Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Empirical calibration of the lambda 4000 Å break
Empirical fitting functions, describing the behaviour of the lambda 4000Ä break, D4000, in terms of effective temperature,metallicity and surface gravity, are presented. For this purpose, thebreak has been measured in 392 stars from the Lick/IDS Library. We havefollowed a very detailed error treatment in the reduction and fittingprocedures, allowing for a reliable estimation of the breakuncertainties. This calibration can be easily incorporated into stellarpopulation models to provide accurate predictions of the break amplitudefor, relatively old, composite systems. Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Photometric Separation of Stellar Properties Using SDSS Filters
Using synthetic photometry of Kurucz model spectra, we explore thecolors of stars as a function of temperature, metallicity, and surfacegravity with Sloan Digital Sky Survey (SDSS) filters, u'g'r'i'z'. Thesynthetic colors show qualitative agreement with the few publishedobservations in these filters. We find that the locus of synthetic starsis basically two-dimensional for 4500 < T < 8000 K, whichprecludes simultaneous color separation of the three basic stellarcharacteristics we consider. Colors including u' contain the mostinformation about normal stellar properties; measurements in this filterare also important for selecting white dwarfs. We identify two differentsubsets of the locus in which the loci separate by either metallicity orsurface gravity. For 0.5 < g' - r' < 0.8 (corresponding roughly toG stars), the locus separates by metallicity; for photometric error of afew percent, we estimate metallicity to within ~0.5 dex in this range.In the range -0.15 < g' - r' < 0.00 (corresponding roughly to Astars), the locus shows separation by surface gravity. In both cases, weshow that it is advantageous to use more than two colors whendetermining stellar properties by color. Strategic observations in SDSSfilters are required to resolve the source of a ~5% discrepancy betweensynthetic colors of Gunn-Stryker stars, Kurucz models, and externaldeterminations of the metallicities and surface gravities. The syntheticstar colors can be used to investigate the properties of any normal starand to construct analytic expressions for the photometric prediction ofstellar properties in special cases.
| H gamma and H delta Absorption Features in Stars and Stellar Populations
The H gamma and H delta absorption features are measured in a sample of455 (out of an original 460) Lick/IDS stars with pseudo--equivalentwidth indices. For each Balmer feature, two definitions, involving anarrow (~20 Angstroms) and a wide (~40 Angstroms) central bandpass, aremeasured. These four new Balmer indices augment 21 indices previouslydetermined by Worthey et al., and polynomial fitting functions that giveindex strengths as a function of stellar temperature, gravity, and[Fe/H] are provided. The new indices are folded into models for theintegrated light of stellar populations, and predictions are given forsingle-burst stellar populations of a variety of ages and metallicities.Contrary to our initial hopes, the indices cannot break a degeneracybetween burst age and burst strength in post-starburst objects, but theyare successful mean-age indicators when used with sensitive metallicityindicators. An appendix gives data, advice, and examples of how totransform new spectra to the 25-index Lick/IDS system.
| 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.
| Spectral indices in cooling flow galaxies: evidence of star formation
Spectroscopic observations of central dominant cluster galaxies, withand without cooling flows, are presented. Through the analysis ofabsorption spectral features, namely the strength of the magnesiumabsorption at lambda5175A and the lambda4000-A break, both in the galaxycentres and as a function of radius, we have been able to estimate theongoing star formation induced by the large amounts of gas accreted onto cooling flow galaxies. A correlation between the central spectralindices and the mass accretion rate is found in the sense that galaxieslocated in clusters with large cooling flows exhibit lower Mg_2 andD_4000 indices. A similar correlation with D_4000 was previouslyreported by Johnstone, Fabian & Nulsen. Our work, with the inclusionof the correlation in Mg_2, adds further weight to the conclusion thatthese spectral anomalies are caused by recent star formation. Theapplication of simple stellar population models reveals that themeasured indices are explained if a relatively small fraction of thetotal mass flow (5-17 per cent) is forming new stars with a normalinitial mass function. However, we argue that this is only a lowerlimit, and conclude that a large fraction of the gas accreted inside thegalaxy could be forming stars. We find that spectral gradients in somecooling flow galaxies flatten in the internal regions(r<~r_e), where emission lines are usuallydetected. Gradients measured in the inner galaxy regions are, in themean, lower than those of normal ellipticals, and exhibit a hint of acorrelation with M_solar. Application of the same population models tothe observed spectral gradients allows us to conclude that the ongoingstar formation is concentrated towards the inner parts of the coolingflow galaxies and, therefore, the star formation does not follow theX-ray derived mass accretion profiles. Simultaneously, the spectralindices in the outer regions of some galaxies with and without coolingflow attain extremely low values, suggesting that they could be hostingstar formation with an origin that is not related to the cooling flows.
