Contents
Images
Upload your image
DSS Images Other Images
Related articles
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
| The Age Range of Hyades Stars
On the basis of canonical models, the age of Hyades supercluster stars,whether in the Hyades and Praesepe clusters or the noncluster field,ranges from (5-6) x 10^8 to 10^9 yr. The difference between the parallaxderived from the supercluster motion and that obtained from Hipparcosobservations has a dispersion only twice that of the mean dispersion ofthe individual Hipparcos values. The supercluster appears not to containred giants on the first ascent of the red giant branch, but onlyasymptotic giant branch (``clump'') stars. The masses obtained forindividual components of binary stars in the supercluster show adispersion of less than 10% when compared with model predictions.
| An extensive Delta a-photometric survey of southern B and A type bright stars
Photoelectric photometry of 803 southern BS objects in the Deltaa-system as detection tool for magnetic chemically peculiar (=CP2) starshas been carried out and compared to published spectral types. Thestatistical yield of such objects detected by both techniques ispractically the same. We show that there are several factors whichcontaminate the search for these stars, but this contamination is onlyof the order of 10% in both techniques. We find a smooth transition fromnormal to peculiar stars. Our sample exhibits the largest fraction ofCP2 stars at their bluest colour interval, i.e. 10% of all stars in thecolour range -0.19 <= B-V < -0.10 or -0.10 <= b-y < -0.05.No peculiar stars based on the Delta a-criterion were found at bluercolours. Towards the red side the fraction of CP2 stars drops to about3% for positive values of B-V or b-y with red limits roughlycorresponding to normal stars of spectral type A5. The photometricbehaviour of other peculiar stars: Am, HgMn, delta Del, lambda Boo, Heabnormal stars, as well as Be/shell stars and supergiants shows someslight, but definite deviations from normal stars. Spectroscopic andvisual binaries are not distinguished from normal stars in their Delta abehaviour. The results of this work justify larger statistical work(e.g. in open clusters) employing more time-saving photometric methods(CCD). \newpage Based on observations obtained at the European SouthernObservatory, La Silla, Chile. This research has made use of the Simbaddatabase, operated at CDS, Strasbourg, France. Table 2 is only availablein electronic form via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| The Angular Momentum of Main Sequence Stars and Its Relation to Stellar Activity
Rotational velocities are reported for intermediate-mass main sequencestars it the field. The measurements are based on new, high S/N CCDspectra from the Coudé Feed Telescope of the Kitt Peak NationalObservatory. We analyze these rotation rates for a dependence on bothmass and age. We compare the average rotation speeds of the field starswith mean velocities for young stars in Orion, the Alpha Persei cluster,the Pleiades, and the Hyades. The average rotation speeds of stars moremassive than $\sim1.6$ \msun\experience little or no change during theevolutionary lifetimes of these stars on the zero age main sequence orwithin the main sequence band. Less massive stars in the range betwee n1.6\msun\ and 1.3\msun\ also show little decline in mean rotation ratewhile they are on the main sequence, and at most a factor of 2 decreasein velocity as they evolve off the main sequence. The {\it e}-foldingtime for the loss of angular momentum b y the latter group of stars isat least 1--2 billion years. This inferred characteristic time scale forspindown is far longer than the established rotational braking time forsolar-type stars with masses below $\sim1.3$ \msun. We conclude from acomparison of the trends in rotation with trends in chromospheric andcoronal activity that the overall decline in mean rotation speed alongthe main sequence, from $\sim2$ \msun\ down to $\sim1.3$ \msun, isimposed during the pre-main sequence phase of evolution, and that thispattern changes little thereafter while the star resides on the mainsequence. The magnetic activity implicated in the rotational spindown ofthe Sun and of similar stars during their main sequence lifetimes mus ttherefore play only a minor role in determining the rotation rates ofthe intermediate mass stars, either because a solar-like dynamo is weakor absent, or else the geometry of the magnetic field is appreciablyless effective in removing angular momentu m from these stars. (SECTION:Stars)
| A Holistic View of the Magnetic Field in the Eridanus/Orion Region
We present observations of 21 cm emission-line Zeeman splitting at 217positions in the Orion/Eridanus loop region and incorporate them withstellar polarization data in a partially successful attempt to develop aholistic interpretation of the magnetic field structure on small andlarge size scales. We develop the "paraboloidal model" to describe theidealized perturbation to ambient magnetic field lines expected for aworm/chimney structure. We compare the magnetic field data to this modeland find fair agreement for part of the region. On the small scale ofone of the molecular clouds, previous interpretations invoke a helicalfield; in contrast, our interpretation invokes the Eridanus shock andits interaction with dense molecular clouds, in which the observedreversal in the line-of-sight field occurs naturally.
| The Hα behavior in bright giant stars.
