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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}
| Carbon-rich giants in the HR diagram and their luminosity function
The luminosity function (LF) of nearly 300 Galactic carbon giants isderived. Adding BaII giants and various related objects, about 370objects are located in the RGB and AGB portions of the theoretical HRdiagram. As intermediate steps, (1) bolometric corrections arecalibrated against selected intrinsic color indices; (2) the diagram ofphotometric coefficients 1/2 vs. astrometric trueparallaxes varpi are interpreted in terms of ranges of photosphericradii for every photometric group; (3) coefficients CR andCL for bias-free evaluation of mean photospheric radii andmean luminosities are computed. The LF of Galactic carbon giantsexhibits two maxima corresponding to the HC-stars of the thick disk andto the CV-stars of the old thin disk respectively. It is discussed andcompared to those of carbon stars in the Magellanic Clouds and Galacticbulge. The HC-part is similar to the LF of the Galactic bulge,reinforcing the idea that the Bulge and the thick disk are part of thesame dynamical component. The CV-part looks similar to the LF of theLarge Magellanic Cloud (LMC), but the former is wider due to thesubstantial errors on HIPPARCOS parallaxes. The obtained meanluminosities increase with increasing radii and decreasing effectivetemperatures, along the HC-CV sequence of photometric groups, except forHC0, the earliest one. This trend illustrates the RGB- and AGB-tracks oflow- and intermediate-mass stars for a range in metallicities. From acomparison with theoretical tracks in the HR diagram, the initial massesMi range from about 0.8 to 4.0 Msun for carbongiants, with possibly larger masses for a few extreme objects. A largerange of metallicities is likely, from metal-poor HC-stars classified asCH stars on the grounds of their spectra (a spheroidal component), tonear-solar compositions of many CV-stars. Technetium-rich carbon giantsare brighter than the lower limit Mbol =~ -3.6+/- 0.4 andcentered at =~-4.7+0.6-0.9 at about =~(2935+/-200) K or CV3-CV4 in our classification. Much like the resultsof Van Eck et al. (\cite{vaneck98}) for S stars, this confirms theTDU-model of those TP-AGB stars. This is not the case of the HC-stars inthe thick disk, with >~ 3400 K and>~ -3.4. The faint HC1 and HC2-stars( =~ -1.1+0.7-1.0) arefound slightly brighter than the BaII giants ( =~-0.3+/-1.3) on average. Most RCB variables and HdC stars range fromMbol =~ -1 to -4 against -0.2 to -2.4 for those of the threepopulation II Cepheids in the sample. The former stars show the largestluminosities ( <~ -4 at the highest effectivetemperatures (6500-7500 K), close to the Mbol =~ -5 value forthe hot LMC RCB-stars (W Men and HV 5637). A full discussion of theresults is postponed to a companion paper on pulsation modes andpulsation masses of carbon-rich long period variables (LPVs; Paper IV,present issue). This research has made use of the Simbad databaseoperated at CDS, Strasbourg, France. Partially based on data from theESA HIPPARCOS astrometry satellite. Table 2 is 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/390/967
| Re-processing the Hipparcos Transit Data and Intermediate Astrometric Data of spectroscopic binaries. I. Ba, CH and Tc-poor S stars
Only 235 entries were processed as astrometric binaries with orbits inthe Hipparcos and Tycho Catalogue (\cite{Hipparcos}). However, theIntermediate Astrometric Data (IAD) and Transit Data (TD) made availableby ESA make it possible to re-process the stars that turned out to bespectroscopic binaries after the completion of the Catalogue. This paperillustrates how TD and IAD may be used in conjunction with the orbitalparameters of spectroscopic binaries to derive astrometric parameters.The five astrometric and four orbital parameters (not already known fromthe spectroscopic orbit) are derived by minimizing an objective function(chi 2) with an algorithm of global optimization. This codehas been applied to 81 systems for which spectroscopic orbits becameavailable recently and that belong to various families ofchemically-peculiar red giants (namely, dwarf barium stars, strong andmild barium stars, CH stars, and Tc-poor S stars). Among these 81systems, 23 yield reliable astrometric orbits. These 23 systems make itpossible to evaluate on real data the so-called ``cosmic error''described by Wielen et al. (1997), namely the fact that an unrecognizedorbital motion introduces a systematic error on the proper motion.Comparison of the proper motion from the Hipparcos catalogue with thatre-derived in the present work indicates that the former are indeed faroff the present value for binaries with periods in the range 3 to ~ 8years. Hipparcos parallaxes of unrecognized spectroscopic binaries turnout to be reliable, except for systems with periods close to 1 year, asexpected. Finally, we show that, even when a complete orbital revolutionwas observed by Hipparcos, the inclination is unfortunately seldomprecise. Based on observations from the Hipparcos astrometric satelliteoperated by the European Space Agency (ESA 1997).
