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s-Process in low metallicity Pb stars.
We consider a sample of very metal-poor, C-rich, s-rich and lead-richstars observed at high-resolution spectroscopy, and some recentspectroscopic data of C+s-rich stars obtained at moderate resolution.The spectroscopic data of these stars are interpreted with AGBtheoretical models of different 13C-pocket efficiencies,initial mass and initial r-enrichment. When lead is not measured we giveour theoretical prediction. The observed stars are not on the AGB phase,but are main sequence or giant stars. They acquired the C and senrichments by mass transfer in a close binary system from the moremassive companion while on the AGB (now a white dwarf). A considerablefraction of the stars show both high s and r enrichments. To explain thes+r enriched stars we assume a parental cloud already enriched inr-elements. The measurement of Nb is an indicator of an extrinsic AGB ina binary system. The intrinsic indicator [hs/ls] constrains the initialmass, while [Pb/hs] and [Pb/ls] are a measure of the s-processefficiency. The apparent discrepancies of C and N abundances may bereconciled by assuming a strong cool bottom process occurring during theAGB. An important primary production of light elements, from Ne to Si,increasing with the star mass, is predicted for AGB models at very lowmetallicity, induced by n capture on primary 22Ne and itsprogenies.
| Speckle interferometry of nearby multiple stars. III.
Not Available
| Carbon Stars in the Infrared Telescope in Space Survey
We have identified 139 cool carbon stars in the near-infraredspectrophotometric survey of the Infrared Telescope in Space (IRTS) fromthe conspicuous presence of molecular absorption bands at 1.8, 3.1, and3.8 μm. Among them, 14 are new bright (K~4.0-7.0) carbon stars. Wefind a trend relating the 3.1 μm band strength to the K-L'color index, which is known to correlate with mass-loss rate. This couldbe an effect of a relation between the depth of the 3.1 μm featureand the degree of development of the extended stellar atmosphere wheredust starts to form.
| First stars IV. CS 29497-030: Evidence for operation of the s-process at very low metallicity
We present an abundance analysis of the very metal-poor, carbon-enhancedstar CS 29497-030. Our results indicate that this unusually hot turnoffstar (Teff = 6650 K, log g = 3.5) has a metallicity [Fe/H] =-2.8, and exhibits large overabundances of carbon ([C/Fe] = +2.38),nitrogen ([N/Fe] = +1.88), and oxygen ([O/Fe] = +1.67). This star alsoexhibits a large enhancement in its neutron-capture elements; thepattern follows that expected to arise from the s-process. Inparticular, the Pb abundance is found to be very high with respect toiron ([Pb/Fe] = +3.5), and also with respect to the second peaks-process elements (e.g., Ba, La, Ce, Nd), which fits into the newlyintroduced classification of lead (Pb) stars. The known spectroscopicbinary status of this star, along with the observed s-process abundancepattern, suggest that it has accreted matter from a companion, whichformerly was an Asymptotic Giant-Branch (AGB) star. In a preliminaryanalysis, we have also identified broad absorption lines of metallicspecies that suggest a large axial rotational velocity for this star,which may be the result of spin-up associated with the accretion ofmaterial from its previous AGB companion. In addition, this star isclearly depleted in the light element Li. When considered along with itsrather high inferred temperature, these observations are consistent withthe expected properties of a very low metallicity halo blue straggler.Based on observations made with the ESO Very Large Telescope at ParanalObservatory, Chile (program ID 165.N-0276(A)).Table \ref{tab6} is only available in electronic form athttp://www.edpsciences.org
| Lead and mathbf s-process elements in stars of various metallicities: AGB predictions compared with observation
We present AGB predictions for all heavy elements within a large rangeof 13C-pocket efficiencies for stars of differentmetallicities, and compare them in detail with a number of spectroscopicobservations of s-rich and lead-rich in the Galaxy. The current conceptof the s-process efficiency, specified by the [hs/ls] index, is shown tobe inappropriate for the metal poor AGB stars and a second independentindex, [Pb/hs] or [Pb/ls], needs to be introduced. The state-of-the-artconcerning the interpretation of lead stars allows a very large spreadof [Pb/hs] in metal poor stars, as typically observed. We discussagreements and discrepancies for a large range of elements.