| Old stellar populations. 5: Absorption feature indices for the complete LICK/IDS sample of stars
Twenty-one optical absorption features, 11 of which have been previouslydefined, are automatically measured in a sample of 460 stars. FollowingGorgas et al., the indices are summarized in fitting functions that giveindex strengths as functions of stellar temperature, gravity, and(Fe/H). This project was carried out with the purpose of predictingindex strengths in the integrated light of stellar populations ofdifferent ages and metallicities, but the data should be valuable forstellar studies in the Galaxy as well. Several of the new indices appearto be promising indicators of metallicity for old stellar populations. Acomplete list of index data and atmospheric parameters is available incomputer-readable form.
| Theoretical colours and isochrones for some Hubble Space Telescope colour systems. II
A grid of synthetic surface brightness magnitudes for 14 bandpasses ofthe Hubble Space Telescope Faint Object Camera is presented, as well asa grid of UBV, uvby, and Faint Object Camera surface brightnessmagnitudes derived from the Gunn-Stryker spectrophotometric atlas. Thesynthetic colors are used to examine the transformations between theground-based Johnson UBV and Stromgren uvby systems and the Faint ObjectCamera UBV and uvby. Two new four-color systems, similar to theStromgren system, are proposed for the determination of abundance,temperature, and surface gravity. The synthetic colors are also used tocalculate color-magnitude isochrones from the list of theoretical tracksprovided by VandenBerg and Bell (1990). It is shown that by using theappropriate filters it is possible to minimize the dependence of thiscolor difference on metallicity. The effects of interstellar reddeningon various Faint Object Camera colors are analyzed as well as theobservational requirements for obtaining data of a given signal-to-noisefor each of the 14 bandpasses.
| 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.
| Some notes on the Gunn-Stryker spectrophotometry and synthetic VRI colors
Cousins VRI photometry is presented for 26 stars with continuous scansby Gunn and Stryker. This photometry is combined with literature dataand a few unpublished results to critique synthetic colors from theGunn-Stryker scans. For V - R, it is found that all pertinent resultsare consistent at the several-mmag level. For R - I, however, systematicdifferences are found which are most simply interpreted as a declinationeffect in the Gunn-Stryker scans. In addition, it is found that theGunn-Stryker synthetic colors are unexpectedly noisy, with sigma perdatum of about 0.02 mag. It is suggested that future users of theGunn-Stryker data keep both these effects in mind.
| Old stellar populations. II - an analysis of K-giant spectra
Eleven strong absorption features are studied in a sample of 110 K-giantstars, based on spectra taken at 9-A resolution, including such featuresas CN 4170 A, G-band, H-beta, Mg b, MgH, two Fe lines, NaD, and two TiObands. The surface features sensitive to surface gravity are determined;it is noted that the most accurate gravity indicator appears to be theindex Mg2. Previously identified super metal-rich stars generally showthe strongest lines of iron, CN, Mg, and NaD; essentially allintermediate and strong blends are also markedly enhanced in thesestars. Finally, iron-line residual Delta-Fe is shown to be a goodmeasure of metallicity and at the same time independent of surfacegravity.
| Stellar spectrophotometric atlas, wavelengths from 3130 to 10800 A
Over the course of the past 10 years, a large body of homogeneousspectrophotometric data on relatively bright stars has been gathered toserve as a library with which to synthesize galaxy spectra in populationstudies. As the data might be generally useful, they are presented inthree tables. One hundred seventy-five (175) stars were selected, mostfrom the Navy photometric catalog. Covered are complete ranges ofspectral type and luminosity class. Normalized spectral energydistributions of these stars in pictorial form are provided along withtables of calculated colors, scan line and continuum indices, and someinformation on the relation of the scan colors to real photometricsystems.
| Evolutionary synthesis of the stellar population in elliptical galaxies. III - Detailed optical spectra
The evolutionary synthesis technique is used to construct populationmodels for giant elliptical galaxies, using detailed spectrophotometricdata for the galaxies and for stars obtained with the Oke multichannelspectrometer on the Hale telescope. It is found that ellipticals arewell represented by an old, metal-rich population with a turnoff at B-Vof about 0.80 and a turnoff mass function slope of x approximately equalto or less than 1, plus a quite significant contribution from starsabove the turnoff. The nature of these objects is discussed, and it isconcluded that the present data and astrophysical constraints cannotdistinguish between a small young population and a blue stragglerpopulation augmented by a few O stars.
| Etude pour chaque champ de l'absorption et de la repartition des vitesses radiales EN fonction de la distance.
Not Available
| La mesure des vitesses radiales au prisme objectif - X - 4e liste de vitesses radiales déterminées au prisme objectif à vision directe
Not Available
| La mesure des vitesses radiales au prisme objectif. IX - 3e liste de vitesses radiales déterminées au prisme objectif à vision directe
Not Available
| Stellar Spectra and Colors in a Milky way Region in Cassiopeia.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJS....2..123F&db_key=AST
|
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: | Cassiopeia |
| Ascensió Recta: | 01h49m59.37s |
| Declinació: | +62°09'03.6" |
| Magnitud Aparent: | 8.126 |
| Distancia: | 202.02 parsecs |
| Moviment propi RA: | -7.1 |
| Moviment propi Dec: | -0.8 |
| B-T magnitude: | 9.195 |
| V-T magnitude: | 8.215 |
Catàlegs i designacions:
|
INHABITED SKY