| New CORAVEL spectroscopic-binary orbits of giant barium stars. II
This paper complements the set of spectroscopic orbits for giant bariumstars given in \cite[Udry et al. (1998)]{udry98} and provides data for20 binaries (18 orbits + 2 minimum-period determinations). Based onobservations obtained at the Haute-Provence Observatory (France) and atthe European Southern Observatory (ESO, La Silla, Chile).
| A CORAVEL radial-velocity monitoring of giant BA and S stars: Spectroscopic orbits and intrinsic variations. I.
With the aim of deriving the binary frequency among Ba and S stars, 56new spectroscopic orbits (46 and 10, respectively) have been derived forthese chemically-peculiar red giants monitored with the \coravel\spectrometers. These orbits are presented in this paper (38 orbits) andin a companion paper \cite[(Udry et al. 1998,]{Udry} Paper II; 18orbits). The results for 12 additional long-period binary stars (6 and6, respectively), for which only minimum periods (generally exceeding 10y) can be derived, are also presented here (10) and in Paper II (2). Theglobal analysis of this material, with a few supplementary orbits fromthe literature, is presented in \cite[Jorissen et al.(1998).]{Jorissen98} For the subsample of Mira S, SC and (Tc-poor) Cstars showing intrinsic radial-velocity variations due to atmosphericphenomena, orbital solutions (when available) have been retained if thevelocity and photometric periods are different (3 stars). However, it isemphasized that these orbit determinations are still tentative. Threestars have been found with radial-velocity variations synchronous withthe light variations. Pseudo-orbital solutions have been derived forthose stars. In the case of RZ Peg, a line-doubling phenomenon isobserved near maximum light, and probably reflects the shock wavepropagating through the photosphere. Based on observations obtained atthe Haute-Provence Observatory (France) and at the European SouthernObservatory (ESO, La Silla, Chile).
| Insights into the formation of barium and Tc-poor S stars from an extended sample of orbital elements
The set of orbital elements available for chemically-peculiar red giant(PRG) stars has been considerably enlarged thanks to a decade-longCORAVEL radial-velocity monitoring of about 70 barium stars and 50 Sstars. When account is made for the detection biases, the observedbinary frequency among strong barium stars, mild barium stars andTc-poor S stars (respectively 35/37, 34/40 and 24/28) is compatible withthe hypothesis that they are all members of binary systems. Thesimilarity between the orbital-period, eccentricity and mass-functiondistributions of Tc-poor S stars and barium stars confirms that Tc-poorS stars are the cooler analogs of barium stars. A comparative analysisof the orbital elements of the various families of PRG stars, and of asample of chemically-normal, binary giants in open clusters, revealsseveral interesting features. The eccentricity - period diagram of PRGstars clearly bears the signature of dissipative processes associatedwith mass transfer, since the maximum eccentricity observed at a givenorbital period is much smaller than in the comparison sample of normalgiants. be held The mass function distribution is compatible with theunseen companion being a white dwarf (WD). This lends support to thescenario of formation of the PRG star by accretion of heavy-element-richmatter transferred from the former asymptotic giant branch progenitor ofthe current WD. Assuming that the WD companion has a mass in the range0.60+/-0.04 Msb ȯ, the masses of mild and strong barium starsamount to 1.9+/-0.2 and 1.5+/-0.2 Msb ȯ, respectively. Mild bariumstars are not restricted to long-period systems, contrarily to what isexpected if the smaller accretion efficiency in wider systems were thedominant factor controlling the