| An attempt to derive Mg isotopic ratios in carbon stars
We discuss the use of the spectral range near 7570 Å todetermine the Mg isotopic ratios in carbon stars using theB'2 Sigma +-X 2 Sigma + system of the MgH molecule. We also compare with thespectral range near 5140 Å that has been commonly used in normalstars (oxygen-rich stars). The region near 5140 Å is not thebetter choice for carbon stars because it is very crowded with CN andC_2 molecular bands and the localization of the continuum iscomplicated. The range near 7570 Å is less blended withmolecular bands. The continuum is easy to locate and the isotopicsplitting between MgH isotopic absorptions is larger. Unfortunately, weare not able to reproduce accurately the observed spectrum in thisregion and, moreover, the synthetic spectrum is not sensitive to largevariations in the isotopic ratios.
| More lead stars
The standard model for the operation of the s-process in asymptoticgiant branch (AGB) stars predicts that low-metallicity ([Fe/H] <~ -1)AGB stars should exhibit large overabundances of Pb and Bi as comparedto other s-elements. The discovery of the first three such ``leadstars'' (defined as stars enriched in s-elements with [Pb/hs] >~ 1,hs being any of Ba, La or Ce) among CH stars has been reported in aprevious paper (Van Eck et al. \cite{VanEck-01}). Five more CH stars(with [Fe/H] ranging from -1.5 to -2.5) are studied in the presentpaper, and two of them appear to be enriched in lead (with [Pb/Ce] =~0.7). The Pb I line at lambda4057 .812 Å is detected and clearlyresolved thanks to high-resolution spectra (R = lambda /Delta lambda =135ts000 ). The abundances for these two stars (HD 198269 and HD 201626)are consistent with the predictions for the s-process operating inlow-metallicity AGB stars as a consequence of the ``partial mixing'' ofprotons below the convective hydrogen envelope. Another two stars (HD189711 and V Ari) add to a growing number of low-metallicity stars (alsoincluding LP 625-44 and LP 706-7, as reported by Aoki et al.\cite{Aoki2001}) which do not conform to these predictions. Variationson the canonical proton-mixing scenario for the operation of thes-process in low-metallicity stars, that could account for thesediscrepant stars, are briefly discussed.Based on observations carried out at the European Southern Observatory(La Silla, Chile; Program 65.L-0354) and at the Observatoire de HauteProvence (operated by CNRS, France).
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| Spectral Classification of Faint Carbon Stars
R--N classification of 187 faint carbon stars is based on the classicalcriteria adjusted to the yellow-red spectral region, with two newcriteria added -- the ratios of the red CN bands 6206/6332 (Å) and6478/6631 (Å).
