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Везани чланци
S0 galaxies in Fornax: data and kinematics
We have obtained long-slit spectroscopy for a sample of nine S0 galaxiesin the Fornax Cluster using the FORS2 spectrograph at the 8.2-m EuropeanSouthern Observatory (ESO) Very Large Telescope (VLT). From these data,we have extracted the kinematic parameters, comprising the meanvelocity, velocity dispersion and higher moment h3 andh4 coefficients, as a function of position along the majoraxes of these galaxies. Comparison with published kinematics indicatesthat earlier data are often limited by their lower signal-to-noise ratioand relatively poor spectral resolution. The greater depth and higherdispersion of the new data mean that we reach well beyond the bulges ofthese systems, probing their disc kinematics in some detail for thefirst time. Qualitative inspection of the results for individualgalaxies shows that they are not entirely simple systems, perhapsindicating a turbulent past. None the less, we are able to derivereliable circular velocities for most of these systems, which points theway towards a study of their Tully-Fisher relation. This study, alongwith an analysis of the stellar populations of these systems out tolarge galactocentric distances, will form the bases of future papersexploiting these new high-quality data, hopefully shedding new light onthe evolutionary history of these systems.
| Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. VIII. The late-type stellar component
We present results of an investigation of the X-ray properties, agedistribution, and kinematical characteristics of a high-galacticlatitude sample of late-type field stars selected from the ROSAT All-SkySurvey (RASS). The sample comprises 254 RASS sources with opticalcounterparts of spectral types F to M distributed over six study areaslocated at |b| 20 °, and Dec ≥ -9 °. A detailed studywas carried out for the subsample of ~200 G, K, and M stars. Lithiumabundances were determined for 179 G-M stars. Radial velocities weremeasured for most of the 141 G and K type stars of the sample. Combinedwith proper motions these data were used to study the age distributionand the kinematical properties of the sample. Based on the lithiumabundances half of the G-K stars were found to be younger than theHyades (660 Myr). About 25% are comparable in age to the Pleiades (100Myr). A small subsample of 10 stars is younger than the Pleiades. Theyare therefore most likely pre-main sequence stars. Kinematically the PMSand Pleiades-type stars appear to form a group with space velocitiesclose to the Castor moving group but clearly distinct from the LocalAssociation.Based on observations collected at the German-Spanish AstronomicalCentre, Calar Alto, operated by the Max-Planck-Institut fürAstronomie, Heidelberg, jointly with the Spanish National Commission forAstronomy, and at the European Southern Observatory, La Silla, Chile.Tables A2-A4 are only available in electronic form athttp://www.edpsciences.org
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are 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/418/989
| Statistical cataloging of archival data for luminosity class IV-V stars. II. The epoch 2001 [Fe/H] catalog
This paper describes the derivation of an updated statistical catalog ofmetallicities. The stars for which those metallicities apply are ofspectral types F, G, and K, and are on or near the main sequence. Theinput data for the catalog are values of [Fe/H] published before 2002February and derived from lines of weak and moderate strength. Theanalyses used to derive the data have been based on one-dimensional LTEmodel atmospheres. Initial adjustments which are applied to the datainclude corrections to a uniform temperature scale which is given in acompanion paper (see Taylor \cite{t02}). After correction, the data aresubjected to a statistical analysis. For each of 941 stars considered,the results of that analysis include a mean value of [Fe/H], an rmserror, an associated number of degrees of freedom, and one or moreidentification numbers for source papers. The catalog of these resultssupersedes an earlier version given by Taylor (\cite{t94b}).Catalog is only available in electronic form at the CDS via anonymousftp cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/731
| Statistical cataloging of archival data for luminosity class IV-V stars. I. The epoch 2001 temperature catalog
This paper is one of a pair in which temperatures and metallicitycatalogs for class IV-V stars are considered. The temperature catalogdescribed here is derived from a calibration based on stellar angulardiameters. If published calibrations of this kind are compared by usingcolor-index transformations, temperature-dependent differences among thecalibrations are commonly found. However, such differences are minimizedif attention is restricted to calibrations based on Johnson V-K. Acalibration of this sort from Di Benedetto (\cite{dib98}) is thereforetested and adopted. That calibration is then applied to spectroscopicand photometric data, with the latter predominating. Cousins R-Iphotometry receives special attention because of its high precision andlow metallicity sensitivity. Testing of temperatures derived from thecalibration suggests that their accuracy and precision are satisfactory,though further testing will be warranted as new results appear. Thesetemperatures appear in the catalog as values of theta equiv5040/T(effective). Most of these entries are accompanied by measured orderived values of Cousins R-I. Entries are given for 951 stars.Catalog is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/721
| Chemical abundances in cool metal rich disk dwarf stars
