내용
사진
사진 업로드
DSS Images Other Images
관련 글
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}
| Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue 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/399/141
| Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV-poor Reflection Nebulae
One of the major challenges to identification of the 3.3, 6.2, 7.7, 8.6,and 11.3 μm interstellar infrared (IR) emission bands with polycyclicaromatic hydrocarbon (PAH) molecules has been the recent detection ofthese bands in regions with little ultraviolet (UV) illumination, sincesmall, neutral PAH molecules have little or no absorption at visiblewavelengths and therefore require UV photons for excitation. We showhere that our ``astronomical'' PAH model, incorporating the experimentalresult that the visual absorption edge shifts to longer wavelength uponionization and/or as the PAH size increases, can closely reproduce theobserved IR emission bands of vdB 133, a UV-poor reflection nebula. Wealso show that single-photon heating of ``astronomical'' PAHs inreflection nebulae near stars as cool as Teff=3000K canresult in observable emission at 6.2, 7.7, 8.6, and 11.3 μm.Illustrative mid-IR emission spectra are calculated for reflectionnebulae illuminated by cool stars with Teff=3500, 4500, and5000 K. These will allow comparison with future Space Infrared TelescopeFacility observations of vdB 135 (Teff=3600K), vdB 47(Teff=4500K), and vdB 101 (Teff=5000K). Thedependence on the effective temperature of the exciting star of theobserved 12 μm IRAS emission (relative to the total far-IR emission)is consistent with the PAH model for3000K<=Teff<=30,000K.
| Lick Spectral Indices for Super-Metal-rich Stars
We present Lick spectral indices for a complete sample of 139 candidatesuper-metal-rich stars of different luminosity classes (MK type from Ito V). For 91 of these stars we were able to identify, in anaccompanying paper, the fundamental atmosphere parameters. This confirmsthat at least 2/3 of the sample consists of stars with [Fe/H] in excessof +0.1 dex. Optical indices for both observations and fiducialsynthetic spectra have been calibrated to the Lick system according toWorthey et al. and include the Fe I indices of Fe5015, Fe5270, andFe5335 and the Mg I and MgH indices of Mg2 and Mg b at 5180Å. The internal accuracy of the observations is found to beσ(Fe5015)=+/-0.32 Å, σ(Fe5270)=+/-0.19 Å,σ(Fe5335)=+/-0.22 Å, σ(Mg2)=+/-0.004 mag,and σ(Mg b)=+/-0.19 Å. This is about a factor of 2 betterthan the corresponding theoretical indices from the synthetic spectra,the latter being a consequence of the intrinsic limitations in the inputphysics, as discussed by Chavez et al. By comparing models andobservations, we find no evidence for nonstandard Mg versus Fe relativeabundance, so [Mg/Fe]=0, on the average, for our sample. Both theWorthey et al. and Buzzoni et al. fitting functions are found tosuitably match the data and can therefore confidently be extended forpopulation synthesis application also to supersolar metallicity regimes.A somewhat different behavior of the two fitting sets appears, however,beyond the temperature constraints of our stellar sample. Its impact onthe theoretical output is discussed, as far as the integratedMg2 index is derived from synthesis models of stellaraggregates. A two-index plot, such as Mg2 versus Fe5270, isfound to provide a simple and powerful tool for probing distinctiveproperties of single stars and stellar aggregates as a whole. The majoradvantage, over a classical CM diagram, is that it is both reddeningfree and distance independent. Based on observations collected at theInstituto Nacional de Astrofísica, Optica y Electrónica(INAOE) ``G. Haro'' Observatory, Cananea (Mexico).
| Observations and Atmospheric Parameters of Super-Metal-rich Candidates
The spectroscopic properties of a sample of 92 Population I bright stars(V<8) with literature values of [Fe/H]>=+0.1 are reviewed in orderto study the metallicity scale at supersolar regimes. For 73 of thesecandidate super-metal-rich (SMR) stars we identified the photosphericfiducial parameters (Teff, logg, [M/H]) from among publishedparameter sets via a comparison of new observations in the wavelengthrange 5034-5398 Å with synthetic spectra derived from the 1997database of Chavez et al. As a main issue in our analysis, we find thata ``genuine'' SMR stellar component in the Galactic disk exists withmore than one-fourth of the stars in our sample fulfilling the criterion[Fe/H]>=0.2 dex, and three of them as rich as [Fe/H]>+0.4 dex.Based on observations collected at the INAOE ``G. Haro'' Observatory,Cananea (Mexico).
