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Reprocessing the Hipparcos data of evolved stars. III. Revised Hipparcos period-luminosity relationship for galactic long-period variable stars
We analyze the K band luminosities of a sample of galactic long-periodvariables using parallaxes measured by the Hipparcos mission. Theparallaxes are in most cases re-computed from the Hipparcos IntermediateAstrometric Data using improved astrometric fits and chromaticitycorrections. The K band magnitudes are taken from the literature andfrom measurements by COBE, and are corrected for interstellar andcircumstellar extinction. The sample contains stars of several spectraltypes: M, S and C, and of several variability classes: Mira, semiregularSRa, and SRb. We find that the distribution of stars in theperiod-luminosity plane is independent of circumstellar chemistry, butthat the different variability types have different P-L distributions.Both the Mira variables and the SRb variables have reasonablywell-defined period-luminosity relationships, but with very differentslopes. The SRa variables are distributed between the two classes,suggesting that they are a mixture of Miras and SRb, rather than aseparate class of stars. New period-luminosity relationships are derivedbased on our revised Hipparcos parallaxes. The Miras show a similarperiod-luminosity relationship to that found for Large Magellanic CloudMiras by Feast et al. (\cite{Feast-1989:a}). The maximum absolute Kmagnitude of the sample is about -8.2 for both Miras and semi-regularstars, only slightly fainter than the expected AGB limit. We show thatthe stars with the longest periods (P>400 d) have high mass lossrates and are almost all Mira variables.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA \cite{Hipparcos}).Table \ref{Tab:data1} 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/403/993
| 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
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| 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.
| The PL relation of galactic carbon LPVs. The distance modulus to LMC
We present a period-luminosity (PL) diagram of 115 galactic carbon-richlong period variables (LPVs) observed by the HIPPARCOS satellite, in theform of the (MK,log P) relation. Our plot is compared to thediagram of carbon variables observed in the Large Magellanic Cloud(LMC). Both diagrams are found very similar and three samples aredelineated: long period variables close to the PL relation of Feast etal. (1989), short period-overluminous variables and a few underluminousLPVs, respectively Samples 1, 2 and 3. The used data were deduced fromexpectations of true parallaxes (Knapik et al. 1997) which arestatistically free of the Lutz-Kelker effect. The remaining bias due tothe non-gaussian distribution of absolute magnitudes is avoided: anon-linear parametric method is applied in Sect. 4 to the analysis ofthe PL relation for Sample 1 (72 LPVs). We obtainMK=(-3.99+/-0.13)log P+(2.07+/-0.15), in good agreement withthe slope found for LMC variables by Reid et al. (1995). The LMCdistance modulus then derived is mu =18.50+/-0.17. A well-defined upperlimit (ul) for long period stars in Sample 1 is found, with similarslopes in both the Galaxy (-4.85) and LMC (-4.72). No correction formetallicity was applied to the results. This research has made use ofthe Simbad database operated at CDS, Strasbourg, France.
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| Interstellar extinction and the intrinsic spectral distribution of variable carbon stars.
We present a new method of evaluation of the extinction by interstellardust on cool carbon variables. These late-type stars show no markedrelationship between spectral classification (the R, N- and C-types) andphotometric colour indices. The pair method is thus ruled out, at leastin the form currently in use for early-type or intermediate stars. Ourmethod makes use of the whole spectral energy distributions from UV toIR. A sample of 60 unreddened carbon variables is delineated and newcolour-colour diagrams are proposed where the reddening vector is nearlyperpendicular to their narrow intrinsic locus. Six photometric groups(or boxes : CV1 to 6) are derived among unreddened stars. They show acontinuous range of spectral energy distributions from "bluer" to"redder", and mean colour indices are obtained. A pair method isdescribed where each presumably reddened star is compared to these meanunreddened stars, a given extinction law being assumed. As anillustration, the results are shown for a sample of 133 well-documentedstars. The mean extinction law usually adopted for the diffuseinterstellar medium (R_V_=~3.1) is shown to provide good fits. Thethreshold for reddening detection turns to be E(B-V)=~0.02-0.03A goodcorrelation is observed when the derived colour excesses are compared tovalues from maps in the literature. The mean rate of visual extinctionamounts to =~1.25+/-1.1 , ranging from 0.37 nearl=~240° (intercloud) to 2.1 (cloud + intercloud) in two structurescorrelated with Gould's belt.
