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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}
| Extent of Excess Far-Infrared Emission around Luminosity Class III Stars
With the Infrared Space Observatory, we conducted 3×3 pixelimaging photometry of 12 luminosity class III stars, which werepreviously presumed to have dust particles around them, at far-infraredwavelengths (60 and 90 μm). Eleven out of 12 targets show a peak ofexcess (above photosphere) far-infrared emission at the location of thestar, implying that the dust particles are truly associated with stars.To estimate the size of the excess emission source, the flux ratio ofcenter to boundary pixels of the 3×3 array was examined. Theradius of the dust emission is found to be ~3000 to ~10,000 AU for athin shell distribution and ~5000 to ~25,000 AU for a uniformdistribution. We consider three models for the origin of the dust:disintegration of comets, sporadic dust ejection from the star, andemission from nearby interstellar cirrus. The data seem to rule out thefirst model (as far as the ``Kuiper belt-like'' particles are assumed tobe large blackbody grains) but do not enable us to choose between theother two models.
| Late-type giants with infrared excess. I. Lithium abundances
de la Reza et al. (1997) suggested that all K giants become Li-rich fora short time. During this period the giants are associated with anexpanding thin circumstellar shell supposedly triggered by an abruptinternal mixing mechanism resulting in the surface Li enrichment. Inorder to test this hypothesis twenty nine late-type giants withfar-infrared excess from the list of Zuckerman et al. (1995) wereobserved in the Li-region to study the connection between thecircumstellar shells and Li abundance. Eight giants have been found tohave log epsilon (Li) > 1.0. In the remaining giants the Li abundanceis found to be much lower. HD 219025 is found to be a rapidly rotating(projected rotational velocity of 23 +/-3 km s(-1) ), dusty and Li-rich(log epsilon (Li) = 3.0+/-0.2) K giant. Absolute magnitude derived fromthe Hipparcos parallax reveals that it is a giant and not apre-main-sequence star. The evolutionary status of HD 219025 seems to besimilar to that of HDE 233517 which is also a rapidly rotating, dustyand Li-rich K giant. The Hipparcos parallaxes of all the well studiedLi-rich K giants show that most of them are brighter than the ``clump"giants. Their position in the H-R diagram indicates that they have gonethrough mixing and the initial abundance of Li is not preserved. Thereseems to be no correlations between Li abundances, rotational velocitiesand carbon isotope ratios. The only satisfactory explanation for theoverabundance of lithium in these giants is the creation of Li by theextra deep mixing and the associated ``cool bottom processing". Based onobservations obtained at the European Southern Observatory, La Silla,Chile, and at the Observatoire de Haute Provence, France.
| A Search for Lithium-Rich Giants among Stars with Infrared Excesses
The unusual nature of the single, rapidly rotating, lithium-rich K giantHDE 233517, which is currently undergoing significant mass loss,prompted a search for giants with similar properties. High-dispersionspectroscopic observations were obtained of HD 219025, a knownlithium-rich infrared-excess giant, plus 39 stars from a list of G and Kgiants with excess far-infrared emission. The projected rotationalvelocities of the vast majority of infrared-excess giants appear to besimilar to those of normal G and K giants. Six giants have lithiumabundances at or above theoretical upper envelope values. The percentageof such stars in the sample of 39 infrared-excess giants is similar tothat of normal giants. The three giants with the largest lithiumabundances have previously been discovered. None of the sample of 39giants have an Hα line similar to the broadened and veryasymmetric line of HDE 233517. The star with optical properties mostsimilar to HDE 233517 is HD 219025.
| On a Rapid Lithium Enrichment and Depletion of K Giant Stars
A model scenario has recently been introduced by de la Reza andcolleagues to explain the presence of very strong Li lines in thespectra of some low-mass K giant stars. In this scenario all ordinary,Li-poor, K giants become Li rich during a short time (~105 yr) whencompared to the red giant phase of 5 x 107 yr. In this "Li period," alarge number of the stars are associated with an expanding thincircumstellar shell supposedly triggered by an abrupt internal mixingmechanism resulting in a surface new 7Li enrichment. This Letterpresents nearly 40 Li-rich K giants known up to now. The distribution ofthese Li-rich giants, along with 41 other observed K giants that haveshells but are not Li rich, in a color-color IRAS diagram confirms thisscenario, which indicates, also as a new result, that a rapid Lidepletion takes place on a timescale of between ~103 and 105 yr. Thismodel explains the problem of the presence of K giants with far-infraredexcesses presented by Zuckerman and colleagues. Other present and futuretests of this scenario are briefly discussed.
| Giants with infrared excess.
