Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
NSCC—A New Scheme of Classification of C-Rich Stars Devised from Optical and Infrared Observations
A new classification system for carbon-rich stars is presented based onan analysis of 51 asymptotic giant branch carbon stars through the mostrelevant classifying indices available. The extension incorporated,which also represents the major advantage of this new system, is thecombination of the usual optical indices that describe the photospheresof the objects, with new infrared ones, which allow an interpretation ofthe circumstellar environment of the carbon-rich stars. This new systemis presented with the usual spectral subclasses and C2-, j-,MS-, and temperature indices, and also with the new SiC- (SiC/C.A.abundance estimation) and ?- (opacity) indices. The values for theinfrared indices were carried out through a Monte Carlo simulation ofthe radiative transfer in the circumstellar envelopes of the stars. Thefull set of indices, when applied to our sample, resulted in a moreefficient system of classification, since an examination in a widespectral range allows us to obtain a complete scenario for carbon stars.
| Infrared Study of J-Type Carbon Stars Based on Infrared Astronomical Satellite, Two Micron All Sky Survey, and Infrared Space Observatory Data
We collected 113 J-type carbon stars from the published literature.Observations from 2MASS, IRAS, and ISO show that, except for silicatecarbon stars in the J-type carbon star domain, the infrared propertiesof the other J-type carbon stars are quite similar to those of ordinarycarbon stars. The above results imply that the chemical peculiarity ofenhanced 13C for J-type carbon stars is not reflected in theinfrared region. In addition, the possible evolutionary scenario andbinarity for J-type carbon stars are also discussed.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| 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
| 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.
| Quantitative analysis of carbon isotopic ratios in carbon stars. III. 26 J-type carbon stars including 5 silicate carbon stars
We present the result of a quantitative analysis of (12C/({13)) C}ratios in 26 J-type carbon stars. The (12C/({13)) C} ratios aredetermined from lines of the CN red system around 8000 Angstroms, usingthe iso-intensity method and line-blanketed model atmospheres. Theaverage of (12C/({13)) C}\ ratios in the 26 stars is 4.7 +/- 2.8(standard deviation). All the stars studied, except for two stars, have(12C/({13)) C}\ ratios smaller than 10. (12C/({13)) C}\ ratios as low as1 ~ 2, which are lower than the value at the equilibrium of theCN-cycle, are found for a significant fraction of our sample, suggestingthe operation of non-equilibrium nuclear processes. For several starspreviously analyzed by other authors, our result shows fair agreement.The serious disagreement of (12C/({13)) C}\ ratios, which we reportedfor N-type carbon stars in our preceding paper, is not found for J-typecarbon stars. Five silicate carbon stars in our sample show no peculiar(12C/({13)) C} ratios among the stars studied in the present work. Thisresult implies that the mechanism responsible for low (12C/({13)) C}\ratios in silicate carbon stars might be the same with that operating inother J-type carbon stars. In other words, (12C/({13)) C}\ ratios insilicate carbon stars have turned out to give few clues to identify themechanism responsible for their formation.
| Dust extinction and intrinsic SEDs of carbon-rich stars. III. The Miras, CS, and SC stars
The present work is an extension of a recent study by Knapik &Bergeat (\cite{knapik97}), and Bergeat et al. (\cite{berge98b})henceforth called Papers I and II, respectively. The spectral energydistributions (SEDs) of about 440 carbon-rich stars and the interstellarextinction observed on their line of sights were analysed. The methodsoriginally developed for Semi-Regular (SR) and Irregular (L) variables(Paper I: our groups CV1 to CV6) were then extended (Paper II) to thehot carbon (HC) stars (our groups HC0 to HC5) and related objects (RCB,BaII and HdC stars). Shortly, this is a kind of a pair method making usesimultaneously of the whole SED from UV to IR. Our approach is appliedhere to the galactic cool carbon-rich variables which were notconsidered in Paper I, namely the carbon Miras and very cool non-Miras,and the CS and SC variables. The carbon Miras with infrared silicateemission are also studied. The photometric CV1 to CV6 classificationscheme of paper I is implemented, and we add here a later CV7-group anda specific SCV-group which corresponds to spectroscopic SC stars. Acontinuous S-SC-CS-C sequence is clearly supported by our results. Thecarbon stars with IR silicate emission included in our study do havecarbon-rich SEDs of the three consecutive groups HC5, CV1 and CV2. Theystand among the relatively hot carbon variables, in the 3600-3000 Krange in effective temperature. The carbon Miras are satisfactorilydescribed in this enlarged scheme. No specific extension is requiredsince non-Miras are also found in the CV7 and SCV-groups. The derivedgroup is however frequently phase-dependent in these large amplitudevariables. Additional selective extinction of circumstellar (CS) originis observed in variable amounts. The mean extinction law for theinterstellar diffuse medium as tabulated by Mathis (\cite{mathis}) isshown to be relevant. It applies to both interstellar and circumstellarextinction with a possible CS neutral extinction in addition which wouldremain undetected here. The corresponding colour excess E(B-V) is largerat minimum light or intermediate phases than what it is at maximum light(where it can amount to zero). It is associated to large IR excessesattributed to the emission from CS dust. Long-term variations onthousands of days may be interpreted in terms of varying CS dust opacityon the line of sight. The dust influence is discussed. It is shown thatscattering, if substantial on the line of sight in the observing lobe,has to be essentially wavelength-independent, i.e. due to large neutralscatterers, especially in high opacity objects like IRC +10216. Finally,with the HC0 to HC5 classification of HC stars (Paper II), we obtain afourteen groups sequence (HC0 to HC5 and then CV1 to CV7 from theearlier one to the latest one, and SCV for SC stars apart). The numberof studied stars amounts now to about 600 that is about 40 stars pergroup on the average when the oxygen-type SEDs are subtracted. Theeffective temperature calibration of this classification scheme iscurrently in preparation. This research has made use of the Simbaddatabase operated at CDS, Strasbourg, France.}\fnmsep\thanks{Partiallybased on data from the ESA HIPPARCOS astrometrysatellite}\fnmsep\thanks{Table~5 is only available in electronic form atthe CDS via anonymous ftp 130.79.128.5
| 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.
