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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}
| Spectroscopic and photometric observations of the short-period RS CVn-type star CG Cyg
Spectroscopic observations around the Halpha line and BVRphotometry of the eclipsing short-period RS CVn-star CG Cyg arepresented. The solutions of the radial velocity curves and the lightcurves yielded the following masses and radii of the star components:M1=0.97 Msun, M2=0.80 Msun,R1=1.00 Rsun, R2=0.83 Rsun.The measured rotational broadenings of the observed lines correspond toequatorial velocities V1=80 km s-1 andV2=66 km s-1. The distortions of our multicolorlight curve were reproduced by two cool spots on the primary star. Thestrong absorption feature between the spectral lines of the two starswas explained by extended structure around the mass center of thesystem. The Halpha emission line of the secondary star inthe August spectra was attributed to a prolonged flare of this star.Based on spectral observations at the 2-m Rozhen telescope, operated bythe National Astronomical Observatory; the research was supported inpart by grants of project No. 1/2002 of Shoumen University.
| New Variable Stars Discovered in the MISAO Project VII: MisV0351-MisV0400
This report describes 50 new variable stars (MisV0351-MisV0400)discovered in the course of the MISAO Project.
| The BVJK Lightcurves of the Shortperiod Eclipsing Binary Cg-Cygni
Abstract image available at:http://adsabs.harvard.edu/abs/1987A&A...182..264B
| CG Cygni - Solutions of 1979 and 1980 light curves
Three light curves of CG Cyg from 1979 and 1980 are presented, and thedata are examined using Fourier analysis. A time of minimum light iscomputed for each light curve; the light curves were rectified, and thecombined light curve is solved. The behavior of the Fourier coefficient,A(0), and the amplitude and position of the wave are studied.
| A New Light Curve of CG Cyg
Not Available
| BD +34 deg 4216 - A composite spectrum binary system
The star BD +34 deg 4216 has a composite spectrum. Spectroscopy,photometry, and spectrophotometry of this object show that it is aphysical binary consisting of an early-type dwarf and a late-type giant.The variable radial velocity of each component confirms this conclusion.
| Positions moyennes et mouvements propres de 355 etoiles DU GC de la zone de declinaison +33 +36.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...26..219M&db_key=AST
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Observation and Astrometry data
| Constellation: | Cygne |
| Right ascension: | 20h57m13.10s |
| Declination: | +35°18'42.2" |
| Apparent magnitude: | 6.616 |
| Distance: | 228.833 parsecs |
| Proper motion RA: | 5.5 |
| Proper motion Dec: | 7.9 |
| B-T magnitude: | 8.547 |
| V-T magnitude: | 6.776 |
Catalogs and designations:
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INHABITED SKY
