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Galactic distributions and statistics of the HD stars in the michigan spectral catalogue.
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| The Unusual Hydrocarbon Emission from the Early Carbon Star HD 100764: The Connection between Aromatics and Aliphatics
We have used the Infrared Spectrograph (IRS) on the Spitzer SpaceTelescope to obtain spectra of HD 100764, an apparently single carbonstar with a circumstellar disk. The spectrum shows emission featuresfrom polycyclic aromatic hydrocarbons (PAHs) that are shifted to longerwavelengths than normally seen, a characteristic of ``class C'' systemsin the classification scheme of Peeters et al. All seven of the knownclass C PAH sources are illuminated by radiation fields that are coolerthan those which typically excite PAH emission features. The observedwavelength shifts are consistent with hydrocarbon mixtures containingboth aromatic and aliphatic bonds. We propose that the class C PAHspectra are distinctive because the carbonaceous material has not beensubjected to a strong ultraviolet radiation field, allowing relativelyfragile aliphatic materials to survive.
| 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.
| Laboratory Simulation of 11-15 μm Spectra Associated with Polycyclic Aromatic Hydrocarbon Molecules
We have obtained 11-15 μm spectra of thin films of hydrogenatedamorphous carbon assembled from carbon nanoparticles. Well-defined,narrow features similar to the interstellar emission bands attributed topolycyclic aromatic hydrocarbons (PAHs) are observed at 11.3, 12, 12.8,13.5, and 14.2 μm. These features are reproduced in many samplesprepared under a variety of conditions, indicating that they involvecommon molecular components. We suggest that these are based on compactring structures such as coronene, C 24H12, butthat these molecules have peripheral substitutions involving additionalaromatic rings. They may also be substituted with sp- orsp2-bonded carbon chains. All bands exhibit slight energyshifts in different samples in response to changes in preparationconditions. These shifts replicate variations in wavelength and profileof the 11-15 μm bands seen in different type of emission source. Noneof the nanoparticle samples exhibit all of the 11.3, 12, 12.8, 13.5, and14.2 μm features. This implies that the interstellar bands areproduced by a limited variety of PAH structures, rather than by a singledominant species.
| Polarization Measurements of Post-Asymptotic Giant Branch Candidates and Related Stars
We have obtained UBVRI polarization measurements of 26 post-asymptoticgiant branch (post-AGB) candidates and related stars. The extremelymetal-poor post-AGB star HR 4049 has been observed several times. Inmost cases we find the objects to be intrinsically polarized. Thepolarization measurements presented in this paper indicate asymmetriccircumstellar dust shells and disks around these stars. For some objectsthe steep percent polarization λ-dependence and large degree ofpolarization suggest that scattering by circumstellar dust grains may beresponsible for the observed polarizations in the blue.
| 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
| Radiative Transfer Models of Dust Shells Around Post-AGB Stars
We present a radiative transfer analysis of circumstellar dust shellsaround the Post-AGB stars HD 179821, HD 56126, HD 101584 and early Rstar HD 100764, using the code DUSTY. Parameters like mass-loss, shellinner radius, dust temperature, outflow velocity etc., are derived forHD 179821 and HD 56126 whose observed SED could be reproduced by ourmodels.
| SiO maser survey of AGB stars in the North Galactic Cap
A SiO maser survey in the J=1-0, v=1 and 2 transitions has been made forIRAS sources in the North Galactic Cap b > 30o) with theNobeyama 45 m radio telescope. The sources were selected on the basis oftheir IRAS 12/25-μm and 25/60-μm flux ratios as likely oxygen-richAGB candidates. SiO masers were detected from 24 out of the 97 selectedsources, where 17 were new detections. The distances and heights abovethe Galactic plane are calculated. The Galactic distribution of detectedand undetected stars indicates that metallicity is likely to govern thedetection rate. The Galactocentric angular velocities of the subsampledstars are derived and their variation with the Galactic height isdiscussed. Based on observations at the Nobeyama Radio Observatory(NRO). NRO is a branch of the National Astronomical Observatory, aninter-university research institute, operated by the Ministry ofEducation, Science and Culture, Japan.
