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On the nature of lithium-rich giant stars. Constraints from beryllium abundances
We have derived beryllium abundances for 7 Li-rich giant (A(Li) >1.5) stars and 10 other Li-normal giants with the aim of investigatingthe origin of the lithium in the Li-rich giants. In particular, we testthe predictions of the engulfment scenario proposed by Siess & Livio(1999, MNRAS, 308, 1133), where the engulfment of a brown dwarf or oneor more giant planets would lead to simultaneous enrichment of7Li and 9Be. We show that regardless of theirnature, none of the stars studied in this paper were found to havedetectable beryllium. Using simple dilution arguments we show thatengulfment of an external object as the sole source of Li enrichment isruled out by the Li and Be abundance data. The present results favor theidea that Li has been produced in the interior of the stars by aCameron-Fowler process and brought up to the surface by an extra mixingmechanism.
| 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}
| On the Wilson-Bappu relationship in the Mg II k line
An investigation is carried out on the Wilson-Bappu effect in the Mg Iik line at 2796.34 Å. The work is based on a selection of 230 starsobserved by both the IUE and HIPPARCOS satellites, covering a wide rangeof spectral types (F to M) and absolute visual magnitudes (-5.4<=MV <=9.0). A semi-automatic procedure is used to measurethe line widths, which applies also in the presence of strong centralabsorption reversal. The Wilson-Bappu relationship here provided isconsidered to represent an improvement over previous recent results forthe considerably larger data sample used, as well as for a properconsideration of the measurement errors. No evidence has been found fora possible dependence of the WB effect on stellar metallicity andeffective temperature.
| Two K Giants with Supermeteoritic Lithium Abundances: HDE 233517 and HD 9746
Two unusual Li-rich K giants, HDE 233517 and HD 9746, have been studied.Optical spectroscopy and photometry have been obtained to determine thefundamental parameters of HDE 233517, a single K2 III with an extremelylarge infrared excess. The spectra yield Teff=4475 K,logg=2.25, [Fe/H]=-0.37, vsini=17.6 km s-1, and a non-LTElogɛ(7Li)=4.22. Photometric observations reveallow-amplitude light variability with a period of 47.9 days. Combinedwith other parameters, this results in a minimum radius of 16.7Rsolar and minimum distance of 617 pc. Comparison of spectraobtained in 1994 and 1996 show profile variations in Hα and the NaD lines indicative of changing mass loss. Optical spectra of HD 9746, achromospherically active giant, were analyzed. The Teff=4400K and revised Hipparcos-based gravity of logg=2.30 lead to a non-LTElogɛ(7Li)=3.75. The Li abundances in both stars aresupermeteoritic. By the inclusion and exclusion of 6Li in thesyntheses, we show that consistent 7Li abundances areobtained only when 6Li is absent in the synthetic fit. Thisprovides evidence for fresh 7Li production and excludes bothpreservation of primordial Li and planetary accretion as viablescenarios for the formation of Li-rich giants. Both stars lie in closeproximity to the red giant luminosity bump supporting the hypothesisthat 7Li production is caused by the same mixing mechanismthat later results in CN processing and lowers the12C/13C ratio to nonstandard values.
| Rotation and lithium in single giant stars
In the present work, we study the link between rotation and lithiumabundance in giant stars of luminosity class III, on the basis of alarge sample of 309 single stars of spectral type F, G and K. We havefound a trend for a link between the discontinuity in rotation at thespectral type G0III and the behavior of lithium abundances around thesame spectral type. The present work also shows that giant starspresenting the highest lithium contents, typically stars earlier thanG0III, are those with the highest rotation rates, pointing for adependence of lithium content on rotation, as observed for otherluminosity classes. Giant stars later than G0III present, as a rule, thelowest rotation rates and lithium contents. A large spread of about fivemagnitudes in lithium abundance is observed for the slow rotators.Finally, single giant stars with masses 1.5 < M/Msun<=2.5 show a clearest trend for a correlation between rotational velocityand lithium abundance. Based on observations collected at theObservatoire de Haute -- Provence (France) and at the European SouthernObservatory, La Silla (Chile). Table 2 is only available electronicallywith the On-Line publication athttp://link.springer.de/link/service/00230/
| The Nature of the lithium rich giants. Mixing episodes on the RGB and early-AGB
We present a critical analysis of the nature of the so-called Li-richRGB stars. For a majority of the stars, we have used Hipparcosparallaxes to determine masses and evolutionary states by comparingtheir position on the Hertzsprung-Russell diagram with theoreticalevolutionary tracks. Among the twenty Li-rich giants whose location onthe HR diagram we were able to determine precisely, five appear to beLi-rich because they have not completed the standard first dredge-updilution, and three have abundances compatible with the maximum allowedby standard dilution. Thus, these should be re-classified as Li-normal.For the remaining stars, the high Li abundance must be a result of freshsynthesis of this fragile element. We identify two distinct episodes ofLi production which occur in advanced evolutionary phases depending uponthe mass of the star. Low-mass RGB stars, which later undergo the heliumflash, produce Li at the phase referred to as the bump in the luminosityfunction. At this evolutionary phase, the outwardly-moving hydrogenshell burns through the mean molecular weight discontinuity created bythe first dredge-up. Any extra-mixing process can now easily connect the3He-rich envelope material to the outer regions of thehydrogen-burning shell, enabling Li production by the Cameron &Fowler (1971) process. While very high Li abundances are then reached,this Li-rich phase is extremely short lived because once the mixingextends deep enough to lower the carbon isotopic ratio below thestandard dilution value, the freshly synthesized Li is quicklydestroyed. In intermediate-mass stars, the mean molecular weightgradient due to the first dredge-up is not erased until after the starhas begun to burn helium in its core. The Li-rich phase in these starsoccurs when the convective envelope deepens at the base of the AGB,permitting extra-mixing to play an effective role. Li production ceaseswhen a strong mean molecular weight gradient is built up between thedeepening convective envelope and the shell of nuclear burning thatsurrounds the inert CO core. This episode is also very short lived.Low-mass stars may undergo additional mixing at this phase. The compileddata provide constraints on the time scales for extra mixing and someinsight on processes suggested in the literature. However, our resultsdo not suggest any specific trigger mechanism. Since the Li-rich phasesare extremely short, enrichment of the Li content of the ISM as a resultof these episodes is negligible.