| 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
| Nucleosynthesis and Mixing on the Asymptotic Giant Branch. III. Predicted and Observed s-Process Abundances
We present the results of s-process nucleosynthesis calculations forasymptotic giant branch (AGB) stars of different metallicities anddifferent initial stellar masses (1.5 and 3 Msolar), and wepresent comparisons of them with observational constraints fromhigh-resolution spectroscopy of evolved stars over a wide metallicityrange. The computations were based on previously published stellarevolutionary models that account for the third dredge-up phenomenonoccurring late on the AGB. Neutron production is driven by the13C(α,n)16O reaction during the interpulseperiods in a tiny layer in radiative equilibrium at the top of the He-and C-rich shell. The neutron source 13C is manufacturedlocally by proton captures on the abundant 12C; a few protonsare assumed to penetrate from the convective envelope into the radiativelayer at any third dredge-up episode, when a chemical discontinuity isestablished between the convective envelope and the He- and C-richzones. A weaker neutron release is also guaranteed by the marginalactivation of the reaction 22Ne(α,n)25Mgduring the convective thermal pulses. Owing to the lack of a consistentmodel for 13C formation, the abundance of 13Cburnt per cycle is allowed to vary as a free parameter over a wideinterval (a factor of 50). The s-enriched material is subsequently mixedwith the envelope by the third dredge-up, and the envelope compositionis computed after each thermal pulse. We follow the changes in thephotospheric abundance of the Ba-peak elements (heavy s [hs]) and thatof the Zr-peak ones (light s [ls]), whose logarithmic ratio [hs/ls] hasoften been adopted as an indicator of the s-process efficiency (e.g., ofthe neutron exposure). Our model predictions for this parameter show acomplex trend versus metallicity. Especially noteworthy is theprediction that the flow along the s-path at low metallicities drainsthe Zr and Ba peaks and builds an excess at the doubly magic208Pb, which is at the termination of the s-path. We thendiscuss the effects on the models of variations in the crucialparameters of the 13C pocket, finding that they are notcritical for interpreting the results. The theoretical predictions arecompared with published abundances of s-elements for AGB giants ofclasses MS, S, SC, post-AGB supergiants, and for various classes ofbinary stars, which supposedly derive their composition by mass transferfrom an AGB companion. This is done for objects belonging both to theGalactic disk and to the halo. The observations in general confirm thecomplex dependence of neutron captures on metallicity. They suggest thata moderate spread exists in the abundance of 13C that isburnt in different stars. Although additional observations are needed,it seems that a good understanding has been achieved of s-processoperation in AGB stars. Finally, the detailed abundance distributionincluding the light elements (CNO) of a few s-enriched stars atdifferent metallicities are examined and satisfactorily reproduced bymodel envelope compositions.
| The effective temperatures of carbon-rich stars
We evaluate effective temperatures of 390 carbon-rich stars. Theinterstellar extinction on their lines of sights was determined andcircumstellar contributions derived. The intrinsic (dereddened) spectralenergy distributions (SEDs) are classified into 14 photometric groups(HCi, CVj and SCV with i=0,5 and j=1,7). The newscale of effective temperatures proposed here is calibrated on the 54angular diameters (measured on 52 stars) available at present from lunaroccultations and interferometry. The brightness distribution on stellardiscs and its influence on diameter evaluations are discussed. Theeffective temperatures directly deduced from those diameters correlatewith the classification into photometric groups, despite the large errorbars on diameters. The main parameter of our photometric classificationis thus effective temperature. Our photometric < k right >1/2 coefficients are shown to be angular diameters on arelative scale for a given photometric group, (more precisely for agiven effective temperature). The angular diameters are consistent withthe photometric data previously shown to be consistent with the trueparallaxes from HIPPARCOS observations (Knapik, et al. \cite{knapik98},Sect. 6). Provisional effective temperatures, as constrained by asuccessful comparison of dereddened SEDs from observations to modelatmosphere predictions, are in good agreement with the values directlycalculated from the observed angular diameters and with those deducedfrom five selected intrinsic color indices. These three approaches