pollution level of the PRG star. Theseresults suggest that the difference between mild and strong barium starsis mainly one of galactic population rather than of orbital separation,in agreement with their respective kinematical properties. There areindications that metallicity may be the parameter blurring the period -Ba-anomaly correlation: at a given orbital period, increasing levels ofheavy-element overabundances are found in mild barium stars, strongbarium stars, and Pop.II CH stars, corresponding to a sequence ofincreasingly older, i.e., more metal-deficient, populations. PRG starsthus seem to be produced more efficiently in low-metallicitypopulations. Conversely, normal giants in barium-like binary systems mayexist in more metal-rich populations. HD 160538 (DR Dra) may be such anexample, and its very existence indicates at least that binarity is nota sufficient condition to produce a PRG star. This paper is dedicated tothe memory of Antoine Duquennoy, who contributed many among theobservations used in this study
| Barium stars, galactic populations and evolution.
In this paper HIPPARCOS astrometric and kinematical data together withradial velocities from other sources are used to calibrate bothluminosity and kinematics parameters of Ba stars and to classify them.We confirm the results of our previous paper (where we used data fromthe HIPPARCOS Input Catalogue), and show that Ba stars are aninhomogeneous group. Five distinct classes have been found i.e. somehalo stars and four groups belonging to disk population: roughlysuper-giants, two groups of giants (one on the giant branch, the otherat the clump location) and dwarfs, with a few subgiants mixed with them.The confirmed or suspected duplicity, the variability and the range ofknown orbital periods found in each group give coherent resultssupporting the scenario for Ba stars that are not too highly massivebinary stars in any evolutionary stages but that all were previouslyenriched with Ba from a more evolved companion. The presence in thesample of a certain number of ``false'' Ba stars is confirmed. Theestimates of age and mass are compatible with models for stars with astrong Ba anomaly. The mild Ba stars with an estimated mass higher than3Msun_ may be either stars Ba enriched by themselves or``true'' Ba stars, which imposes new constraints on models.
| Library of high and mid-resolution spectra in the CA II H & K, Hα, Hβ NA i D1, D2, and He i D3 line regions of F, G, K and M field stars
In this work we present spectroscopic observations centered in thespectral lines most widely used as optical indicators of chromosphericactivity (Hα, Hβ, Ca ii H & K, and He i D3) ina sample of F, G, K and M chromospherically inactive stars. The spectrahave been obtained with the aim of providing a library of high andmid-resolution spectra to be used in the application of the spectralsubtraction technique to obtain the active-chromosphere contribution tothese lines in chromospherically active single and binary stars. Thislibrary can also be used for spectral classification purposes. A digitalversion with all the spectra is available via ftp and the World Wide Web(WWW) in both ASCII and FITS formats. Based on observations made withthe Isaac Newton telescope and the William Herschel Telescope operatedon the island of La Palma by the Royal Greenwich Observatory at theSpanish Observatorio del Roque de Los Muchachos of the Instituto deAstrofisica de Canarias, and with the 2.2 m telescope of the CentroAstronomico Hispano-Aleman of Calar Alto (Almeria, Spain) operatedjointly by the Max Planck Institut fur Astronomie (Heidelberg) and theSpanish Comision Nacional de Astronomia. The spectra of the stars listedin Table \protect\ref{tab:par} are also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Absolute magnitudes and kinematics of barium stars.