| The R Stars: Carbon Stars of a Different Kind
After $\sim$16 years of radial-velocity observations of a sample of 22R-type carbon stars, no evidence for binary motion has been detected inany of them. This is surprising considering that approximately 20\% ofnormal late-type giants are spectroscopic binaries, and the fraction isclose to 100\% in barium, CH, and subgiant/dwarf CH and barium stars. Itis suggested, therefore, that a process that has caused the mixing ofcarbon to the surface of these stars cannot act in a wide binary system.Possibly, the R stars were once all binaries, but with separations thatwould not allow them to evolve completely up the giant and asymptoticgiant branchs without coalescing. This coalescence may be the agentwhich causes carbon produced in the helium-core flash to be mixedoutwards to a region where convection zones can bring it to the surfaceof the star. (SECTION: Stars)
| A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..105..419B&db_key=AST
| Quantitative analysis of carbon isotopic ratios in carbon stars. I. 62 N-type and 15 SC-type carbon stars.
We present a result of quantitative analysis of ^12^C/^13^C ratios in 62N-type and 15 SC-type carbon stars. By the use of CCD as a detector wecan obtain spectra of resolution ~20,000 with enough signal-to-noiseratios for a large number of carbon stars, for which ^12^C/^13^C ratioshave not yet been derived. Carbon isotopic ratios are determined fromlines of the CN red system around 8000A, based on the iso-intensitymethod and line-blanketed model atmospheres. The average of ^12^C/^13^Cratios in 62 N-type carbon stars is found to be 27+/-11 (standarddeviation). The majority of the N-type carbon stars studied (about 85%)are found to have ^12^C/^13^C ratios less than 40, and the number ofstars which have ^12^C/^13^C ratios larger than 40 is found to berelatively small. This result shows a marked contrast to some of theprevious results that have shown the opposite distribution, namely,^12^C/^13^C ratios mostly larger than 40 in N-type carbon stars. Theaverage of ^12^C/^13^C ratios in 15 SC-type carbon stars is found to be22+/-14 (standard deviation). Most of the SC-type carbon stars studiedare found to have ^12^C/^13^C ratios larger than 10, while only three ofthem turn out to be ^13^C-rich. This is in contrast with the earlierclassification based on low resolution spectra which classified them asJ-type, that is, ^13^C-rich. The earlier temperature scale whichclassified SC-type carbon stars as the latest (C8-9) based on theirstrong NaI D lines can not be necessarily justified. The strong NaI Dlines of SC stars should be attributed to the peculiar atmosphericstructure due to C/O ratios very near to unity. The resulting^12^C/^13^C ratios are partly consistent with the scenario in which Mgiants evolve through SC-type to N-type carbon stars, as ^12^C producedduring the helium shell flash is added to the envelope.
| Spectral indexes of cool carbon stars in the near-infrared region. III.
Not Available
| 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.
| A Catalog of li Abundances and Equivalent Widths in a Sample of Galactic C-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102..361B&db_key=AST
| Analysis of IRAS stellar sources in Alpha Persei region
The present study is an analysis of IR sources in the Alpha Persei opencluster region from the IRAS Point Source Catalog and from ground-basedphotometric observations. Cross-identification between stars in theregion and IRAS Point Source Catalog was performed and nine newassociations were found. BVRI Johnson photometry for 24 of the matchedobjects have been carried out. Physical identity of visual and IRASsources and relationship to the Alpha Persei open cluster are discussed.
| Photoelectric photometry of carbon stars in the Vilnius system
A total of 368 observations of magnitudes and color indices of 178carbon stars in the Vilnius seven-color photometric system are given.The observations are presented in a catalog.
