Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| 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.
| Infrared Fe II Emission in Narrow-Line Seyfert 1 Galaxies
We obtained 0.8-2.4 μm spectra at a resolution of 320 kms-1 of four narrow-line Seyfert 1 galaxies in order to studythe near-infrared properties of these objects. We focus on the analysisof the Fe II emission in that region and the kinematics of thelow-ionization broad lines. We show that the 1 μm Fe II lines(λ9997, λ10501, λ10863, and λ11126) are thestrongest Fe II lines in the observed interval. For the first time,primary cascade lines of Fe II arising from the decay of upper levelspumped by Lyα fluorescence are resolved and identified in activegalactic nuclei. Excitation mechanisms leading to the emission of the 1μm Fe II features are discussed. A combination of Lyαfluorescence and collisional excitation is found to be the maincontributor. The flux ratio between near-IR Fe II lines varies fromobject to object, in contrast to what is observed in the optical region.A good correlation between the 1 μm and optical Fe II emission isfound. This suggests that the upper z4F0 andz4D0 levels from which the bulk of the optical FeII lines descend are mainly populated by the transitions leading to the1 μm lines. The width and profile shape of Fe II λ11127, Ca IIλ8642, and O I λ8446 are very similar but significantlynarrower than Paβ, giving strong observational support to thehypothesis that the regions where Fe II, Ca II, and O I are produced arecospatial, interrelated kinematically, and most probably located in theoutermost portion of the broad-line region.
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| Near-Infrared Spectroscopy of the Compact H II Region W51 IRS 2
Medium-resolution (R~460) spectra in the K window have been obtained forthe compact H II regions W51 IRS 2 East and IRS 2 West. Brγ, He I,three lines of [Fe III], and seven lines of molecular hydrogen(H2) have been detected. The unidentified line at 2.288 μmwas also detected with ~2% of the intensity of Brγ. We derive anelectron density of ~105-106 cm-3 inboth IRS 2 East and IRS 2 West from [Fe III] line ratios. In bothregions, observed H2 line ratios indicate that the excitationof H2 is dominated by fluorescence rather than by shocks.
| 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
| Brocchi's Cluster Revealed
Not Available
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The nature of some doubtful open clusters as revealed by HIPPARCOS
We discuss the nature of some galactic open clusters by using propermotions and parallaxes from the Hipparcos and ACT catalogues. We showthat the clusters Collinder 399, Upgren 1, NGC 1252 and Melotte 227 donot exist. Collinder 132 is found to be mainly composed out of membersof an OB association, but there may be a star cluster present in thisarea too. Roeser & Bastian (1994) proposed that NGC 2451 consists oftwo star clusters. We show that NGC 2451 A definitively does exist, NGC2451 B may exist. A star cluster may also be present in the area ofRoslund 5. The Hipparcos data finally confirm the reality of Collinder135.
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&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 survey for rapid variability among early main-sequence A stars
A survey of nonpeculiar early (A0-A5) main-sequence A stars for rapid,low-amplitude variability is presented. The survey is also anindependent test of the main-sequence mass-loss theory proposed byWillson et al. (1986). All observations were gathered with theUniversity of Wisconsin Two-Star Photometer. Several period-searchingmethods are used to analyze time series of differential-photometricdata. This instrument coupled with a computerized high-speed datacollection system was used with small telescopes at Pine BluffObservatory and Table Mountain Observatory. Several period-searchmethods are used to analyze time series of differential-photometricdata. This instrument and data-reduction technique allow millimagnitudelight variations to be detected. The survey also discovered severallow-amplitude Delta Sct stars, all of which are in or blueward of therecognized instability strip.
| The Cloudy Circumstellar Dust Shell of Ww-Vulpeculae Revisited
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...277..184F&db_key=AST
| The Einstein Galactic plane survey. II - Optical observations of Northern Hemisphere X-ray sources
Spectroscopic and photometric observations of 67 Northern-HemisphereX-ray sources from the Einstein Galactic Plane Survey (Hertz andGrindlay, 1984) (HG) are reported. Data obtained at 450-700 nm using the1.5-m telescope at Whipple Observatory and the MMT are combined withpublished observational data in tables, and the identificationalgorithms described by HG are applied. Identifications with opticalobjects are proposed for 45 sources, and it is inferred that most of theothers are noncoronal extragalactic objects. None of the objects can beassigned to the class of low-luminosity accretion sources proposed byHG.
| ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars
A survey of a sample of 672 stars from the Yale Bright Star Catalog(Hoffleit, 1982) has been carried out using speckle interferometry onthe 3.6-cm Canada-France-Hawaii Telescope in order to establish thebinary star frequency within the sample. This effort was motivated bythe need for a more observationally determined basis for predicting thefrequency of failure of the Hubble Space Telescope (HST) fine-guidancesensors to achieve guide-star lock due to duplicity. This survey of 426dwarfs and 246 evolved stars yielded measurements of 52 newly discoveredbinaries and 60 previously known binary systems. It is shown that thefrequency of close visual binaries in the separation range 0.04-0.25arcsec is 11 percent, or nearly 3.5 times that previously known.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| The Einstein galactic plane survey - Statistical analysis of the complete X-ray sample
A flux-limited survey of the galactic plane using the Einstein ImagingProportional Counter has been conducted, discovering 71 point-like X-raysources exceeding a five sigma threshold. These sources arestatistically analyzed, and it is concluded that the number-fluxrelation for low-flux galactic plane X-ray sources has a slope of -1.10,significantly steeper than the about -0.5 found for bright sources byUhuru and Ariel V. The sample contains about 46 percent coronal sources,about 31 percent extragalactic sources, and about 23 percent galacticaccretion sources. Thus, about 16 new galactic accretion sources havebeen discovered. The approximate number density of such sources isconsistent with their being cataclysmic variables and other accretingwhite dwarfs. Faint galactic plane sources are significantlyconcentrated toward the galactic bulge, and those near the bulge exhibita flatter number-flux relation than those at higher galactic latitudesand longitudes. This indicates a different source population with a lessisotropic distribution.
| Apparent radii and other parameters for 416 B5 V-F5 V stars of the catalogue of the Geneva Observatory
Apparent radius, visual brightness, effective temperature and absoluteradius for 416 B5 v-F5 v stars of the catalogue of the GenevaObservatory (Rufener, 1976) have been determined. Twenty-eight stars,anomalous in log a" versus (m~)o diagrams, have been singled out. A goodcorrelation for seven stars, in common with the list of Hanbury Brown etal. (1974), has been found. Similar parameters determined for 279 B5v-F5 v stars of two preceding papers (Fracassini et al., 1973, 1975)have allowed us to determine the averaged diagrams , and versus (B -V)0 for 695 B5 v-F5 v stars. Moreover, in the present paper a goodcorrelation versus and carefulrelation = -7.40 + 3.31 for B5v-F5 V stars have been determined. Plain correlations between log R/R0and blanketing parameter m2 for some spectral types seem to point outthat there are real differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HRdiagram (Houck and Fesen, 1978). Systematic differences between double(spectroscopic and visual) and single stars are found. In particular,the averaged relation versus shows that A2v-F5 v double stars may have a higher metallicity index m2 and smallerabsolute radii than single stars. Finally, the diagram log v sin iversus log R/R0 confirms some properties of binary systems found byother researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura andKondo, 1978)
| Narrow-band photometry of Beta Lyrae in 1971
Observations of Beta Lyrae (with HR 6997 as the principal companionstar) are presented, principally of certain strong lines and neighboringcontinuum regions obtained through interference filters of bandwidthsranging from 27.0 to 33.7 A. Light curves in the 3 blue and 3 red bandsare shown, and color indices and emission intensity indices aretabulated. Moreover, a photometric index of emission line strength,analogous to the spectroscopic index of Batten and Sahade (1973), isderived. It is suggested that the H alpha emission comes from a largerregion around the binary star than does the helium emission and isasymmetrical, being weakest near quadrature when the primary star isapproaching earth. The helium emission, by contrast, is moresymmetrical, and varies with binary phase by a larger fractional amount.
| Spectral classification from the ultraviolet line features of S2/68 spectra. III - Early A-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33...15C&db_key=AST
| Rotational Velocities of a0 Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..101D&db_key=AST
| Lichtwechsel und Extinktion des Veränderlichen WW Vulpeculae
Not Available
| Four-color and Hβ photometry for the brighter AO type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..109C&db_key=AST
| The Nearby Poor Cluster Collinder 399
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970PASP...82..640H&db_key=AST
| Etude pour chaque champ de l'absorption et de la repartition des vitesses radiales EN fonction de la distance.
Not Available
| Spectral Classification of 533 B8-A2 Stars and the Mean Absolute Magnitude of a0 V Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..159O&db_key=AST
| La mesure des vitesses radiales au prisme objectif. VII - 2e liste de vitesses radiales déterminées au prisme objectif à vision directe
Not Available
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Volpetta |
| Ascensione retta: | 19h25m22.40s |
| Declinazione: | +20°16'17.0" |
| Magnitudine apparente: | 6.31 |
| Distanza: | 122.549 parsec |
| Moto proprio RA: | -1.4 |
| Moto proprio Dec: | -15.8 |
| B-T magnitude: | 6.281 |
| V-T magnitude: | 6.285 |
Cataloghi e designazioni:
|