We have correlated optical and infrared catalogs in order to extract alarge sample of luminosity class III stars with known infrared fluxdensities. For a non-negligible fraction of G and K giants, afar-infrared excess emission was found, starting beyond 25μm. Anexplanation in terms of present-day mass loss thus becomes unlikely,since the dust should then be warmer and the excess emission less far inthe infrared. We believe that the far-infrared excesses of theseobjects, most likely first-ascent giants, are related to the Vegaphenomenon. The dusty disks around these stars, gradually cooled downduring their main-sequence phase, could be reheated once the star leavesthe main sequence and enters the luminous post-main-sequence phase. Thefairly large sample we constructed enables us to derive an estimationfor the occurrence of excesses. This fraction of G or K giants withfar-infrared excess appears to be distinctly smaller than amongmain-sequence stars. Since the higher radiation field of giants couldlead to a larger evaporation rate of the circumstellar debris, this factdoes not conflict with our hypothesis.
| Luminosity Class III Stars with Excess Far-Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...446L..79Z&db_key=AST
| 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.
| The photometric variability of K giants
We have photometrically monitored 49 of the more than 200 K giants inthe Yale Catalog of Bright Stars (YCBS) which are named or suspectedvariable stars. Only two (HR 3275 and HR 5219) are clearly variable; afew more program stars and K- and M-giant comparison stars aremarginally variable. Most of these appear to be RS Canum Venaticorum orSR variables.
| MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington
MK spectral classifications are given for 591 stars which are used fortime and latitude observations at Mizusawa and Washington. Theclassifications in the MK system were made by slit spectrograms ofdispersion 73 A/mm at H-gamma which were taken with the 91 cm reflectorat the Okayama Astrophysical Observatory. Photometric observations in UBV were made with the 1-meter reflector at the Flagstaff Station of U.S.Naval Observatory. The spectrum of HD 139216 was found to show a strongabsorption line of H-beta. The following new Am stars were found:HD9550, 25271, 32784, 57245, 71494, and 219109. The following new Apstars were found: HD6116, 143806, 166894, 185171, and 209260. The threestars, HD80492, 116204, and 211376, were found to show the emission inCaII H and K lines.
| Narrow-band photometry of late-type stars. II
This paper presents extensive narrow-band photometry in the Uppsalasystem supplementing earlier published mesurements so that data now areavailable for all late-type stars brighter than V = 6.05 and a number ofgalactic cluster members. Numerous UBV and BV measurements are alsopublished. The data are used to determine relations for the predictionof UBV intrinsic colors for late-type stars from the narrow-bandmeasurements. The main purpose of the data is to constitute the basisfor the determination of solar-neighborhood space densities of late-typestars, mainly giants of different kinds; these space densities will becombined with narrow-band data for fainter stars in the north Galacticpole region to yield the decrease of space density with distance fromthe galactic plane for many kinds of late-type stars.
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
| Visual multiples. VIII - 1000 MK types
A total of 1000 new classifications are given for stars brighter than B= 8.0 mag in the Aitken double star catalog. The classificationssupplement 865 classifications obtained in 1981 and 1984. Among thenewly discovered stars are 12 new Ap stars, eight Lambda Bootis stars,one Ba II star, and 60 Am stars. A detailed list of the newclassifications is given.
| Photoelectric UBV photometry for 317 PZT and VZT stars
UBV data were taken of 317 stars to fill gaps in photoelectric recordsneeded for establishing a terrestrial reference frame for earthorientation purposes. The study supplied the magnitudes and colors andaided in identifying nearby stars without trigonometric parallaxes. Thesurvey averaged over three observations of each object. A complete tableof the V, B-V, U-B and number of observations of each object isprovided.
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| Takýmyýldýz: | Zincirli Prenses |
| Sað Açýklýk: | 23h34m46.70s |
| Yükselim: | +38°01'26.0" |
| Görünürdeki Parlaklýk: | 6.18 |
| Uzaklýk: | 207.9 parsek |
| özdevim Sað Açýklýk: | 10.9 |
| özdevim Yükselim: | 11.1 |
| B-T magnitude: | 8.283 |
| V-T magnitude: | 6.367 |
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