| 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.
| Orbiting Molecular Reservoirs around Evolved Red Giant Stars
We report molecular emission from the circumstellar envelopes of twocarbon-rich stars with oxygen-rich envelopes, EU And and BM Gem. We finda narrow (FWHM~5 km s^-1) CO (2-1) emission line from EU And and an evennarrower (FWHM ~ 1 km s^-1) ^13CO emission line from BM Gem. We alsoplace upper limits to the emission of HCN, SiO, SO, HCO^+, and CS fromBM Gem. We argue that the narrow CO emission lines are signatures oflong-lived reservoirs of orbiting gas and that standard models for COemission from red giant winds are not appropriate for these two stars.By including the Red Rectangle and AC Her, narrow CO emissioncharacteristic of gravitationally bound gas has been detected from fourpost-main-sequence systems, and we can begin to characterize theseapparently similar environments. Some common characteristics are thefollowing: (1) Their diameters are typically between ~100 and ~1000 AU.(2) The masses of CO are near 10^27 g. (3) Unlike the envelopes aroundmass-losing carbon stars where M_CO/M_dust~ 2, the circumstellarorbiting reservoirs often appear to have M_CO
| 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
| 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
| Infrared observation and energy distribution of silicate carbon stars.
The JHK photometric observations of all silicate carbon stars withdeclinations >-10° are presented. Combined with someobservational results in the visible and IRAS regions, the two-colordiagrams and energy distributions of the silicate carbon stars observedare discussed. Furthermore, their evolutionary characteristics are alsodiscussed.
| 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.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Carbon isotope ratio in carbon stars of the galactic halo.
We analysed CN red system (~8000Å) and C_2_ Swan system(~4700Å) to know carbon isotope ratios (^12^C/^13^C) for carbonstars in the Galactic halo, named CH stars. The isotope ratios areobtained for 6 CH stars by the curve-of-growth analysis of the isolated^12^CN and ^13^CN lines. In this analysis, we compared directly ^12^CNand ^13^CN lines of similar intensities (iso-intensity method), and theresulting ^12^C/^13^C ratios are almost independent of the modelatmosphere and its parameters. The ^13^CN lines appear to be too weak insome CH stars, for which we applied the spectral synthesis method to thestronger C_2_ Swan band, obtained ^12^C/^13^C ratios for two stars andestimated the lower limits of ^12^C/^13^C ratios for two stars. In thiscase, however, the results depend on model atmosphere and itsparameters. Results from our present and previous works show that mostof them (12 stars) distribute around ^12^C/^13^C~10 and two stars havevery high values (^12^C/^13^C>=500). The distribution of ^12^C/^13^Cratios in CH stars is different from that of the population I carbonstars as well as population II oxygen-rich giants (G~K types). The CHstars of very high ^12^C/^13^C ratios can be explained by dredge-up of^12^C due to 3α-process as in population I carbon stars (N-type).On the other hand the formation of the CH stars with low ^12^C/^13^Cratios requires the large supply of ^12^C followed by a process ofdecreasing ^12^C/^13^C ratio.
| 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
| 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.
| Stellar Evolution and Late Type Stars
The M, S and C stars may be placed in an evolutionary sequence on thebasis of direct observation of the spectroscopic transitions on the AGBof rich intermediate-age clusters in the Magellanic Clouds, but some Sand C stars cannot be accounted for in this way. The S stars inωCentauri owe their peculiarity to a primordial enrichment in s-processelements. The J-type (13C-rich) carbon stars originate in adifferent way to the ordinary cool N-type carbon stars. Some of themhave silicate-rich circumstellar dust, contrary to expectation. Some ofthe carbon-rich RV Tauri stars also have silicate-rich dust and in bothcases it may be organised in a disc. Observational evidence for gas anddust ejection by ordinary N-type carbon stars has been found and may beinferred for some RV Tauri stars.
