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Reliability Checks on the Indo-US Stellar Spectral Library Using Artificial Neural Networks and Principal Component Analysis
The Indo-US coudé feed stellar spectral library (CFLIB) madeavailable to the astronomical community recently by Valdes et al. (2004,ApJS, 152, 251) contains spectra of 1273 stars in the spectral region3460 to 9464Å at a high resolution of 1Å (FWHM) and a widerange of spectral types. Cross-checking the reliability of this databaseis an important and desirable exercise since a number of stars in thisdatabase have no known spectral types and a considerable fraction ofstars has not so complete coverage in the full wavelength region of3460-9464Å resulting in gaps ranging from a few Å to severaltens of Å. We use an automated classification scheme based onArtificial Neural Networks (ANN) to classify all 1273 stars in thedatabase. In addition, principal component analysis (PCA) is carried outto reduce the dimensionality of the data set before the spectra areclassified by the ANN. Most importantly, we have successfullydemonstrated employment of a variation of the PCA technique to restorethe missing data in a sample of 300 stars out of the CFLIB.
| Elemental abundances in the atmosphere of clump giants
Aims.The aim of this paper is to provide the fundamental parameters andabundances for a large sample of local clump giants with a highaccuracy. This study is a part of a big project, in which the verticaldistribution of the stars in the Galactic disc and the chemical anddynamical evolution of the Galaxy are being investigated. Methods:.The selection of clump stars for the sample group was made applying acolour-absolute magnitude window to nearby Hipparcos stars. Theeffective temperatures were estimated by the line depth ratio method.The surface gravities (log {g}) were determined by two methods (thefirst one was the method based on the ionization balance of iron and thesecond one was the method based on fitting of the wings of the Ca I6162.17 Å line). The abundances of carbon and nitrogen wereobtained from the molecular synthetic spectrum, and the Mg and Naabundances were derived using the non-LTE approximation. The "classical"models of stellar evolution without atomic diffusion androtation-induced mixing were employed. Results: .The atmosphericparameters ({T_eff}, log {g}, [Fe/H], {Vt}) and Li, C, N, O,Na, Mg, Si, Ca, and Ni abundances in 177 clump giants of the Galacticdisc were determined. The underabundance of carbon, overabundance ofnitrogen, and "normal" abundance of oxygen were detected. A small sodiumoverabundance was found. A possibility of a selection of the clumpgiants based on their chemical composition and the evolutionary trackswas explored. Conclusions: .The theoretical predictions based onthe classical stellar evolution models are in good agreement with theobserved surface variations of the carbon and nitrogen just after thefirst dredge-up episode. The giants show the same behaviour of thedependencies of O, Mg, Ca, and Si (α-elements) and Ni (iron-peakelement) abundances vs. [Fe/H] as dwarfs do. This allows us to use suchabundance ratios to study the chemical and dynamical evolution of theGalaxy.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/165}
| 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.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable 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/qcar?J/A+A/367/521
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Absolute declinations with the photoelectric astrolabe at Calern Observatory (OCA)
A regular observational programme with a photoelectric astrolabe havebeen performed at ``Observatoire du Calern" (Observatoire de laCôte d'Azur, OCA, phi = +43() o44′55.011″; lambda =-0() h27() m42.44() s, Calern, Caussols, France) for the last twentyyears. It has been almost fully automatized between 1984 and 1987. Since1988 the photoelectric astrolabe was used without any modification. Inaddition to determining the daily orientation of the local vertical, theyearly analysis of the residuals permits to derive corrections to theused star catalogue \cite[(Vigouroux et al. 1992)]{vig92}. A globalreduction method was applied for the ASPHO observations. The new form ofthe equations \cite[(Martin & Leister 1997)]{mar97} give us thepossibility of using the entire set of the observing program using datataken at two zenith distances (30() o and 45() o). The program containsabout 41648 stars' transits of 269 different stars taken at``Observatoire du Calern" (OCA). The reduction was based on theHIPPARCOS system. We discuss the possibility of computing absolutedeclinations through stars belonging simultaneously to the 30() o and45() o zenith distances programmes. The absolute declination correctionswere determined for 185 stars with precision of 0.027arcsec and thevalue of the determined equator correction is -0.018arcsec +/-0.005arcsec . The instrumental effects were also determined. The meanepoch is 1995.29. Catalogue only available at CDS in electronic from viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Library of high-resolution UES echelle spectra of F, G, K and M field dwarf stars
We present a library of Utrecht echelle spectrograph (UES) observationsof a sample of F, G, K and M field dwarf stars covering the spectralrange from 4800 \ Angstroms to 10600 \ Angstroms with a resolution of55000. These spectra include some of the spectral lines most widely usedas optical and near-infrared indicators of chromospheric activity suchas Hβ , Mg i b triplet, Na i D1, D2, He iD3, Hα , and Ca ii IRT lines, as well as a large numberof photospheric lines which can also be affected by chromosphericactivity. The spectra have been compiled with the aim of providing a setof standards observed at high-resolution to be used in the applicationof the spectral subtraction technique to obtain the active-chromospherecontribution to these lines in chromospherically active single andbinary stars. This library can also be used for spectral classificationpurposes. A digital version with all the spectra is available via ftpand the World Wide Web (WWW) in both ASCII and FITS formats. Based onobservations made with the William Herschel Telescope operated on theisland of La Palma by the Isaac Newton Group at the Spanish Observatoriodel Roque de Los Muchachos of the Instituto de Astrof\'{\i
| 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 photometric variability of K giants
We have photometrically monitored 49 of the more than 200 K giants inthe Yale Catalog of Bright Stars (YCBS) which are named or suspectedvariable stars. Only two (HR 3275 and HR 5219) are clearly variable; afew more program stars and K- and M-giant comparison stars aremarginally variable. Most of these appear to be RS Canum Venaticorum orSR variables.