| A 13CO Survey of Molecular Clouds in Gemini and Auriga
A large-scale survey for molecular clouds in 13CO(J = 1-0) was performedtoward the Gemini and Auriga regions (170 deg < l <= 196 deg and-10 deg <= b < 10 deg) with velocity coverages of -30 < VLSR< +30 km s-1 and -20 < VLSR < +40 km s-1 for 170 deg < l<= 188 deg and 188 deg < l <= 196 deg, respectively, by usingthe two 4 m millimeter-wave telescopes at Nagoya University. An area of520 deg2 was covered at an 8' grid spacing with a 2.'7 beam, and 29,250positions were observed. Significant 13CO emission (>=1.2 K km s-1 =3 sigma ) is detected at 1032 positions, and 139 distinct 13CO cloudsare identified. Physical properties such as molecular column density,size, and mass are derived for each cloud. Comparison with known H IIregions and other associated visible objects indicates that 98 of the139 clouds are located at ~2 kpc, while the rest lie at <~ 1 kpc. Thecandidates for protostars are selected from IRAS point sources and 141sources are identified as protostellar candidates associated with the13CO clouds. A statistical study of the 13CO clouds and of thecandidates for protostars shows the following results: 1. The massspectra of the 13CO clouds are well represented by a power law,Ncloud(>=Mcloud) = 1.4 x 104(Mcloud/Mȯ)-0.83 - 1.4 for theclouds at ~2 kpc and Ncloud(>=Mcloud) = 3.5 x102(Mcloud/Mȯ)-0.64 - 2.4 for the rest. 2. The line width, DeltaVcomp, and the size, R, of the 13CO clouds show a power-law relationwith an index 0.24 +/- 0.06, where the dispersion in the fitting isfairly large. 3. A virial analysis made for the 13CO clouds indicatesthat the relation between the virial mass, Mvir, and the mass measuredin 13CO, Mcloud, is aproximated well by (Mvir/Mȯ) = 2.0 x101(Mcloud/Mȯ)0.72, which suggests that smaller clouds tend to bemore weakly bound gravitationally than larger clouds or are dispersingif the external pressure is negligible. This is probably the cuase of asmall index value of the line width-size relation. 4. The luminosityfunction of the IRAS point sources associated with 13CO clouds are wellrepresented by a power law withN_⋆(>=L_⋆)=4.0x102L^{-0.29}_⋆-1.9x10 forthose at ~2 kpc and N_⋆(>=L_⋆)=2.3x10L^{-0.27}_⋆-3.2for the rest. 5. The luminosity of the most luminous IRAS point sourcein a given molecular cloud increases systematically with the mass of theassociated cloud. 6. The 13CO clouds associated with IRAS point sources,which are regarded as ongoing star-forming clouds, tend to be moremassive and larger in size and to have higher column densities thanthose without any sign of star formation. These relations are found tobe consistent with those derived in Cygnus by Dobashi, Bernard, &Fukui and in Cepheus-Cassiopeia by Yonekura et al. In order to study thestar formation activities, we studied the ratio of virial mass and themass measured in 13CO, Mvir/Mcloud, and its relation with starformation. It is clearly seen that the star-forming 13CO clouds have lowMvir/Mcloud, and all the clouds with high Mvir/Mcloud exhibit no sign ofstar formation. This suggests that star formation rarely occurs inclouds with overall kinetic energy higher than the gravitational energy.
| 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
| Quantitative spectral classification of galactic disc K-M stars from spectrophotometric measurements
New spectral observations for 47 southern galactic red supergiantsobtained with the new RUBIKON spectrophotometer (developed at theAstronomisches Institut der Ruhr-Universitat Bochum) at the Bochum 61-cmtelescope on La Silla are presented. The spectra range from 4800 to 7700A and their resolution is 10 A. The mean error of absolute fluxes is0.028 mag and that of relative fluxes 0.021 mag. The spectra will beavailable at the Strasbourg Stellar Database (CDS). Together with datataken from recently published spectral catalogues, the new observationshave been used to define spectral indices as measures of the strengthsof the following features: Fe i+TiOalpha_1, Mgb+TiOalpha_0,NaD+TiOgamma'_1, TiOgamma'_0 and TiOgamma_1 systems. The indices havebeen checked against errors introduced by reductions, interstellarreddening and different resolutions of different spectral catalogues,and have been found to be very insensitive to all these effects.Therefore, different catalogues may be combined without any loss ofaccuracy and homogeneity. The mean error of a single index has beenfound to be 0.011 mag. For stars from K4 to M7, a strong temperaturedependence is found for all indices. For the Fe i+TiO and especially theMgb+TiO features, a strong dependence on luminosity has also beenobserved. These indices therefore have been combined to form aluminosity index, while the others together form a spectral index. Thecombined indices have been calibrated in terms of MK data using thestepwise linear regression technique, and may be used for quantitativetwo- dimensional spectral classification of late K- and M-type stars.The mean error of the classification is 0.6 of spectral subtype and 0.8of luminosity class, which is much higher than would be expected fromthe uncertainty of the indices alone (which, e.g., for an M4 giantcorrespond to an uncertainty of 0.1 of spectral subtype and 0.3 ofluminosity class). This may be explained by the uncertainty of theoriginal MK classifications and the variability of some programme stars.
| A Survey of Near-Infrared Emission in Visual Reflection Nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..102..369S&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.
| A Study of the Kinematics of the Local Dark Clouds
Not Available
| 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.
| The excitation of 12 micron emission from very small particles
The results of IRAS observations of visual reflection nebulaeilluminated by stars with effective temperatures between 3000 and 33,000K are presented. The ratio of the energy radiated in the IRAS 12-micronsband to the total energy radiated at far-infrared wavelengths (60 and100 microns) is about 0.2, with little or no dependence on thetemperature of the illuminating star for stellar temperatures betweenabout 5000 and 33,000 K. This is interpreted as requiring that visualphotons as well as ultraviolet photons are capable of exciting12-microns emission from very small particles.
