Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Near-infrared photometry of carbon stars
Near-infrared, JHKL, photometry of 239 Galactic C-rich variable stars ispresented and discussed. From these and published data, the stars wereclassified as Mira or non-Mira variables, and amplitudes and pulsationperiods, ranging from 222 to 948 d for the Miras, were determined formost of them. A comparison of the colour and period relations with thoseof similar stars in the Large Magellanic Cloud indicates minordifferences, which may be the consequence of sample selection effects.Apparent bolometric magnitudes were determined by combining the meanJHKL fluxes with mid-infrared photometry from IRAS and MSX. Then, usingthe Mira period luminosity relation to set the absolute magnitudes,distances were determined - to greater accuracy than has hitherto beenpossible for this type of star. Bolometric corrections to the Kmagnitude were calculated and prescriptions derived for calculatingthese from various colours. Mass-loss rates were also calculated andcompared to values in the literature.Approximately one-third of the C-rich Miras and an unknown fraction ofthe non-Miras exhibit apparently random obscuration events that arereminiscent of the phenomena exhibited by the hydrogen-deficient RCoronae Borealis stars. The underlying cause of this is unclear, but itmay be that mass loss, and consequently dust formation, is very easilytriggered from these very extended atmospheres.Based on observations made at the South African AstronomicalObservatory.E-mail: paw@saao.ac.za
| Infrared photometry and evolution of mass-losing AGB stars. I. Carbon stars revisited
As part of a reanalysis of galactic Asymptotic Giant Branch (AGB) starsat infrared (IR) wavelengths, we discuss a sample (357) of carbon starsfor which mass loss rates, near-IR photometry and distance estimatesexist. For 252 sources we collected mid-IR fluxes from the MSX (6C) andthe ISO-SWS catalogues. Most stars have spectral energy distributions upto 21 μm, and some (1/3) up to 45 μm. This wide wavelengthcoverage allows us to obtain reliable bolometric magnitudes. Theproperties of our sample are discussed with emphasis on ~70 stars withastrometric distances. We show that mid-IR fluxes are crucial toestimate the magnitude of stars with dusty envelopes. We construct HRdiagrams and show that the luminosities agree fairly well with modelpredictions based on the Schwarzschild's criterion, contrary to what iswidely argued in the literature. A problem with the brightness of Cstars does not appear to exist. From the relative number of Mira andSemiregular C-variables, we argue that the switch between these classesis unlikely to be connected to thermal pulses. The relevance of the twopopulations varies with the evolution, with Miras dominating the finalstages. We also analyze mass loss rates, which increase for increasingluminosity, but with a spread that probably results from a dependence ona number of parameters (like e.g. different stellar masses and differentmechanisms powering stellar winds). Instead, mass loss rates are wellmonitored by IR colours, especially if extended to 20 μm and beyond,where AGB envelopes behave like black bodies. From these colours theevolutionary status of various classes of C stars is discussed.
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| The mass loss of C-rich giants
The mass loss rates, expansion velocities and dust-to-gas density ratiosfrom millimetric observations of 119 carbon-rich giants are compared, asfunctions of stellar parameters, to the predictions of recenthydrodynamical models. Distances and luminosities previously estimatedfrom HIPPARCOS data, masses from pulsations and C/O abundance ratiosfrom spectroscopy, and effective temperatures from a new homogeneousscale, are used. Predicted and observed mass loss rates agree fairlywell, as functions of effective temperature. The signature of the massrange M≤4 Mȯ of most carbon-rich AGB stars is seenas a flat portion in the diagram of mass loss rate vs. effectivetemperature. It is flanked by two regions of mass loss rates increasingwith decreasing effective temperature at nearly constant stellar mass.Four stars with detached shells, i.e. episodic strong mass loss, andfive cool infrared carbon-rich stars with optically-thick dust shells,have mass loss rates much larger than predicted values. The latter(including CW Leo) could be stars of smaller masses (M≃ 1.5-2.5Mȯ) while M≃ 4 Mȯ is indicated formost of the coolest objects. Among the carbon stars with detachedshells, R Scl returned to a predicted level (16 times lower) accordingto recent measurements of the central source. The observed expansionvelocities are in agreement with the predicted velocities at infinity ina diagram of velocities vs. effective temperature, provided the carbonto oxygen abundance ratio is 1≤ɛ C/ɛO≤2, i.e. the range deduced from spectra and modelatmospheres of those cool variables. Five stars with detached shellsdisplay expansion velocities about twice that predicted at theireffective temperature. Miras and non-Miras do populate the same locus inboth diagrams at the present accuracy. The predicted dust-to-gas densityratios are however about 2.2 times smaller than the values estimatedfrom observations. Recent drift models can contribute to minimize thediscrepancy since they include more dust. Simple approximate formulaeare proposed.This research has made use of the Simbad database operated at CDS.Partially based on data from the ESA HIPPARCOS astrometry satellite.Table 3 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/429/235
| 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
| Millimetre observations of infrared carbon stars. II. Mass loss rates and expansion velocities
Dust- and gas mass loss rates and distances are determined for a sampleof about 330 infra-red carbon stars that probe a distance up to about5.5 kpc. The dependence of the dust- and gas mass loss rates, and theexpansion velocity upon galactic longitude (l) are studied. It is foundthat the expansion velocity significantly depends on l, but that theabsolute bolometric magnitude, the dust mass loss rate and thegas-to-dust ratio depend on l marginally, if at all, and the gas massloss rate does not depend on l. Beyond the solar circle, the expansionvelocity (as well as the luminosity, dust-to-gas ratio, dust mass lossrate) is lower than inside the solar circle, as expected from theoverall gradient in metallicity content of the Galaxy. Combining theaverage expansion velocity inside and beyond the solar circle with thetheoretically predicted relation between expansion velocity andgas-to-dust ratio, we find that the metallicity gradient in the solarneighbourhood is about -0.034 dex/kpc, well within the quoted range ofvalues in the literature.