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Statistical equilibrium of lithium in the atmospheres of late-type stars: lithium-rich G-K giants.
Not Available
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Kinematics and stellar populations in active galaxies: the LINER NGC 4579 (M58).
We present long slit spectroscopy from the blue to the near-IR of theLINER galaxy NGC 4579 (M58). Stellar indices are used as tools toinvestigate if any differences in the kinematics and/or stellar contentexist between the nucleus and the circumnuclear regions of the galaxy.Blue indices are found to be affected by contamination due to emissionlines in the central region and the method to measure these indices isdiscussed. No peculiarities are found in the stellar kinematics withrespect to the bulges of normal spirals, whose old population can fitthe observations of the bulge of NGC 4579. Alternatively, the lowcentral values of Mg_2_ and the high values of Mg_1_ in the blue and MgIin the near-IR lead us to propose the dominant bulge stellar populationin NGC 4579 to be substantially younger than the one present in ordinaryellipticals and S0 galaxies, and therefore a population with an age ofabout (2.5+/-1)Gyr. and a metallicity of (1.5+/-0.5)Zsun_ isalso able to reproduce simultaneously the studied spectral indices aswell as the optical spectral energy distribution of the nucleus of NGC4579.
| Lithium Enrichment--Mass-Loss Connection in K Giant Stars
Based on observed far-infrared properties of K giant stars, we propose ascenario linking the high Li abundances of some of these stars to theevolution of circumstellar shells. In this model, every K giant withmasses between 1.0 and 2.5 Mȯ become Li rich during the red giantbranch stage, and the internal mechanism responsible for the Lienrichment will initiate a prompt mass-loss event. The evolutionarypaths of the detached shells are compatible with observations for lowexpansion velocities of the order of 2 km s-1 and mass loss of (2--5) x10-8 Mȯ yr-1. This modest mass loss is, however, 2 orders ofmagnitude larger than those of normal, Li-poor K giants. A "Li time" ofthe order of 80,000 yr or somewhat larger is possible. This Li phase is,nevertheless, not related to the 12C/13C ratio which appears to evolve,for these low-mass stars, over a much longer time. This model requires arapid internal process of Li enrichment and depletion. New argumentsappearing in the literature concerning this internal process arediscussed. Reference is also made to the importance of these stars tothe Galactic Li evolution.
| The photoelectric astrolabe catalogue of Yunnan Observatory (YPAC).
The positions of 53 FK5, 70 FK5 Extension and 486 GC stars are given forthe equator and equinox J2000.0 and for the mean observation epoch ofeach star. They are determined with the photoelectric astrolabe ofYunnan Observatory. The internal mean errors in right ascension anddeclination are +/- 0.046" and +/- 0.059", respectively. The meanobservation epoch is 1989.51.
| Rotational velocity for lithium-rich evolved stars.
Precise rotational velocities have been determined for 12 lithium-richgiant stars using the CORAVEL spectrometer. Except for HD 9746, thelithium-rich giants show normal rotational velocities with respect totypical lithium-normal giants of the same spectral type. Further, wehave found no sign of binarity for the lithium-rich giants.