| Spectral indexes of cool carbon stars in the near-infrared region. II
Following the previous paper (Tanaka et al., 1990, hereafter as PaperI), near-infrared spectroscopic observations of cool carbon stars havebeen continued with the Fourier transform spectrometer and the 188 cmreflector at Okayama Astrophysical Observatory. Sixty-six spectra of 63carbon stars were analyzed. Eighteen stars were newly added to theprogram stars, and the total number of the analyzed carbon stars reached101. Three spectral indexes defined in Paper I; the color index, theCO-index, and the C2-index were measured. The same analysis was madeindependently as before, because the spectra were taken at differentphases of their variabilities and their signal-to-noise ratios were muchimproved by careful observations. General trends of the results obtainedin Paper I are confirmed.
| A general catalogue of cool carbon stars
Not Available
| IRAS low-resolution spectra of cool carbon stars. II - Stars with thin circumstellar shells. III - Stars with thick circumstellar shells
IRAS low-resolution spectra and broad-band data and near-IR photometryare analyzed for 72 carbon stars with near-IR color temperatures over2000 K. Seven stars have an almost featureless spectrum without dustemission in the LRS wavelength region. The majority of the sample starshave the 11.5 micron SiC and an unidentified 8.6 micron emission featuresuperposed on the stellar continuum. The strength of the latter featurecorrelates with the strength of the 3 micron absorption band and isprobably of molecular origin. The broad-band data exhibit a 60 micronexcess which is ascribed to a cool dust shell. The IR spectral energydistributions of those stars with thick circumstellar shells areanalyzed. The slope of the far-IR flux can best be explained by theexistence of a well-defined outer boundary of the dust shell. Thetemperature at this outer boundary implies that the present high massloss rate started 100-1000 yr ago.
| Speckle-interferometric search for multiple carbon stars.
Not Available
| A flux-limited sample of Galactic carbon stars
Published observational data (including IRAS observations) for aflux-limited sample of 215 Galactic carbon stars (CSs) selected from the2-micron sky survey of Neugebauer and Leighton (1969) are compiled inextensive tables and graphs and analyzed statistically. The sample isfound to penetrate a volume of radius 1.5 kpc, and the local CS spacedensity and surface density are calculated as log rho0 (per cu kpc) =2.0 + or - 0.4 and log N (per sq kpc) = 1.6 + or - 0.2, respectively.The total Galactic mass-return rate from these CSs is estimated as 0.013solar mass/yr, implying a time scale of 0.1-1 Myr for the CSevolutionary phase and a mass of 1.2-1.6 solar mass for the (probablyF-type) main-seqence progenitors of CSs.
| Photoelectric photometry of carbon and barium stars in the Vilnius seven-color system and their color excesses
Not Available
| IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
| Spectrophotometry of carbon stars. III - Molecular absorption bands: Quantitative analysis
The C2, CN, SiC2, and CH molecular absorption bands of 56 carbon starsare analyzed quantitatively on the basis of the spectroscopicobservations reported by Ogansian et al. (1985); the results arepresented in tables and graphs. Features noted include a separation ofearly and late stars in the C2 Swan-system red/blue index diagram, aseparation of R and N stars in the (C-12)N/(C-13)N index diagram, and acorrelation between the 4976-A Merrill-Sanford band and the 5896/5890-ANa I doublet.
| Incidence of heavy element enhancements among carbon stars
The correlation of spectral line strength with temperature subclass hasbeen examined in a survey of 40 carbon stars at a dispersion of 15 A/mm.The two goals of this search were: (1) to determine if additional coolN-type stars can be added to the list of N stars not having enhanceds-process elements; and (2) to confirm the anticorrelation of s-processenhancements with C-13 enhancement. Among the program stars one normalcarbon star was found to have no, or only minor, enhancement of heavyelements associated with the s-process. The suspicion that increasedsurface C-13 is accompanied by weak line strengths of s-process elementsis strongly confirmed.
| The Spectrophotometry of Carbon Stars - Part Two
Not Available
| The Spectrophotometry of Carbon Stars - Part One
Not Available
| Near Infrared Photometry of Carbon Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981PASJ...33..373N&db_key=AST
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