The present study of spectra of twelve metal-rich cool dwarf stars,carefully selected in order to cover a range of temperatures ( ~ 4400 -6000 K), is a follow up on Feltzing & Gustafsson(1998)\nocite{feltzing} with the aim to understand the apparentover-ionization and anomalous elemental abundances found by them for theK dwarf stars in their sample. Our method of analysis employs syntheticspectra of the full spectrum both to constrain the continuum level andto derive abundances. It is shown that by using this method and imposinga strict excitation equilibrium (possible to do because of the care inselection of observed Fe i lines) we are able to show that metal-rich Kdwarf stars do not show anomalous stellar abundances, as indicated inFeltzing & Gustafsson (1998), and can, with reasonable efforts, beanalyzed in order to increase the number of metal-rich stars with usefulchemical abundances. With abundance analysis by means of spectrumsynthesis and assuming Local Thermodynamic Equilibrium (LTE) theabundances of Na, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, and Nd have beenderived. Also ionization balance is satisfied for Fe and Cr aftercorrecting the stellar effective temperatures such that both ionizationand excitation equilibrium were satisfied. In addition, spectra fromfive cool dwarf stars of the Feltzing & Gustafsson (1998) samplehave been analyzed with the methods used in this work. They showessentially the same abundance patterns as the new stars in this sample.Based on observations made at ESO, La Silla}
| Removal of the calcium underabundance in cool metal rich Galactic disk dwarfs
An apparent Ca underabundance for cool metal rich disk dwarfs wasderived by Feltzing & Gustafsson (1998)nocite{feltzing}. This wassuggested to be a NLTE effect, following the prediction by Drake (1991).New NLTE calculations with MARCS atmospheres and opacities show thatdeviations from LTE are very small and can not explain theunderabundance. It is shown that the underabundance was primarily due toerroneously calculated atomic line broadening parameters (van der Waalsbroadening). Part of the underabundance was also due to the decision notto change photometrically determined stellar parameters to satisfy theFe i excitation balance. Based on observations made at ESO, La Silla
| Color indices of the Sun and Hyades stars in the WBVR system
Using an original setup at high altitudes, we measured the color indicesof the Sun in the WBVR photometric system relative to standard stars: (W- B)_solar = -0.05, (B - V)_solar = +0.67, and (V - R)_solar = +0.53. Wepresent the WBVR photometry for the Hyades members selected by vanBueren by their space velocities. The solar position is shown intwo-color diagrams relative to Hyades stars and bright G2 V stars. Acomparison of our results with Kurucz's models reveals a discrepancybetween the metallicities of the models and the Hyades members.
| Identification of a Complete Sample of Northern ROSAT All-Sky Survey X-Ray Sources. III. The Catalog
We present a catalog of optical identifications of a representativesample of northern ( delta > -9 deg) ROSAT All-Sky Survey (RASS)sources. A full identification has been carried out for a count-rate-and area-limited complete RASS subsample comprising 674 sources. Allsources are within six study areas outside the Galactic plane (| b |> 19.dg6), one area being near the north Galactic pole and one nearthe north ecliptic pole.
| Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. VI. K to M-type stars south of Taurus-Auriga
We present first results of a spectroscopic study of lithium absorptionlines in late-type stars at high galactic latitude. The investigatedstars were identified previously as optical counterparts of ROSATAll-Sky Survey sources. They are contained in a complete X-raycount-rate limited representive subsample of the RASS which wascompletely optically identified by our group. No selection criteriaother than requiring RASS count rates larger than 0.03 cts s(-1) wereapplied. The stars are located at galactic latitudes |b(II) | between28°\ and 45°\ in an area ~ 20°\ south of the Taurus-Aurigastar forming region. In the sample of 35 stars with spectral typesbetween K0 and M5 we found 9 stars with significant Li i<~mbda6708absorption lines, 8 K stars and 1 M0 star. No lithium was found in starswith spectral types later than M0. The Li i equivalent widths (correctedfor the contribution of Fe i ) are between ~ 150 m Angstroms and ~ 400 mAngstroms . The lithium strength of these stars is consistent with ageson the order of 10-30 Myr. These stars are still in a pre-main sequenceevolutionary stage, and belong to the weak-line Tauri stars.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Seven-Color Photoelectric Photometry of Stars in the Hyades Clusters
Not Available
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| The distance and main sequence of the Hyades cluster based on 145 stars with highly accurate proper motions obtained from work on the catalogues FK 5 and PPM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991A&A...243..386S&db_key=AST
| Determining the temperatures of solar-type stars - Do star spots produce color anomalies?
The available evidence pertaining to color 'anomalies' in Hyades dwarfsare examined in detail in order to understand how the determine thetemperatures of solar-type stars. The evidence indicates that thetemperatures of these stars are not seriously skewed by their spots.Simpler explanations which can produce the observed effects arediscussed.
| A radial-velocity survey of the Hyades
Photoelectric radial-velocity measurements, obtained with external erroras small as 0.1 km/s using the 200-inch Hale telescope at PalomarObservatory during the period 1971-1986, are reported for over 400candidate members (with V magnitude between 6 and 14) of the Hyadescluster. The history of Hyades observations is recalled; the Palomarinstrumentation and observing program are described; the data-reductionand standardization procedures are discussed in detail; and the data arepresented in extensive tables and graphs. About 200 of the stars areclassified as cluster members, including 60 spectroscopic binaries.
| The Color-Magnitude Diagram of the Hyades Cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962ApJ...136...75J&db_key=AST
| The Hyades and Coma Berenices Star Clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJ...122..209J&db_key=AST
| On the structure of the Hyades cluster
Not Available
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| Сазвежђа: | Бик |
| Ректацензија: | 03h43m54.34s |
| Deклинација: | +03°26'46.9" |
| Apparent магнитуда: | 8.971 |
| Proper motion RA: | 128.5 |
| Proper motion Dec: | 35.4 |
| B-T magnitude: | 10.123 |
| V-T magnitude: | 9.067 |
Каталог и designations:
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