| The dust disk around the vega-excess star SAO 26804
We present multiwaveband observations of the K2 Vega-excess star SAO26804 (= HD 233517). These include James Clerk Maxwell Telescopemillimeter-wave photometry, plus spectra in the 8-13 microns and 18-24microns atmospheric windows, an image at a wavelength of 10 micronsthrough a broadband N filter and near-IR (JHKLL'M) photometry all takenat the United Kingdom Infrared Telescope. The source is resolved at 10microns, and we can confirm with these observations that the IR excessseen in IRAS observations of this source is associated with the opticalstar. The image is consistent with the dust being confined to a diskwith Full Width at Half Maximum (FWHM) 1.5 sec on the major axis, withan inclination angle of less than 30 deg away from edge-on. Thisrepresents the first confirmation that the dust in a Vega-excess starother than beta Pic is confined to a disk geometry. We present models ofthe source which show that many of the properties of the disk and thedust in it are similar to those which we have previously derived for thedisk around SAO 179815, but that there are some very small grains in thedisk around the star which give around SAO 179815, but that there aresome very small grains in the disk around the star which give rise to avery prominent and narrow silicate dust feature at 9.7 microns and toso-called unidentified infrared bands in the 10 micron region. Thelarger grains are composed of a mixture of amorphous carbon and silicatewith an abundance ratio consistent with an interstellar origin. Thetotal mass of dust in the disk is 3.0 x 10-7 solar mass.Finally, our model suggests that there may be a substantial UV and/orsoft X-ray flux from SAO 26804, consistent with it being a very youngand rather active star.
| Search for T Tauri Stars Based on the IRAS Point Source Catalog. II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2146T&db_key=AST
| Red giants with unusual dust shells. II. The dusty R star HD 100764.
Abstract image available at:http://adsabs.harvard.edu/abs/1994MNRAS.271..300S
| More H_2_O maser in J-type carbon stars
The detection of five new H_2_O masers in J-type carbon stars isreported, confirming the suggestion made earlier that they have anoxygen-rich environment. This increases the sample of peculiar carbonstars of this type to 13. The high maser detection rate suggests thatperhaps all J-type carbon stars with IRAS flux ratios S_25_/S_12_ >0.45 have oxygen-rich environment. Two of the new stars show largeradial velocities, stimulating the suggestion that these carbon starsbelong to the metal-weak halo population.
| Revised MK spectral classification of the red carbon stars
The spectral classification of the red carbon stars has been broughtinto the revised MK system by combining some of the features of the oldR, N, and C classifications, as modified by Yamashita, and addingnumerical abundance indices. The new types are intended to (1) definethe population to which the star belongs, (2) allow quick interpolationbetween the detailed atmospheric analyses of individual stars, and (3)indicate the differences between carbon stars in different parts of ourgalaxy, and in other galaxies. It is the flexibility of the notation,allowing the incorporation of improved criteria, that should make thenew system useful.
| 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.
| A model of the 2-35 micron Point Source Infrared Sky
The Point Source Infrared Sky Model of Wainscoat et al. (1992) isextended to make predictions for any filter lying wholly within therange 2.0 to 35.0 micron. The development of a library of complete 2-35micron low-resolution spectra that represent the 87 categories ofGalactic object and four types of extragalactic source implicit in theModel supports this extension. This library is based upon the 'spectraltemplate' technique whereby existing spectral fragments for individualsources (from ground-based, airborne, and satellite-borne instruments)are combined into complete spectra. Templates provide a natural way torepresent the complete spectral energy distributions of celestialsources for which only infrared photometry and/or partial spectroscopyare available. Consequently, templates bear upon the important generalproblem of establishing midinfrared calibration sources. The new modelis validated by comparison with broadband K source counts.
| Candidates for carbon stars with silicate features
Characteristics of color distributions in IRAS bands of carbon stars,which are well-known samples with silicate features, are examined. Somecandidates of carbon stars with silicate features are presented.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
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