| Evolved GK stars near the Sun. 2: The young disk population
From a sample of nearly 2000 GK giants a group of young disk stars withwell determined space motions has been selected. The zero point of theluminosity calibrations, both from the ultraviolet flux (modifiedStroemgren system) and that in the region of 4200 to 4900 A (DDOsystem), show a discontinuity of about a half magnitude at the border ofthe young disk and old disk domains. The population separation is basedon the space velocity components, which are also an age discriminant,with the population interface near 2 x 109 yr, based onmodels with convective overshoot at the core. This age corresponds togiant masses near 1.7 solar mass, near the critical mass separating theyoung stars that do not burn helium in degenerate cores from older starsthat do. Ten percent of both populations show CN anomalies in that thederived value of P(Fe/H) from CN (Cm) and fromFe(M1) differ by more than 0.1 dex and the weak and strong CNstars occur equally in the old disk but the weak CN stars predominate inthe young disk. Peculiar stars, where flux distortions affect theluminosity calibrations, are of the CH+(Ba II) and CH-(weak G band)variety and represent less than 1% of the stars in both populations. Theyoung disk giants are restricted to ages greater than about109 yr, because younger stars are bright giants orsupergiants (luminosity class 2 or 1), and younger than about 2 x109 yr, because the old disk-young disk boundary occurs near1.7 solar mass. The distribution of heavy element abundances, P(Fe/H),for young disk giants is both more limited in range (+/- 0.4 dex) and isskewed toward higher abundances, compared with the nearly normaldistribution for old disk giants. The distribution of (U,V) velocityvectors gives (U,V,W) and their dispersions = (+17.6 +/- 18.4, -14.8 +/-8.4, -6.9 +/- 13.0) and (+3.6 +/- 38.4, -20.7 +/- 27.5, -6.7 +/-17.3)km/s for young and old disk giants, respectively.
| NGC 2287 - an important intermediate-age open cluster
We have obtained photoelectric UBV photometry for 100 stars, uvby-betaphotometry for 39 stars, and MK spectral types for 80 stars in the fieldof NGC 2287. After combination with data from other sources, severalinteresting cluster properties are apparent. Both the UBV and uvby-betaphotometry point to a small but nonzero reddening, while our spectraltypes confirm previous results indicating a high binary frequency forthe cluster. Based on our spectral and photometric data for the clustermembers with M(V) of between -1 and 3, we find a minimum binaryfrequency of 40 percent and discuss the possibility that the results mayimply a binary frequency closer to 80 percent. The cluster age is foundto be about 2 x 10 exp 8 yr based on both the main-sequence turnoff andthe red giant distribution; the width of the turnup region can probablybe explained by a combination of duplicity and a range in stellarrotation.
| Photometry of F-K type bright giants and supergiants. I - Intermediate band and H-Beta observations
Over 1500 observations of 560 bright giants and supergiants of types F-Kare presented and compared to the observations by Gray and Olsen (1991).The present results include intermediate-band which is slightlydifferent from the Stromgren data by Gray and Olsen due to a differentwidth for the v filter. A systematic difference in m(1) - M(1) withdecreasing temperature is noted in the two H-Beta data sets, and thecorrelations are defined.
| More radial-velocity measurements in young open clusters
Further high resolution radial-velocity measurements are reported in 23young open clusters using the Kitt Peak CCD coude spectrograph on the0.9-m feed telescope. The radial velocities for the cluster stars arederived with the technique of cross correlation. The internal precisionof the velocity measurements is typically 2 km/s for early type stars.From these new data and previously published velocities, the observedstars in two clusters, NGC 663 and NGC 2287, were found to show arelatively small dispersion in the measured mean velocities. Furtherobservations of stars in young clusters will be useful in helping toestablish an early-type-star-velocity standard system.
| First giant branch and asymptotic giant branch stars in nearby aggregates
The properties of the brightest red stars in several aggregates in theGalaxy are compared with theoretical models. 22 asymptotic giant branch(AGB) stars are identified, four of which are in the thermally pulsingAGB (TPAGB) phase and four of which are TPAGB carbon stars. Also, fourcases of RGB stars are identified which have accreted substantial massfrom the carbon-rich TPAGB precursor of a current white dwarf companion.There is general agreement between the observed and theoretical slopesof the RGB and early AGB branches, and quantitative differences betweenthe positioning of observed sequences can be understood in terms ofdifferences in metallicity and mass predicted by the theory.
| Radial velocities of stars in open clusters
A CORAVEL type spectrometer was used to measure precise radialvelocities of 116 late-type stars of spectral classes F5 - M5 in thefields of 18 open clusters. Probable cluster members were selected onthe basis of kinematic and photometric data. New or improved radialvelocities for 12 open clusters were thus obtained.
| Colour excesses and absolute magnitudes for non-Cepheid F-G supergiants from uvbybeta photometry
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&A...239..205A&db_key=AST
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| 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.
