DSS Images Other Images
|The Indo-US Library of Coudé Feed Stellar Spectra|
We have obtained spectra for 1273 stars using the 0.9 m coudéfeed telescope at Kitt Peak National Observatory. This telescope feedsthe coudé spectrograph of the 2.1 m telescope. The spectra havebeen obtained with the no. 5 camera of the coudé spectrograph anda Loral 3K×1K CCD. Two gratings have been used to provide spectralcoverage from 3460 to 9464 Å, at a resolution of ~1 Å FWHMand at an original dispersion of 0.44 Å pixel-1. For885 stars we have complete spectra over the entire 3460 to 9464 Åwavelength region (neglecting small gaps of less than 50 Å), andpartial spectral coverage for the remaining stars. The 1273 stars havebeen selected to provide broad coverage of the atmospheric parametersTeff, logg, and [Fe/H], as well as spectral type. The goal ofthe project is to provide a comprehensive library of stellar spectra foruse in the automated classification of stellar and galaxy spectra and ingalaxy population synthesis. In this paper we discuss thecharacteristics of the spectral library, viz., details of theobservations, data reduction procedures, and selection of stars. We alsopresent a few illustrations of the quality and information available inthe spectra. The first version of the complete spectral library is nowpublicly available from the National Optical Astronomy Observatory(NOAO) via ftp and http.
|Luminosity and Temperature from Near-Infrared Spectra of Late-Type Giant Stars|
We present moderate resolution (lambda / Delta lambda ~ 1380 and lambda/ Delta lambda ~ 4830) spectra of 43 K0 to M6 III stars covering 2.19 -2.34 mu m and measure equivalent widths of the strongest absorptionfeatures - Na I, Ca I, and (12) CO(2,0) - present on the spectra. Thehigh resolution Wallace & Hinkle (1996) spectral atlas shows thatour moderate resolution measurements of the atomic features havesignificant contributions from other species, such as Sc, S, Fe, Ti, Si,and V. We also find that our measured equivalent widths are affected byCN absorption present in the continuum bands. In spite of this, theequivalent widths of Na I and Ca I features at moderate resolution stillshow a strong dependence on effective temperature. The CO equivalentwidth at moderate resolution is less affected by other lines andcontinuum placement than the atomic features, because of its relativelygreater strength. We compare our data to similar data taken forlate-type dwarf stars (Ali et al. 1995) and find that a two dimensionalspectral classification can be constructed based on the near-IR spectra.The quantity log[EW(CO)/(EW(Na)+EW(Ca))] is a strong luminosityindicator independent of effective temperature, while the equivalentwidth of (12) CO(2,0) has a well-defined dependence on effectivetemperature for a given luminosity. This two dimensional spectralclassification is ideal for cool stars obscured by dust in, for example,the central part of the Galactic bulge and regions of star formation.
|Giants with infrared excess.|
We have correlated optical and infrared catalogs in order to extract alarge sample of luminosity class III stars with known infrared fluxdensities. For a non-negligible fraction of G and K giants, afar-infrared excess emission was found, starting beyond 25μm. Anexplanation in terms of present-day mass loss thus becomes unlikely,since the dust should then be warmer and the excess emission less far inthe infrared. We believe that the far-infrared excesses of theseobjects, most likely first-ascent giants, are related to the Vegaphenomenon. The dusty disks around these stars, gradually cooled downduring their main-sequence phase, could be reheated once the star leavesthe main sequence and enters the luminous post-main-sequence phase. Thefairly large sample we constructed enables us to derive an estimationfor the occurrence of excesses. This fraction of G or K giants withfar-infrared excess appears to be distinctly smaller than amongmain-sequence stars. Since the higher radiation field of giants couldlead to a larger evaporation rate of the circumstellar debris, this factdoes not conflict with our hypothesis.
|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.
|The 1.5-1.7 micrometer spectrum of cool stars: Line identifications, indices for spectral classification and the stellar content of the Seyfert galaxy NGC 1068|
The first aim of this paper is to determine which lines or narrowmolecular bands in the H-band spectra of cool stars could be of interestfor the classification of K-M stars. For this purpose we present highquality, medium resolution (R approximates 1500) spectra of field stars(mostly K-M giants and supergiants) and compare them with detailedsynthetic spectra computed on the basis of existing model atmospheresfor red giants. The agreement between theoretical and observed spectrais good and virtually all the observed features can be accounted for bylines of (12)CO, (13)CO, OH, Mg, Al, Si, Ca and Fe. We analyze in detailthe relative contribution of these and other species and conclude thatthe feature at 1.62 micrometers which is weak in early K but very strongin late M stars, is mainly due to the CO(6-3) band-head, while that at1.59 micrometers, which is prominent in all stars later than G, isprimarily attributable to silicon up to early M types, while in late Mstars this feature is strongly contaminated by OH lines. We choose thesetwo features as 'spectral classificators' and measure their equivalentwidths in more than 40 G, K, M giants and supergiants. From these datait is found that CO 1.62 in giants increases rapidly and with arelatively small scatter going to later spectral types. Supergiants havedeeper CO(6-3) and display a larger scatter. The (1.62)/(2.29) ratiosteadily increases going to cooler stars but does not vary significantlywith luminosity class. A very useful ratio is (1.62)/(1.59) whichincreases by a large factor from early K to late M stars and couldtherefore be a powerful tool to identify and estimate the averagespectral type of cool stars in complex objects like active galaxynuclei. To demonstrate such a possibility we also present long slitspectra of the Seyfert galaxy NGC 1068 where the equivalent widths ofall stellar features are found to decrease in the central 4 arcsecaround the nucleus but the (1.62)/(1.59) ratio, and hence the averagestellar temperature, does not change significantly. The estimatedaverage spectral type is late-K which is compatible with either an oldand very metallic bulge population or a younger one associated with arecent starburst. These data also show that the non-stellar continuumaccounts for approximately 30% and approximately equal to or greaterthan 80% of the flux at 1.62 and 2.3 micrometers respectively in thecentral 4.4 arcsec. The features around 1.6 micrometers are thus muchless diluted than CO(2, 0) and hence offer advantages for studies of thestellar content in such objects. The non-stellar nuclear emission isvery red and most probably associated with a hot (T approximately equalor greater than 800 K) dust component.
|Some Variable Stars in the SRS Catalogue|
|Cyanogen Strengths, Luminosities, and Kinematics of K Giant Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..161J&db_key=AST
|Narrow-Band and Broad-Band Photometry of Red Stars. III. Southern Giants|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJ...161..199E&db_key=AST
|Spectrophotometric methods for determining stellar luminosity.|