| Corrections to FK4 Positions of Stars Observed at Paris Astrolabe
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102..389N&db_key=AST
| Corrections to the right ascension to be applied to the apparent places of 1217 stars given in "The Chinese Astronomical Almanach" for the year 1984 to 1992.
Not Available
| Velocity dispersions and mean abundances for Roman's G5-K1 spectroscopic groups
The velocity dispersions and U-V distributions of Roman's (1950, 1952)four spectroscopic groups (weak CN, weak line, strong line, and 4150)are compared with those of groups based only on Fe/H ratio. It is shownthat the velocity-dispersion gradient for the Roman spectroscopic groupsis greater than for the comparison group for all three velocitycomponents and for the mean orbital eccentricity, with a clearly definedminimum for the strong-line stars and a sharp upturn for the 4150 stars.The results suggest that the Roman's assignment to distinctspectroscopic groups results in more homogeneous groups than the binningon the basis of metallicity.
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
| CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
| Chromospheric activity in evolved stars - The rotation-activity connection and the binary-single dichotomy
A tabulation of measured values of the Ca II H and K (S) index aretransformed to the original Mount Wilson definition of the index. Thetabulation includes main-sequence, evolved, single, and tidally coupled(RS CVn) binary stars. The (S) indices are analyzed against Wilson's(1976) I(HK) intensity estimates, showing that Wilson's estimates areonly a two-state indicator. Ca II H and K fluxes are computed andcalibrated with published values of rotation periods. It is found thatthe single and binary stars are consistent with a single relationshipbetween rotation and Ca II excess emission flux.
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
| 10830 A He I observations of 455 stars
A comparison with K line, X-ray and other data, of 10830 A equivalentwidths (EW) measurements in 890 image tube spectra of 455 stars showsthat for the case of G stars, the EW correlates well with K lineintensity. Good correlation is also found between 10830 A EW and softX-ray fluxes, confirming the excitation of the line by coronal softX-rays, which can serve as a measure of coronal emission. It is alsofound that, in contradiction to published models, 10830 A is weak orabsent in O, B and A stars, and is absent in F and M supergiants.Moderate to high 10830 A EW is frequent in F and M dwarfs, G and Ksupergiants, and class K3 III. The 58 stars whose 10830 A EW was foundto be of 300 A or more should be relatively intense X-ray emitters.Almost all RS CVn stars show strong 10830 A absorption, and T Tauristars show both absorption and emission.
| Magnetic structure in cool stars. VI - CA II H and K fluxes from evolved stars
Quantitative measurements of the Ca II H and K flux of 335 evolved starsare presented and discussed. The results show that there is a largespread in the fluxes from stars with (B-V) less than 0.95 while the CaII H and K flux of single stars with (B-V) greater than 0.95 correlateswith color with little spread. Short-period binaries show a relativelyhigh Ca II H and K flux indicating that high fluxes result from rapidrotation independent of spectral type. The data are consistent with thehypothesis that the emission depends on dynamo action in the convectiveenvelope, the dynamo efficiency decreasing with decreasing rotationrate. The evolution of the emission is discussed as a function ofstellar mass. It is shown that stars which leave the main sequence withrelatively low or high rotational velocities show relatively low or highemission values, respectively. The flux lasts up to higher (B-V) valuesfor progressively higher masses.
| Absolute magnitudes of stars from widths of chromospheric CaII emission lines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...205..823W&db_key=AST
| Determination of atmospheric parameters for G and K giants by means of photoelectric indices.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....15..123H&db_key=AST
| The intensity of ScI (6305 A) in late stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.147..303G&db_key=AST
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
| The Effect of Metal Abundance on K-Line Absolute Magnitudes
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968PASP...80..717Y&db_key=AST
| Abundances of sodium, magnesium and calcium in K-type giant stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968MNRAS.140...21P&db_key=AST
| Narrow band photometry in the study of stellar populations. I. The sodium D lines in late-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.134..135P&db_key=AST
| UBV photometry of 550 F, G and K type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.133..475A&db_key=AST
| Narrow band photoelectric Hα photometry in late-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.133..449P&db_key=AST
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| קבוצת-כוכבים: | לינכס |
| התרוממות ימנית: | 06h46m49.50s |
| סירוב: | +57°10'09.0" |
| גודל גלוי: | 5.35 |
| מרחק: | 63.735 פארסק |
| תנועה נכונה: | 14.1 |
| תנועה נכונה: | -39 |
| B-T magnitude: | 6.565 |
| V-T magnitude: | 5.443 |
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