| Millimetre observations of infrared carbon stars. I. The data
Millimetre observations of IRAS selected red carbon stars are presented.About 260 stars have been observed with SEST and IRAM in the CO (1-0)and CO (2-1) lines and partially in HCN (1-0) and SiO (3-2). An overalldetection rate, in at least one line, of about 80% is achieved. Thesurvey represents the second largest survey for AGB stars, and thelargest ever for carbon stars. Two new detections in SiO (3-2) in carbonstars are reported. When available, the SiO/HCN and HCN/CO (1-0) lineratios are consistent with the ratios expected for carbon stars. Basedon observations collected at the European Southern Observatory, LaSilla, Chile within program ESO 60.E-0103, 62.L-0128, 64.L-0012 and66.D-0027. Also based on observations with the IRAM telescope, Granada,Spain under programs 98-97, 141-97 and 010-99. The complete Fig. 1 isonly available in electronic form at http://www.edpsciences.org. Thecomplete Table 3 is 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/390/501
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe 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/386/492, and from theauthors on CD-Rom.
| 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
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| 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.
| Hipparcos parallaxes for Mira-like long-period variables
This paper concerns the calibration of the K period-luminosity relationfor Mira variables using Hipparcos parallaxes. K magnitudes areavailable for 255 Mira-like variables which were observed by Hipparcos.Period-luminosity zero-points are evaluated for various subgroups ofdata. The best solution for oxygen-rich Miras, which uses 180 stars,omitting the short-period red group (which had different kinematics fromthe short-period blue stars) and the low-amplitude variables, provides azero-point of σ2σ2π +(0.4605)2π2PL(K)σ2K + σ2PL(K),0.84+/-0.14mag, which implies a distance modulus for the LargeMagellanic Cloud of σK = 0.3ΔK√N,18.64+/-0.14mag, or perhaps slightly greater if a metallicity correctionis required, in good agreement with the value derived from Cepheids. Thezero-point of the period-luminosity relation for carbon stars is brieflydiscussed. Linear diameters are derived for red variables with measuredangular diameters and parallaxes, and are used to examine thelong-standing question of the pulsation mode(s) of these stars. Evidenceis presented to suggest that most of them are pulsating in the same modeand, if published model atmospheres are correct, this is probably thefirst overtone. Some discussion is given of sequences in theperiod-luminosity and period-colour diagrams and their bearing on thepulsation mode problem.
| Distance Determination of Mass-Losing Stars
Based on the Principal Component Analysis on IRAS colors and the radiodata, the distances to 183 mass-losing red giant stars were determinedusing the radial velocity and Oort's galactic rotation model for azero-point calibration in the distance modulus. Also, based on therequirement of higher accuracy of the distance determination, themass-losing red giant stars were divided into two groups by means of thefirst-principal component representing an intrinsic photometric propertyof the expanding shell; then, the distances were estimated to be log{d(kpc)}=0.458 p_2+0.09+/-0.13 for group 1 and log {d(kpc)}=0.325p_2+0.45+/-0.15 for group 2, where p_2 is the principal componentcorresponding to the distance, as obtained from the IRAS flux, which wasassumed to be inversely proportional to the square of the distance.Thus,these two groups differ from each other not only by theirphotometric properties, but also by their average distances, by a factorof about 2. Systematic differences exist between the two groups in theirpopulation characteristics and in their evolutionary stages.
| 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.