The absolute magnitude of barium stars has been obtained fromkinematical data using a new algorithm based on the maximum-likelihoodprinciple. The method allows to separate a sample into groupscharacterized by different mean absolute magnitudes, kinematics andz-scale heights. It also takes into account, simultaneously, thecensorship in the sample and the errors on the observables. The methodhas been applied to a sample of 318 barium stars. Four groups have beendetected. Three of them show a kinematical behaviour corresponding todisk population stars. The fourth group contains stars with halokinematics. The luminosities of the disk population groups spread alarge range. The intrinsically brightest one (M_v_=-1.5mag,σ_M_=0.5mag) seems to be an inhomogeneous group containing bariumbinaries as well as AGB single stars. The most numerous group (about 150stars) has a mean absolute magnitude corresponding to stars in the redgiant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group containsbarium dwarfs, the obtained mean absolute magnitude is characteristic ofstars on the main sequence or on the subgiant branch (M_v_=3.3mag,σ_M_=0.5mag). The obtained mean luminosities as well as thekinematical results are compatible with an evolutionary link betweenbarium dwarfs and classical barium giants. The highly luminous group isnot linked with these last two groups. More high-resolutionspectroscopic data will be necessary in order to better discriminatebetween barium and non-barium stars.
| Excess Hα emission in chromospherically active binaries.
We study the behaviour of the excess Hα emission in a sample of 51chromospherically active binary systems (RS CVn and BY Dra classes), ofdifferent activity levels. This sample include the 27 stars analysed byFernandez-Figueroa et al. (1994) and the new observations of 24 systemsdescribed by Montes et al. (1994b). By using the spectral subtractiontechnique (subtraction of a synthesized stellar spectrum constructedfrom reference stars of similar spectral type and luminosity class) weobtain the active-chromosphere contribution to the Hα line inthese 51 systems. We have determined the excess Hα emissionequivalent widths and converted it to surface fluxes. The Hαemissions arising from each component star were obtained when it waspossible to deblend both contributions. The comparison of the excessHα emission, obtained with the spectral subtraction technique,with other Hα activity indices allows us to conclude that this isthe preferable activity indicator for binaries. The behaviour of theexcess Hα emission as a function of the rotation has beenanalyzed. A slight decline toward longer rotational periods, P_rot_, andlarger Rossby numbers, R_0_, is present in agreement with previousresults using others activity indicators. We have compared the derivedexcess Hα emission fluxes with those obtained in the Ca II K andHɛ lines finding that a good correlation exits between thesethree chromospheric activity indicators. The Hα losses seem to bemore important than Ca II K losses for cooler stars, in fact all thesystem with Hα emission above the continuum are cooler than 5000K.Correlations with other activity indicators, (C IV in the transitionregion, and X-rays in the corona) indicate that the exponents of thepower-law relations increase with the formation temperature of thespectral features.
| Excess Hα emission in chromospherically active binaries: the spectroscopic survey.
We present new spectroscopic Hα observations for a sample of 24chromospherically active binary systems (RS CVn and BY Dra classes), ofdifferent activity levels. By using the spectral subtraction technique(subtraction of a synthesized stellar spectrum constructed fromreference stars of similar spectral type and luminosity class) we obtainthe active-chromosphere contribution to the Hα line. The Hαemissions arising from each individual star were obtained when it waspossible to deblend the contribution of both components.
| The Wilson-Bappu effect and other CA II H and K line parameters relationships in chromospherically active binaries
We present measurements of the emission core width W_0_ and thewavelength separation of the K_1_ dips, W_1_, of the Ca II H and Kemission lines observed on high-dispersion spectra of 28chromospherically active binary systems (RS CVn and BY Dra stars) and 18single active stars. We test the width-luminosity correlations (theWilson-Bappu (WB) effect, and (W_1_, M_V_)) in these very active starsand analyse the influence of the activity level (I_K_3__) and therotational broadening (Vsin i) in these correlations. We have found thatfor very active stars the emission widths, both W_0_ and W_1_, arelarger than expected from previously accepted width-luminosityrelations. The stars with strong emission intensities, I_K_3__, andlarge values of Vsin i seem to present larger values of W_0_ thanresulted from WB relation, the effect of the rotational velocity beingthe most remarkable. On the contrary, W_1_ is strongly influenced byI_K_3__ but the effect of the rotational broadening is lesser. We alsoanalyse the behaviour of the Ca II H and K line parameters in these veryactive stars in relation with less active stars and we found that theincrease of W_1_ and I_K_1__ with I_K_3__ presents a flattening for themost active stars which is different for each value of W_0_. Finally wealso find a Hɛ width-luminosity correlation in the stars of thesample in which this emission line is present.