| 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.
| 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.
| Photoelectric photometry of carbon, barium and related stars in the Vilnius system and their colour excesses. II
The paper contains a catalogue of 63 galactic field carbon, barium, andrelated stars. The catalogue presents the results of photoelectricphotometry in the Vilnius system, together with the data compiled fromthe literature. Several methods are used to estimate color excessesE(B-V) of the stars.
| The 77-81 intermediate-band photometric system
The 77-81 intermediate-band photometric color system for the study oflate-type stars is defined. The passbands are centered on a region ofTiO absorption at 7750 A (77) and on a region of CN absorption at 8100 A(81). Good agreement is found between measurements made on the 77-81system with different detectors. The 77-81 color is well correlated withM type and reasonably correlated with carbon-richness class. The 77-81,V-I color-color diagram clearly distinguishes M and C types from otherstars. It is also shown that the 77-81 color may be used to measure TiOband strength.
| A general catalogue of cool carbon stars
Not Available
| UBV photoelectric catalogue (1986). II - Analysis
The UBV photoelectric data of the stars presenting several entries inthe 1986 edition of the UBV catalog have been systematicallyintercompared, and this paper presents a discussion of the stars forwhich discrepancies larger than 0.2 mag were found. Thirty-six probablyvariable stars have been detected, among which 18 are Be stars. Sixtyfurther stars present differences in the V magnitude larger than 0.2mag. Sixteen stars already appear in the NSV catalog. Although manyproblems are probably due to poor observations, new (eclipsing) variablestars may be found in this sample. Complete disagreement is foundbetween the values published from two independent sources in 34 cases. Afirst analysis of the quality of the UBV data shows that 65 percent ofthe differences in the V magnitude and in U-B color, for respectively11,500 and 7200 stars with two sources of data, are smaller than 0.04.The scatter on the B-V index appears to be smaller, since the samepercentage reaches 79 percent.
| UBV Photoelectric Photometry Catalogue (1986). III Errors and Problems on DM and HD Stars
Not Available
| CH stars as galaxy halo tracers
A spectroscopic survey of high-latitude carbon stars shows that many ofthese stars are CH stars with characteristically high space velocities.Some newly determined CH stars and others compiled from the literatureare employed to determine the local space density and kinematics ofthese stars. For the local space density, the surprisingly high value ofrho = 5.6 x 10 to the -9th/cu pc is obtained for M(V) ranging from -0.25to -2.2. The main result of the present study is that the velocitydispersion perpendicular to the galactic plane sigma(W) is alwaysgreater than approximately 114 km/s, irrespective of how the sample ofknown CH stars and CH star candidates is subdivided.
| Photometry and Radial Velocities of Southern Carbon Stars
Not Available
| Kinematic properties of the carbon stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..364D&db_key=AST
| A general catalogue of cool carbon stars
Not Available
| Some Intrinsic Properties of Carbon Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJ...167..521R&db_key=AST
| Multicolor Photometry of Carbon Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965ApJ...141..161M&db_key=AST
| Low Dispersion Spectra of Some Carbon Stars
Abstract image available at:http://adsabs.harvard.edu/abs/1959PASJ...11..257K
| The magnitudes, colors and motions of stars of spectral class R.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..477V&db_key=AST
| Radial Velocities of 283 Stars of Spectral Classes R and N.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1944ApJ....99..145S&db_key=AST
| Not Available
Not Available
| Radial Velocities of Stars of Spectral Class R
Not Available
| Stars having peculiar spectra.
Not Available
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Terazi |
| Sað Açýklýk: | 15h04m00.51s |
| Yükselim: | -02°51'05.2" |
| Görünürdeki Parlaklýk: | 10.097 |
| özdevim Sað Açýklýk: | -3.3 |
| özdevim Yükselim: | -0.4 |
| B-T magnitude: | 13.582 |
| V-T magnitude: | 10.385 |
Kataloglar ve belirtme:
|