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| Radial-velocity measurements in 20 young open clusters
The further results of a program to determine the radial velocities ofyoung open clusters are presented. Using the KPNO coude spectrographcoupled with the 1-m feed and 2.1-m telescopes, radial velocities havebeen measured for nearly one hundred stars, most of which are ofspectral type B and A, in 20 young clusters. The combination ofinstruments and the use of cross-correlation techniques show that radialvelocities of B and A type stars as faint as 10th magnitude can bedetermined with an internal precision of less than about 2 km/s. Asexpected, the uncertainties in the velocity determination for the youngclusters are dominated by spectroscopic binary stars in these clusters.A third of the stars in the sample are found to be spectroscopicbinaries, but with a large variation in the frequency of binaries fromcluster to cluster. Because the time coverage is still limited, thisshould be considered a lower limit to the binary frequency. Clustervelocities are determined after eliminating binaries and known nonmemberstars. The new velocities are compared with a model galactic rotationcurve, as well as with previous velocity determinations.
| Radial velocities in the direction of the cluster NGC 2287
Mean radial velocities for 72 stars in the direction of NGC 2287 havebeen determined based on 10 plates obtained with the 40-cm ObjectivePrism of the La Silla ESO. The radial velocities are given in the IAUsystem with an accuracy of + or - 5 km/s. It is found that the peculiarstar HD 49022 is variable and has an amplitude of 70 km/s. The generalvelocity diagram has a maximum at about 22 km/s which may represent amixture of cluster and field stars and an asymmetry at 30 km/s which maybe attributed to binary member stars.
| Age determination of the open cluster NGC 2287 (M41)
Two different methods which take into account the rotation of the memberstars are used to determine the cluster age of NGC 2287 (M41). Thetheoretical Hertzsprung-Russell diagram is first obtained from theobserved color-magnitude diagram. The method based on the turn-off pointon the cluster Main Sequence yields an age of 3.10 x 10 to the 7th yr.By fitting the evolutionary tracks of rotating stars to the clusterHertzsprung-Russell diagram, an age of about 8.00 x 10 to the 7th yr isobtained.
| 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.
| On the Constancy of Some Stars in NGC 2287 = Messier 41
Not Available
| Membership in the open cluster NGC 2287
The open cluster NGC 2287 is a cluster apparently rich in multiple starsand several other spectroscopically interesting objects. The firstextended proper-motion membership survey of the cluster is reported. UBVphotometry of 146 proper-motion stars is also included and compared toearlier data. Color-magnitude and two-color diagrams are presented. Theproper-motion-based membership probabilities indicate that most of thespectroscopic binaries are members of the cluster, as are the threeHg-Mn stars, and at least four of the K giants. The bright He-weak starHD 49333 does not appear to be a cluster member. A ZAMS fit to acolor-magnitude diagram of the most likely members gives a distancemodulus of (m - M) = 9.15.
| Galactic cluster star radial velocities obtained with a focal reducer field spectrograph. I - The clusters IC 1805, NGC 2287, NGC 2548, IC 4665, NGC 6633, NGC 6940 and NGC 7092
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...62..301G&db_key=AST
| DDO photometry on red giants in the open clusters NGC 2232, NGC 2287, and NGC 2451
From DDO photometry combined with U, B, V photometry of red stars in theopen clusters NGC 2232, NGC 2287, and NGC 2451, the mean color excess E(B-V), the distance modulus, and the mean metal abundance (Fe/H) werederived for the clusters. The physical parameters, surface gravity,effective temperature, and spectral type were also obtained for the redstars. Estimation of age yielded 1.1 x 10 to the 8th yr for NGC 2287,and for NGC 2451, 4.8 x 10 to the 8th. The cluster NGC 2232 should beolder than 10 to the 9th yr.
| Positions of stars in regions of 14 southern galactic clusters
Positions have been obtained for a total of 3487 stars scattered over 14regions that are centered on each of the southern galactic clusters NGC1981, 2287, 2437, 2451, 2516, 2546, 2547, 2548, 3114, 3532, IC 2391,2395, 2602, and Truempler 10. A frame of reference has been establishedfor each region using ESO Schmidt plates centered on the clusters, witheach plate containing 20-35 measurable Perth 70 stars that are used fordetermining the positions of 200-400 fainter stars within a centralfield of 25 min of arc radius (covering the corresponding 1.5-m plates).
| The region of NGC 2287 and CR 121
Intermediate band and H-beta observations of 135 stars in the regions ofthe clusters NGC 2287 and Cr 121 are discussed, and a luminositycalibration of photometric parameters for late G- to early K-type brightgiants and supergiants is introduced. Results indicate that NGC 2287 isat a distance of 740 pc, very little reddened, 100-million years old,and contains three or four G8-K2 bright giants and supergiants and ablue straggler. Cr 121 is 1.17 kpc distant, very little reddened, 1.5million years old and an extension of CMa OB1. Cr 121 contains a nearerconcentration of stars at the same distance as NGC 2287, and theassociation appears to be the same age as CMa OB1, although presequencestars may exist. Intermingling of stars in CMa OB2 and NGC 2287 is alsoconsidered possible, and a test of the calibration of two methods ofluminosity determination of early A-type stars using photometricparameters shows them to be entirely consistent.
| Spectral morphology in the open cluster NGC 2287
Spectral classifications in NGC 2287 have revealed the presence of anHe-weak star, three Hg-Mn stars, one star with a weak K line, one coolAp star and one star with a composite spectrum. Spectroscopic evidencedetermined eight double-line binaries as well as five suspecteddouble-line binaries.
| Mulitcolor Photometry of the Open Cluster NGC 2287
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...34..241F&db_key=AST
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