wereused to calibrate a reference angular diameter Phi 0 and theassociated coefficient CT_eff. The effective temperatureproposed for each star is the arithmetic mean of two estimates, one(``bolometric'') from a reference integrated flux F0, theother (``spectral'') from calibrated color indices which arerepresentative of SED shapes. Effective temperatures for about 390carbon stars are provided on this new homogeneous scale, together withvalues for some stars classified with oxygen-type SEDs with a total of438 SEDs (410 stars) studied. Apparent bolometric magnitudes are given.Objects with strong infrared excesses and optically thick circumstellardust shells are discussed separately. The new effective temperaturescale is shown to be compatible and (statistically) consistent with thesample of direct values from the observed angular diameters. Theeffective temperatures are confirmed to be higher than the mean colortemperatures (from 140 to 440 K). They are in good agreement with thepublished estimates from the infrared flux method forTeff>= 3170 K, while an increasing discrepancy is observedtoward lower temperatures. As an illustration of the efficiency of thephotometric classification and effective temperature scale, the C/Oratios and the Merrill-Sanford (M-S) band intensities are investigated.It is shown that the maximum value, mean value and dispersion of C/Oincrease along the photometric CV-sequence, i.e. with decreasingeffective temperature. The M-S bands of SiC2 are shown tohave a transition from ``none'' to ``strong'' at Teff =~(2800+/- 150right ) K. Simultaneously, with decreasing effectivetemperature, the mean C/O ratio increases from 1.04 to 1.36, thetransition in SiC2 strength occurring while 1.07<= C/O<= 1.18. This research has made use of the Simbad database operatedat CDS, Strasbourg, France. Table 10 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)}or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/369/178
| General Catalog of Galactic Carbon Stars by C. B. Stephenson. Third Edition
The catalog is an updated and revised version of Stephenson's Catalogueof Galactic Cool Carbon Stars (2nd edition). It includes 6891 entries.For each star the following information is given: equatorial (2000.0)and galactic coordinates, blue, visual and infrared magnitudes, spectralclassification, references, designations in the most significantcatalogs and coordinate precision classes. The main catalog issupplemented by remarks containing information for which there was noplace in entries of the main part, as well as some occasional notesabout the peculiarities of specific stars.
| Heavy-element abundances in the CH/CN-strong very metal-poor stars CS 22948-27 and CS 29497-34
We have carried out a new analysis of the very metal-poor CH/CN strongstars CS 22948-27 and CS 29497-34. In particular, the effectivetemperatures were recomputed by comparing newly obtained photometricdata to colours derived from model atmospheres computed especially forthese stars. Metallicities of [Fe/H] = -2.45 and -2.90 are found,respectively, for CS 22948-27 and CS 29497-34. The abundances of heavyelements have been derived from newly obtained high-resolutionspectroscopy in the blue spectral region, together with previouslyobtained spectra in the red, resulting in a total wavelength coverage oflambda lambda 4000-8200 Ä. We find that the abundance patterns ofour stars reflect enrichment by the r-process (as indicated by a high Euabundance), as well as by the s-process, which could be due to a masstransfer episode from a companion crossing the AGB phase, although noclear evidence for binarity is indicated in the spectra obtained todate. Observations collected at the European Southern Observatory (ESO),La Silla, Chile.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Diffraction-limited speckle masking interferometry of binary stars with the SAO 6-m telescope.
Not Available
| Chemical Composition of the Halo Mira-Type Carbon Star V CRB
CNO and metal abundances have been derived for the metal-deficientcarbon Mira-type star V CrB using high resolution spectra analyzed bythe synthetic spectrum method. The atmosphere was calculated withcontinuum opacity sources and molecular opacity due to CO, CN, C_2, HCN,C_2H_2 and C_3. V CrB was found to be metal-deficient, with [Fe/H] =--2.12. The CNO abundances are log A(C) = 7.17, log A(N) = 5.3 and logA(O) = 7.13. The carbon isotopic abundance ratio is (12) C/(13) C =10.5+/-5.0. Abundances of the s-process elements are enhanced. Theabundance pattern is similar to other late-type CH stars. A comparisonof the observed and computed near-infrared spectra indicates the need ofimproving the C_2H_2 opacity data.
| Carbon isotope ratio in carbon stars of the galactic halo.
