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Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only 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/430/165}
| 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
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Study of proper motions in the region of the open cluster M67 and membership of stars
Relative proper motions and membership probabilities of 1046 stars inthe open cluster M67 area are determined from PDS measurements of nineplate pairs taken with the double astrograph at the Zo-Se station ofShanghai Observatory, which has an aperture of 40 cm, a focal length of6.9 m and a scale of 30 arcsec/mm. The number of stars with membershipprobabilities higher than 0.8 and at a distance less than 45 arcmin fromthe field center is 282. The average standard errors of proper motionsvary from +/- 0.0004 arcsec/yr for bright stars in the inner part of thefield to some +/- 0.00l5 arcsec/yr for faint stars in the outer part ofthe cluster. It is shown by a detailed discussion that the propermotions and membership probabilities of the stars determined in thispaper are in quite satisfactory agreement with those obtained by Sanders(1977) or Girard et al. (1989).
| Cousins VRI standard stars in the M 67 dipper asterism
Cousins VRI data for 19 standard stars in the M 67 dipper asterism arepresented. With one exception, the values of sigma per mean for thesedata are lsss than 10 mmag. Because these stars are close together inthe sky, they can be used with economy of effort in standardizing CCDimages. New Cousins VRI photometry is reported for 23 M 67 stars. For 22additional cluster stars, new V magnitudes are reported. It is foundthat some published V data for the Hyades and M 67 must be corrected bysmall amounts to recover the Landolt (1983) zero point. In addition,faint-star M 67 measurements by Eggen and Sandage (1964) display scatterwhich is not easily interpreted. The same is true for the (largely)bright-star M 67 data of Johnson and Sandage (1955). The photomultipliercolors of Janes and Smith (1984) and the CCD data of Schild (1983, 1985)are also considered.
| Precise radial velocities of late-type stars in the open clusters M11 and M67
Precise radial-velocity measurements of 39 stars and 170 stars areobtained in the fields of the open clusters M11 and M67, respectively;by the vast majority of the stars observed are cluster members. Allstars observed are of spectral type later than F5; the data set includesessentially all of the giants in both clusters and all main-sequencestars in M67 brighter than V = 12.8, plus an assortment of nonmembersand fainter members. Single-measurement precisions range from 0.3 to 0.8km/s. Almost all stars have been observed repeatedly, with clustermembers typically having 5-25 velocity measurements. Observations wereobtained over a span of 16 yr, although not all stars were observedthroughout that period. The time distribution of the observations is acombination of low-frequency coverage (less than 1/yr) over the first 11yr, and higher-frequency coverage (greater than 2/yr) over the final 5yr.
| Cousins VRI photometry of the Hyades, Coma, and M67
For little-evolved stars in the Hyades, Coma, and M67, Cousins VRIphotometry which includes and expands on results published in othersystems by Taylor is presented. Observing and reduction procedures anderror analysis are discussed in some detail, and evidence is presentedthat the transformations to the Cousins system are satisfactory and theresults are internally consistent. Comparisons with data published byMendoza yield agreement in R-I and V-R for the Hyades and V-R for M67.Disagreement is found, however, in both color indices for Coma and inR-I for M67, and reasons are suggested for favoring the obtained resultsin these cases. By comparing Mendoza's M67 K-giant data with those ofother observers, it is found that any problem with Mendoza's M67 resultsis apparently limited to the faintest stars he observed. A suggestion bySchild and Weeks that Mendoza's M67 R magnitudes are about 0.1 mag inerror is also tested, and it is found that available evidence does notsupport this suggestion.
| Photoelectric measurements of lunar occultations. VIII
Photoelectric timings are reported for 276 lunar occultation eventswhich were observed between March 1975 and February 1976. The timings(in UTC) are based on Loran G equipment of a lunar laser-ranging groupor on WWV signals. Angular diameters are determined for HR 5301, HD176124, Chi-1-Orionis, and HR 601. Twenty cases of possible or actualdouble stars, including Beta Capricorni, are noted along with oneprobable triple system (51 Piscium). Several technical and computationaldifficulties encountered in this program are discussed.
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
| Investigation of proper motions in the field of the cluster M 67 II,
Not Available
| Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
| New photoelectric observations of stars in the old galactic cluster M67
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...140..130E&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Rák |
| Rektaszcenzió: | 08h51m49.36s |
| Deklináció: | +11°53'39.0" |
| Vizuális fényesség: | 7.859 |
| Távolság: | 226.244 parszek |
| RA sajátmozgás: | -11.3 |
| Dec sajátmozgás: | 3.8 |
| B-T magnitude: | 9.285 |
| V-T magnitude: | 7.977 |
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