| The carbon-rich dust sequence - Infrared spectral classification of carbon stars
We have developed a classification system for the infrared spectralemission from carbon stars using a sample of 96 bright carbon-richvariables associated with the asymptotic giant branch. In addition tothe stellar contribution, most spectra include the 11.2 micron emissionfeature from SiC and either a smooth, cool continuum from amorphouscarbon or a secondary emission feature at 9.0 microns. We haveidentified a carbon-rich dust sequence along which the amorphous carboncomponent grows while the 9.0 micron feature declines in strength. Alongthis spectral sequence, the proportion of Mira variables increases, asdoes the period of variability, the mass-loss rate, and the thickness ofthe circumstellar shell. Thus the carbon-rich dust sequence appears tobe an evolutionary sequence. One class of spectra shows a particularlystrong 9.0 micron feature, enhanced C/O ratio, and several other unusualproperties that suggest a different sequence, perhaps related to Jstars.
| 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.
| Irregular variables of type Lb. New JHKL'M-photometry for 160 stars.
This paper presents new near infrared observations of 160 Irregularvariables of type Lb in the JHKL'M filter bands. These measurements aresupplemented by data for additional 56 stars taken from the literature.In total 220 datasets are available because of some multipleobservations. From our sample, 216 stars have near infrared (NIR)photometry now. Our sample of visually bright Lb-variables displays verysimilar infrared properties when compared with SRa- and SRb-variables.Derived from NIR-two colour diagrams the oxygen-rich Lbs seem to haveintermediate atmospheric conditions between Miras and normal giants.There may be a sligthly larger "contamination" with non AGB-giants thanin the case of the semiregulars. Using only our IR-colours the S- andthe Carbon-stars among the Lbs again are undistinguishable fromSR-variables of the same chemistry.
| 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
| The radio properties of high-redshift quasars. I - Dual-frequency observations of 79 steep-spectrum quasars at Z over 1.5
We have made sensitive VLA observations of virtually all knownhigh-redshift radio-loud QSOs with extended radio morphologies. Theresulting images have angular resolutions of typically 0.4 and 0.15arcsec and are compiled here. This compilation of maps will permit theextraction of numerous radio source parameters, constituting a data basefor comprehensive statistical analyses to be explored in subsequentpapers. The data base is particularly useful for statistical studies.The key characteristics of the sample are the narrow redshift range, thenarrow distribution in linear resolutions of the maps, the narrowdistribution of map sensitivity to emitting regions of standard physicalcharacteristics, and the relatively narrow range of source luminosities.As a result of these properties, the sample enjoys relative freedom fromthe effects of parameter correlations with redshift and luminosity. Abrief discussion of the sample characteristics and some elaboration ofthe particular advantages of this sample are presented. Some cleartrends in the data are discussed briefly.
| Circumstellar shells resolved in the IRAS survey data. I - Data processing procedure, results, and confidence tests
We have examined the IRAS 60 and 100 micron survey data covering 512evolved stars and young planetary nebulae for evidence of spatiallyresolved structure. A simple model, consisting of a central unresolvedsource surrounded by a resolved isothermal shell, was fitted to the datafor each star. Seventy-six stars were found to be resolved in the 60micron data. Tests have been performed to verify that the extendedstructure seen is not an artifact of the data-processing algorithm.
| 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.
| 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.
| Carbon star envelopes - Near-IR photometry, mass loss and evolutionary status of a sample of IRAS stars
This paper presents results of JHLKM photometry data analysis of 249southern 'IRAS-discovered' stars, which exhibit an emission feature at11.3 microns in their low-resolution spectra (class 4n stars). Themethod of Epchtein et al. (1987) is used to separate oxygen-rich andcarbon-rich stars on the basis of their sole NIR and IRAS broad-bandfluxes. It is shown that NIR data are necessary to calculate the totalIR energy received from IRAS stars and such fundamental parameters asindividual mass loss rates. An evolutionary model is developed to matchthe sequence of stars in color diagrams. It is suggested that thesequence of increasing optical depths might not be an evolutionarysequence, but would rather reflect the termination of a process in whichthe near-IR index increases very quickly at the beginning and isstrongly dependent on the mass loss rate.
| A general catalogue of cool carbon stars
Not Available
| Spectrophotometric investigation of carbon stars
Not Available
| AGK3 Stars with Spuriously Large Proper Motions
Not Available
| The absolute spectrophotometry of carbon stars. VI. Abundance of carbon in the atmospheres.
Not Available
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Gemini |
| Ascensió Recta: | 06h34m23.92s |
| Declinació: | +16°04'30.3" |
| Magnitud Aparent: | 8.826 |
| Distancia: | 323.625 parsecs |
| Moviment propi RA: | -2.9 |
| Moviment propi Dec: | -6.5 |
| B-T magnitude: | 13.866 |
| V-T magnitude: | 9.243 |
Catàlegs i designacions:
|