| Li-rich giants: evidence for convection mixing
Not Available
| The Li K giant stars
Not Available
| Carbon Isotope Ratios in Very Lithium-Rich K Giants
High-resolution spectra were used to derive CNO abundances and the12C/13C ratios for the very Li-rich K giants HD 19745 and HD 39853. Oand 12C/13C are also obtained for comparison for the Li-rich K giant HD787. Results from the literature for other very Li-rich giants were alsogathered to allow for a more complete discussion. The three most Li-richgiants known, HD 19745, HD 39853, and HD 95799, with epsilon (Li) >=3.0, show low 12C/13C values (12C/13C <= 15), requiring anextra-mixing mechanism, whereas HD 9746 and HD 112127 with epsilon (Li)~ 2.7 show 12C/13C ~ 25, following the standard first dredge-uppredictions. The data for these five stars indicate that no clearcorrelation is found between 12C/13C and epsilon (Li) for the veryLi-rich giants. An important conclusion is that, since for the threemost Li-rich giants, 12C/13C is low, efficient mixing should havelowered both 12C/13C and Li abundances. The very high Li abundancesactually found in these stars call therefore for an independentmechanism enriching the Li.
| 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.
| CNO Abundances and 12/C/13/C Ratios in the Atmospheres of Lithium-Rich Giants
Not Available
| A revised effective-temperature calibration for the DDO photometric system
A revised effective-temperature calibration for the David DunlapObservatory (DDO) photometric system is presented. Recently publishedphotometric and spectroscopic observations of field and open-cluster Gand K stars allow a better definition of the solar-abundance fiducialrelation in the DDO C0(45-48) vs. C0(42-45)diagram. The ability of the DDO system to predict MK spectral types of Gand K giants is demonstrated. The new DDO effective temperaturecalibration reproduces satisfactorily the infrared temperature scale ofBell and Gustafsson (1989). It is shown that Osborn's (1979) calibrationunderestimates the effective temperatures of K giants by approximately170 K and those of late-type dwarfs by approximately 150 K.
| Lithium and rapid rotation in chromospherically active single giants
The rotational velocities presently obtained via spectroscopicobservations of a group of moderately rapidly rotating, chomosphericallyactive single giants indicate that Gray's (1989) rotostat hypothesisrequires modification. Their rapid rotation appears to be due to high Liabundances, and results in increased chromospheric activity. A scenariois projected in which the surface convection zone reaches the rapidlyrotating core just as a star begins its first ascent of the giantbranch, and dredges both high angular momentum material and freshlysynthesized Li to the surface.
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances
A high-resolution spectroscopic survey of 671 G and K field giants isdescribed. Broad-band Johnson colors have been calibrated againstrecent, accurate effective temperature, T(eff), measurements for starsin the range 3900-6000 K. A table of polynomial coefficients for 10color-T(eff) relations is presented. Stellar atmosphere parameters,including T(eff), log g, Fe/H, and microturbulent velocity, are computedfor each star, using the high-resolution spectra and various publishedphotometric catalogs. For each star, elemental abundances for a varietyof species have been computed using a LTE spectrum synthesis program andthe adopted atmosphere parameters.
| Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars
Results are presented of an extensive X-ray survey of 380 giant andsupergiant stars of spectral types from F to M, carried out with theEinstein Observatory. It was found that the observed F giants orsubgiants (slightly evolved stars with a mass M less than about 2 solarmasses) are X-ray emitters at the same level of main-sequence stars ofsimilar spectral type. The G giants show a range of emissions more than3 orders of magnitude wide; some single G giants exist with X-rayluminosities comparable to RS CVn systems, while some nearby large Ggiants have upper limits on the X-ray emission below typical solarvalues. The K giants have an observed X-ray emission level significantlylower than F and F giants. None of the 29 M giants were detected, exceptfor one spectroscopic binary.
| A search for lithium-rich giant stars
Lithium abundances or upper limits have been determined for 644 brightG-K giant stars selected from the DDO photometric catalog. Two of thesegiants possess surface lithium abundances approaching the 'cosmic' valueof the interstellar medium and young main-sequence stars, and eight moregiants have Li contents far in excess of standard predictions. At leastsome of these Li-rich giants are shown to be evolved to the stage ofhaving convectively mixed envelopes, either from the direct evidence oflow surface carbon isotope ratios, or from the indirect evidence oftheir H-R diagram positions. Suggestions are given for the uniqueconditions that might have allowed these stars to produce or accrete newlithium for their surface layers, or simply to preserve from destructiontheir initial lithium contents. The lithium abundance of the remainingstars demonstrates that giants only very rarely meet the expectations ofstandard first dredge-up theories; the average extra Li destructionrequired is about 1.5 dex. The evolutionary states of these giants andtheir average masses are discussed briefly, and the Li distribution ofthe giants is compared to predictions of Galactic chemical evolution.
| Final catalogue of 229 photometric standards in UBV system near the selected areas 1-115
Not Available
| The corrected magnitudes and colours of 278 stars near S.A. 1-139 in the UBV system
Not Available
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| קבוצת-כוכבים: | נשר |
| התרוממות ימנית: | 19h29m22.10s |
| סירוב: | +14°35'45.0" |
| גודל גלוי: | 5.56 |
| מרחק: | 87.873 פארסק |
| תנועה נכונה: | 49.2 |
| תנועה נכונה: | -23.7 |
| B-T magnitude: | 6.907 |
| V-T magnitude: | 5.681 |
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