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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
| Reprocessing the Hipparcos data for evolved giant stars II. Absolute magnitudes for the R-type carbon stars
The Hipparcos Intermediate Astrometric Data for carbon stars have beenreprocessed using an algorithm which provides an objective criterion forrejecting anomalous data points and constrains the parallax to bepositive. New parallax solutions have been derived for 317 cool carbonstars, mostly of types R and N. In this paper we discuss the results forthe R stars. The most important result is that the early R stars (i.e.,R0 - R3) have absolute magnitudes and V-K colors locating them among redclump giants in the Hertzsprung-Russell diagram. The average absolutemagnitude MK for early R-type stars (with V - K < 4) hasbeen derived from a Monte-Carlo simulation implicitly incorporating allpossible biases. It appears that the simulated magnitude distributionfor a population with a true Gaussian distribution of mean MK= -2.0 and intrinsic standard deviation 1.0 mag provides a satisfactorymatch to the observed distribution. These values are consistent with theaverage absolute magnitude MK = -1.6 for clump red giants inthe solar neighborhood (Alves 2000). Further, early R-type stars arenon-variable, and their infrared photometric properties show that theyare not undergoing mass loss, properties similar to those of the redclump giants. Stars with subtypes R4 - R9 tend to be cooler and havesimilar luminosity to the N-type carbon stars, as confirmed by theirposition in the (J-H, H-K) color-color diagram. The sample of earlyR-type stars selected from the Hipparcos Catalogue appears to beapproximately complete to magnitude K0 ~ 7, translating intoa completeness distance of 600 pc if all R stars had MK= -2(400 pc if MK= -1). With about 30 early R-type stars in thatvolume, they comprise about 0.04% (0.14% for MK= -1) of thered clump stars in the solar neighborhood. Identification with the redclump locates these stars at the helium core burning stage of stellarevolution, while the N stars are on the asymptotic giant branch, wherehelium shell burning occurs. The present analysis suggests that for asmall fraction of the helium core burning stars (far lower than thefraction of helium shell-burning stars), carbon produced in the interioris mixed to the atmosphere in sufficient quantities to form a carbonstar. Based on observations from the Hipparcos astrometric satelliteoperated by the European Space Agency (ESA 1997).
| 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.
| Dust extinction and intrinsic SEDs of carbon-rich stars. II. The hot carbon stars
The present work is an extension of a recent study by Knapik &Bergeat (\cite{knapik}, henceforth called Paper I) of the spectralenergy distributions (SEDs) of about 300 cool carbon-rich variables andof the interstellar extinction observed on their line of sights. Themethods were originally developed for Semi-Regular (SR) and Irregular(L)-variables. 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 carbon-rich giants with bluer SEDs, namely the hotcarbon (HC) stars, including many ``constant'' stars and a minority ofvariables: AC Her a RV Tau star, the R Coronae Borealis (RCB) stars andothers. Some HdC (i.e. carbon-rich hydrogen deficient stars) and Ba IIstars are also considered. The total number of studied HC stars amountsto about 140. With few exceptions, the colour excesses for interstellarextinction are found in good agreement with the field values from mapspublished in the literature, taking into account the approximatedistances to our stars from HIPPARCOS data (\cite{esa}, henceforthcalled ESA) or binarity. We propose a classification scheme with sixphotometric groups (or boxes: HC0 to HC5) from the bluest to the reddestSEDs. Oxygen-rich SEDs earlier than HC0, are attributed to the hotteststars (AC Her, most RCB-variables and a few others). Previous findingsare confirmed of a junction between oxygen-rich and carbon-rich SEDs atspectral type G. The latest (HC5) group is immediately close to theearliest one in Paper I, namely CV1. The sequence of groups then goesregularly from HC0 to CV6. Substantial infrared excesses with respect toour solutions are found in HD 100764 a HC1 carbon star, AC Her a G0g RVTau star, and the RCB stars classified in either HC or oxygen-groups.The colour excesses at maximum light can usually be attributed tointerstellar reddening, with neutral circumstellar (CS) reddening (largegrains) or no CS extinction at all on the line of sight (non sphericalgeometry) as possible explanations. The latter model (disc or patchydistribution through successive puffs) is favoured. Two RCB variablesfor which we exploit SEDs on a rising branch (V CrA) or minimum light(RS Tel), show CS laws, respectively a selective extinction compatiblewith small grains and an extinction partly neutral indicative of largegrains on the line of sight. 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{Tables~3 and 4 are only available in electronicform at the CDS via anonymous ftp 130.79.128.5
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| A general catalogue of cool carbon stars
Not Available
| Recognition and classification of strong-CN giants
Fifty of the stars designated as super-metal-rich by Spinrad and Taylor(1969) are classified here on the Revised MK System. Positive CN indicesare assigned in recognition of the characteristic excesses of carbon andnitrogen in their atmospheres, as compared to normal Population I stars.For only a few of the stars, an abnormal strength of the iron lines orof Ca 4226 A is so noticeable that they need to be distinguished bypositive indices for these metals.
| Photoelectric photometry of carbon and barium stars in the Vilnius seven-color system and their color excesses
Not Available
| Infrared flux excesses of the warm carbon stars
Infrared photometry of 31 stars having enhanced atmospheric carbonabundances (types R, CH, Ba II) has been obtained to test for thepresence of circumstellar dust emission reported by others. Supplementedby published ground-based and IRAS photometry, energy distributionsspanning the range 0.33-100 microns have been examined. No new excesseslarge enough to be ascribed to the presence of dust having T = 1000-1500K have been found in this survey of warm carbon stars. Some marginalevidence exists for the presence of warm (T = 300 K) dust associatedwith two stars. One star, BD + 17 deg 3325, earlier reported to haveexcess emission at 3.5 microns, has been shown to have no substantailflux excess at wavelengths as long as 4.6 microns, and perhaps 10.2microns. The distinctive colors of carbon-rich stars are found to becaused by increased line blanketing relative to the ordinary giants, andnot due to circumstellar dust emission.
| Bolometric luminosities and infrared properties of carbon stars in the Magellanic Clouds and the Galaxy
Infrared photometry of a selection of the Blanco et al. (1980) completesample of C stars in the LMC and SMC, and of a sample of field C starsin the Galaxy, shows that the basic trends of the infrared colors andindices for C stars in the Galaxy and Magellanic clouds are similar butnot identical. The photometry was used with the bolometric correctionsof Frogel et al. (1980) to derive a bolometric luminosity function forthe BMB sample, which was then compared with evolutionary calculationsof double shell burning stars undergoing He shell flashes. It is foundthat: (1) the shape of the luminosity distribution in I or BMB is thatof the bolometric luminosity function; (2) none of the availabletheoretical models can reproduce the SMC and LMC luminosity distributionfor C stars, as M(bol) is predicted to be too bright; and (3) theobserved luminosity function is approximately Gaussian, with a FWHM ofabout 0.8 mag in both the SMC and LMC.
| Photometry and Radial Velocities of Southern Carbon Stars
Not Available
| A general catalogue of cool carbon stars
Not Available
| 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
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| Sað Açýklýk: | 05h42m54.75s |
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