| UBV photometry of barium stars
Magnitudes in V and B-V and U-B colors observed by the 91-cm telescopeat Okayama are presented for 109 stars including both classical andmarginal barium stars. The two-color diagram shows a fair amount ofspread. This can be interpreted by interstellar reddening and variableamounts of line blocking effect. Both classical and marginal bariumstars form a fairly homogeneous group.
| Stellar activity in barium stars. I - Analysis of H and K CA II lines in ten barium stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1992AJ....103.1374C&db_key=AST
| Taxonomy of barium stars
Spectral classification, barium intensity, radial velocity, luminosity,and kinematical properties are determined for 389 barium stars byanalyzing image-tube spectra and photometric observation data. Diskkinematics for the stars are based on whether they are Ba weak or Bastrong. Weak barium stars in general have smaller velocity dispersions,brighter apparent magnitude, and lower luminosity than strong bariumstars. These characteristics are confirmed by solving for meanspectroscopic distances, z-scale height distances, and reduced propermotions.
| Kinematic and spatial distributions of barium stars - Are the barium stars and AM stars related?
The possibility of an evolutionary link between Am stars and bariumstars is considered, and an examination of previous data suggests thatbarium star precursors are main-sequence stars of intermediate mass, aremost likely A and/or F dwarfs, and are intermediate-mass binaries withclose to intermediate orbital separations. The possible role of masstransfer in the later development of Am systems is explored. Masstransfer and loss from systems with a range of masses and orbitalseparations may explain such statistical peculiarities of barium starsas the large dispersion in absolute magnitude, the large range ofelemental abundances from star to star, and the small number of starswith large peculiar velocities.
| Photoelectric photometry of carbon and barium stars in the Vilnius seven-color system and their color excesses
Not Available
| 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.
| A catalog of spectral classification and photometry of barium stars
Many other Ba II stars have been found, since the enhancement of theline of singly ionized barium (4554 A) in late-type, high-luminositystars was discovered by Bidelman and Keenan (1951). The majority ofstars so identified are listed in a study conducted by MacConnell et al.(1972). MacConnell et al. identified 150 'certain' barium stars and anadditional 90 'marginal' barium stars from inspection of objective-prismplates of the Michigan Spectral Survey of the southern sky. Since themajority of known Ba II stars were discovered with objective-prismplates, they have lacked high-quality spectral classifications. It hasbeen attempted to obtain these data along with broad- andintermediate-band photometry, in order to study the properties of thissubgroup of stars in greater detail than has heretofore been possible.Except for the stars recently identified by Bidelman (1981), the list ofspectroscopic and photometric data in Table 1 includes virtually allrecognized barium stars. The stars identified by Bidelman are listed inTable 2.
| Spectrophotometry of barium, CH and R type carbon stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..993G&db_key=AST
| Absolute magnitudes of barium stars based on the width of H alpha in absorption.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..537K&db_key=AST
| UVBY photometry of AM and AP stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..192W&db_key=AST
| The absolute magnitudes of the barium stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..384M&db_key=AST
| New Peculiar Stars Noted on Objective-Prism Plates
Not Available
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| קבוצת-כוכבים: | פגסוס |
| התרוממות ימנית: | 21h10m33.53s |
| סירוב: | +16°58'46.4" |
| גודל גלוי: | 8.011 |
| מרחק: | 222.717 פארסק |
| תנועה נכונה: | 29 |
| תנועה נכונה: | 9.4 |
| B-T magnitude: | 9.606 |
| V-T magnitude: | 8.143 |
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