| The luminosity of reflection nebulae
Consideration is given to the connection between the dispersion inHubble's relation for reflection nebulae and their morphologicalcharacteristics. Statistical estimates show that the reflection nebulaeconnected with more opaque dust-gas clouds, compared to those near lessopaque clouds, have large values of Delta-B (the measure of deviationsin Hubble's relation) and a high surface brightness. These propertiesare more pronounced in the Herbig Ae/Be stars. Stars in the nebulaeconnected with more opaque dust-gas clouds were found to exhibit excessreddening, with R above 3.1. It is concluded that the dispersion in theHubble relation is mainly due to the optical depth of the nebulae.
| Supergiants and the Galactic metallicity gradient. II - Spectroscopic abundances for 64 distant F- to M-type supergiants
The metallicity gradient in the Galactic disk from in situ stars withvisual magnitude ranging from 6 to 10 is analyzed. Atmosphericparameters and detailed chemical abundances for 64 Population Isupergiants of spectral types F through M and luminosity classes Iathrough II have been determined. The derived Fe/H ratios ranging from-0.5 to + 0.7 show a mean value of +0.13 with an estimated uncertaintyof + or - 0.2. A subset of 25 supergiants fainter than 7th magnitudelying in the direction of the Galactic center shows a Fe/H mean of +0.18+ or - 0.04, while a similar sample of 15 faint supergiants lying in thedirection of the Galactic anticenter shows a lower Fe/H mean of +0.07 +or - 0.06. For a sample of bright supergiants analyzed by Luck andLambert (1985), the mean abundance pattern for all 64 stars showed thefollowing: deficient C and O along with enhancement of N, indicatingmixing of CNO-cycled material to the stellar surfaces; an apparent Srenhancement attributed to departures from LTE; and an essentially solarpattern of other chemical elements.
| A catalogue of Fe/H determinations, 1984 edition
The present version of the Cayrel de Strobel et al. (1981) catalog ofFe/H abundance ratio determinations contains 1921 values for 1035 stars,which represents an augmentation over the previous publication of 48 and47 percent, respectively. In addition, the literature search conductedis complete up to December, 1983. Stellar metal abundance, effectivetemperature, spectroscopic gravity, spectral type, and photometricindices are covered.
| Nineteen new spectroscopic binaries and the rate of binary stars among F-M supergiants
Nineteen spectroscopic binaries (SBs) have been discovered in radialvelocity measurements made with the CORAVEL spectrophotometer on 181northern F-M supergiants. The rate of detected SBs among northern F-Msupergiants is 21 percent, without any dependence on spectral orluminosity class. The study of the binary F-M supergiants with knownorbital elements indicates that all the systems with a period smallerthan the critical value P(circ) have a nearly circular orbit. The valueof P(circ) depends on the luminosity class, being 400-600 d for class Iband 2000-7000 d for class Ia. This circularization of the orbits may bedue to the transfer of angular momentum during the phase of binary massexchange.
| Status of evolution of F, G, and K field stars contained in the Fe/H abundance ratio catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&A...119....1C&db_key=AST
| The chemical composition of late-type supergiants. IV - Homogeneous abundances and galactic metallicity trends
A reanalysis of equivalent-width data for 19 northern supergiantsconsidered in previous chemical composition studies is conducted withimproved techniques and atomic data in order to place all supergiantabundances on the same scale. Although surface gravities and surfacetemperatures show only minor changes with respect to previously obtainedvalues, microturbulent velocities are increased by an average of 50%,leading to a desaturation of the lines and a consequent decrease inderived abundances. The solar-neighborhood supergiants are thus broughtto within 0.1 dex of the sun and local F-type dwarfs, in view of adecrease in Fe/H abundance ratio values of 0.2 dex. It is also shownthat while most equivalent widths are on the same scale those of thesouthern stars are systematically high with respect to the remainingvalues, requiring the exclusion of nine stars from consideration inlocal and galactic metallicity discussions.
| The chemical compositions of 26 distant late-type supergiants and the metallicity gradient in the galactic disk
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980ApJ...241..218L&db_key=AST
| Molecular clouds associated with reflection nebulae. I - A survey of carbon monoxide emission
The paper presents 2.6 mm wavelength CO and (C-13)O observations of 130molecular clouds associated with reflection nebulae. Enhanced COemission was found in the vicinity of the illuminating star in abouthalf the objects studied. There is a tendency for the CO peak to beslightly displaced from the star. Many examples of peaks that appear toresult from heating of the cloud by the nearby star are found, whileothers appear to be associated with independent concentrations ofmaterial.
| On the relationship between the apparent magnitudes given in several catalogues and the UBV system.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...15..215O&db_key=AST
| The space distribution and kinematics of supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..602H&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
| Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
| A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
| Notes on Diffuse Galactic Nebulae
Not Available
| Stellar groups, VII. The structure of the Hyades group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960MNRAS.120..540E&db_key=AST
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