We analysed CN red system (~8000Å) and C_2_ Swan system(~4700Å) to know carbon isotope ratios (^12^C/^13^C) for carbonstars in the Galactic halo, named CH stars. The isotope ratios areobtained for 6 CH stars by the curve-of-growth analysis of the isolated^12^CN and ^13^CN lines. In this analysis, we compared directly ^12^CNand ^13^CN lines of similar intensities (iso-intensity method), and theresulting ^12^C/^13^C ratios are almost independent of the modelatmosphere and its parameters. The ^13^CN lines appear to be too weak insome CH stars, for which we applied the spectral synthesis method to thestronger C_2_ Swan band, obtained ^12^C/^13^C ratios for two stars andestimated the lower limits of ^12^C/^13^C ratios for two stars. In thiscase, however, the results depend on model atmosphere and itsparameters. Results from our present and previous works show that mostof them (12 stars) distribute around ^12^C/^13^C~10 and two stars havevery high values (^12^C/^13^C>=500). The distribution of ^12^C/^13^Cratios in CH stars is different from that of the population I carbonstars as well as population II oxygen-rich giants (G~K types). The CHstars of very high ^12^C/^13^C ratios can be explained by dredge-up of^12^C due to 3α-process as in population I carbon stars (N-type).On the other hand the formation of the CH stars with low ^12^C/^13^Cratios requires the large supply of ^12^C followed by a process ofdecreasing ^12^C/^13^C ratio.
| Abundances in the symbiotic star AG Draconis: the barium-symbiotic connection.
An abundance analysis of the yellow symbiotic system AG Draconis revealsit to be a metal-poor K-giant ([Fe/H]=-1.3) which is enriched in theheavy s-process elements. This star thus provides a link between thesymbiotic stars and the binary barium and CH stars which are alsos-process enriched. These binary systems, which exhibit overabundancesof the heavy elements, owe their abundance peculiarities to masstransfer from thermally-pulsing asymptotic giant branch stars, whichhave since evolved to become white-dwarf companions of the cool stars wenow view as the chemically peculiar primaries. A comparison of theheavy-element abundance distribution in AG Dra with theoreticalnucleosynthesis calculations shows that the s-process is defined by arelatively large neutron exposure (τ=1.3mb^-1^), while an analysisof the rubidium abundance suggests that the s-process occurred at aneutron density of about 2x10^8^cm^-3^. The derived spectroscopic orbitof AG Dra is similar to the orbits of barium and CH stars. Because theluminosity function of low-metallicity K giants is skewed towards higherluminosities by about 2 magnitudes relative to solar-metallicity giants,it is argued that the lower metallicity K giants have larger mass-lossrates. It is this larger mass-loss rate that drives the symbioticphenomena in AG Dra and we suggest that the other yellow symbiotic starsare probably low-metallicity objects as well.
| Chemical composition of metal-poor carbon stars in the halo.
In an attempt to increase the sample of metal-deficient late-type (i.e.cool) halo carbon stars analysed (only 3 such stars have previously beenanalysed spectroscopically), we obtained high-resolution visual spectraof 5 more candidates (and analysed in addition existing archive IRspectra for one of the stars) from the recent catalogue of Sleivyt e& Bartkevicius (1990), HD 25408 (C5,3J), HD 42272 (C5,4 CH), HD59643 (C6,2CH), HD 189711 (C4,3 CH) and HD 197604 (C4,2 CH). From thespectra we have derived C/O ratios, N/C ratios, and metal abundances. Ifthe oxygen abundance was fixed at logA(O)=7.4/8.3 (assuming that itfollows the trend of oxygen overabundance relative to iron found in halostars in general) we can furthermore derive [C/Fe] and [N/Fe]. New modelatmospheres of metal-poor carbon stars were calculated with continuumopacity sources and molecular lines of CO, CN, C_2_, HCN, C_2_H_2_ andC_3_. Two of the stars, HD 25408 and HD 42272, turned out not to be CHstars. The other three stars, although late-type, showed the C/O and[Fe/H] ratios common in early-type CH stars. From the total sample ofthe six confirmed cool halo-CH stars now analysed, we find evidence thatnot all metal-poor low mass halo carbon stars can have formed due tomass transfer in binary systems, as is usually assumed. At least 3 ofthe stars, and possible more, are likely to have formed as intrinsiccarbon stars, with some similarities to the carbon star population inthe dwarf galaxies.
| A New Version of the Catalog of CH and Related Stars (CH95 Catalog)
A new version of the catalog of CH and related stars contains 244 fieldstars and 17 globular cluster stars. Here a list of these stars withtheir coordinates, their positions in the HR diagram and somestatistical diagrams is presented. The catalog will soon be available inthe printed and computerized versions.
| Classification of Population II Stars in the Vilnius Photometric System. I. Methods
The methods used for classification of Population II stars in theVilnius photometric system are described. An extensive set of standardswith known astrophysical parameters compiled from the literature sourcesis given. These standard stars are classified in the Vilnius photometricsystem using the methods described. The accuracy of classification isevaluated by a comparison of the astrophysical parameters derived fromthe Vilnius photometric system with those estimated from spectroscopicstudies as well as from photometric data in other systems. For dwarfsand subdwarfs, we find a satisfactory agreement between our reddeningsand those estimated in the uvbyscriptstyle beta system. The standarddeviation of [Fe/H] deter mined in the Vilnius system is about 0.2 dex.The absolute magnitude for dwarfs and subdwarfs is estimated with anaccuracy of scriptstyle <=0.5 mag.
| 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.
| Binary star speckle measurements during 1989-1993 from the SAO 6 M and 1 M telescopes in Zelenchuk
We have continued to survey visual and interferometric binary stars withsignificant orbital motion by means of speckle method at the telescopesof the Special Astrophysical Observatory (SAO) in Zelenchuk. Here wepresent the lists of 267 speckle observations made with the 6 m and the1 m telescopes in the period May 1989-November 1993.
| Spectroscopic study of carbon stars with silicate features. 1: Observations
The results of an optical spectroscopic study of carbon stars withsilicate feature done at the Dominion Astrophysical Observatory (DAO) inVictoria in 1991 is presented. Four stars are confirmed to be C-13-richcarbon stars (J stars). Two stars are provisionally identified as Jstars. A preliminary spectral analysis is carried out. Two groups of Jstars were found in the IRAS color-color diagram. The 'red group'contains carbon stars with silicate emission feature which are good Jstar candidates; and the 'vertical strip group' contains standard Jstars which show weak or no SiC feature. It is suggested that thesources in the 'red group' represent the higher mass members of theasymptotic giant branch population. The enhancement of C-13 may beexplained by the envelope burning mechanism.
| A very high C-12/C-13 ratio in some CH stars - Implications for dredge-up in AGB evolution during the metal-poor ERA
Abstract image available at:http://adsabs.harvard.edu/abs/1991A&A...252L...1T
| Carbon stars at high Galactic latitude
Photometry and kinematics are presented for a sample of objective prismselected carbon stars toward the north and south Galactic poles.Distances are determined by fitting the infrared colors to a giantbranch. If these stars are like the carbon stars seen in dwarfspheroidal galaxies, the median distance of the sample is 28 kpc. Ifthey are more like the carbon stars found recently in the Galacticbulge, they may be only half as distant. The surface density of carbonstars as a function of distance is remarkably consistent with an R exp1/4 density profile for the Galactic halo. This density profile can betraced to about 15 scale radii and fills a volume similar to thatoccupied by globular clusters. The data yields an effective radius ofeither 7.0 or 3.5 kpc depending on choice of distance scale. Thevelocity dispersion of the sample is 96 + or - 12 km/s. A kinematicmodel in which vertical velocity dispersion is independent of heightabove the Galactic plane seems in best accord with the data.
| Catalogue of CH and metal-deficient barium stars
Not Available
| A general catalogue of cool carbon stars
Not Available
| Spectrophotometric investigation of carbon stars
Not Available
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Osservazione e dati astrometrici
| Costellazione: | Aquila |
| Ascensione retta: | 20h01m03.79s |
| Declinazione: | +09°30'51.2" |
| Magnitudine apparente: | 8.429 |
| Distanza: | 574.713 parsec |
| Moto proprio RA: | -11.1 |
| Moto proprio Dec: | -22.2 |
| B-T magnitude: | 11.052 |
| V-T magnitude: | 8.646 |
Cataloghi e designazioni:
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