We report high resolution spectroscopic observations of the Hαline profile for a sample of 32 bright giant stars with spectral typebetween F3II and G5II. By studying the link between the Hαbehavior and the stellar rotation in such class of luminosity we havefound no clear evidence that the rotational discontinuity establishedaround F9II is related with the Hα profiles. No emission features,neither time variations or asymmetries on the Hα line profileshave been detected for the bright giants analysed in the present work.
| X-Ray Morphology, Kinematics, and Geometry of the Eridanus Soft X-Ray Enhancement
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...453..256G&db_key=AST
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&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.
| Chromospheric Activity in Galactic Open Clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..157B&db_key=AST
| A photometric and spectroscopic search for luminous high latitude stars
Formulas, derived by Arellano Ferro and Mendoza in Paper I (1993), tocalculate Mv, log g, and (Fe/H) were applied to a group of 73A, F, and G stars of high galactic latitude previously classified assupergiant stars. The only star that showed, from data on hand, to beluminous, slightly iron deficient, and out of the galactic plane was BLTelescopii. The remainder of the sample either present controversialresults or are definitively giant or dwarf stars misclassified assupergiants. Thus, if luminous, young stars indeed exist out of thegalactic plane, they are extremely rare.
| The Hyades supercluster in the FK5
The members of the Hyades supercluster brighter than about M(V) = + 4mag and contained in the FK5, or having nearly FK5 quality propermotions, show a convergent point of (A,D) = (6h, + 6.5 deg). The Hyadescluster stars in the FK5 have a mean distance of 46.7 pc. Thesupercluster, as well as the Hyades and Praesepe cluster, populationsrepresent at least three age groups. Standard models indicate ages of 3to 4, 6, and 8 x 10 exp 8 yr, whereas model ages with convectiveovershoot are nearly twice this. Most of the Am and USPC stars in thesupercluster are of the same age. The Ap stars mark the onset of shellhydrogen burning. The photometry of the red giants confirms the agespread and indicates a weakening of CN strength with age. Attention iscalled to the need for further study of NGC 2423 as an effectiveprolusion to understanding the evolution of the supercluster.
| Photometry of F-K type bright giants and supergiants. I - Intermediate band and H-Beta observations
Over 1500 observations of 560 bright giants and supergiants of types F-Kare presented and compared to the observations by Gray and Olsen (1991).The present results include intermediate-band which is slightlydifferent from the Stromgren data by Gray and Olsen due to a differentwidth for the v filter. A systematic difference in m(1) - M(1) withdecreasing temperature is noted in the two H-Beta data sets, and thecorrelations are defined.
| Photometry of F-K type bright giant and supergiants. II - Calibration on indices in terms of luminosity reddening and abundance of F-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991AJ....102.1826E&db_key=AST
| An uvby-beta catalogue of F0-K0 supergiant stars brighter than V = 6.5
Photoelectric uvby-beta photometry is reported for 111 F0-K0 supergiantstars which are brighter than V = 6.5 mag and located betweendeclination of -15 and +61 deg. A comparison with previous observationsis made. A few stars which are suspected to present light variations arementioned.
| Six centimetre VLA radio survey of compact planetary nebulae
The results are presented of a radio continuum survey of 174 objectsclassified as possible or true planetary nebulae (Acker et al, 1983).Intensity contour plots, radio flux densities at 5 GHz, diameters, andaccurate positions are presented for the detected objects. Many of thedetected sources have high radio surface brightness temperaturesindicative of young planetary nebulae. Also, for each of the programsources, the IRAS Point Source Catalog is used to extract the fourphotometric flux densities and derive the total infrared flux, a dusttemperature, and the infrared excess.
| Starbursts, binary stars, and blue stragglers in local superclusters and groups. I - The very young disk and young disk populations
The distributions in the HR diagram with theoretical time-constant locifor stars in several young clusters and superclusters are compared todemonstrate that 'blue stragglers' in these aggregates are mostfrequently simply single massive (mode B) stars formed in bursts of starformation that occur at discrete intervals in time following theformation of the bulk of the low-mass (mode A) stars in the aggregate.The characteristics of the close binary systems in these aggregates areexamined to show that, in several cases, mass transfer by Roche lobeoverflow has or will occur and that, in some instances, the system wouldhave appeared as a blue straggler prior to the mass-transfer event, and,in other instances, mass transfer will lead to the identification of thesystem as a blue straggler. Thus, it is concluded that the bluestraggler phenomenon has at least two distinct physical origins: it mayoriginate from delayed formation (starbursts) or from 'delayedevolution' in some close binaries (mass transfer from an evolvedprimary).
| A systematic search for members of the Hyades Supercluster. IV - The metallic-line stars and ultrashort-period Cepheids
Bright Star Catalog stars with beta values in the 2.70-2.88 rangecontain 127 members of the Hyades Supercluster, which have been chosenon the basis of the direction of their proper motion. Available radialvelocities confirm supercluster membership for most of these stars.Exceptional regularity is noted in the values of the pulsation constantQ computed for the ultrashort period Cepheids on the basis of knownperiods, model masses and model radii. Outside the center of the Hyadescluster, the largest concentration of supercluster stars is in a regionof 30 pc radius, between 60 and 80 pc above the sun, where 30 percent ofthe expected stars in the temperature range presently discussed aresupercluster members.
| Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
| Prediction of spectral classification from photometric observations-application to the UVBY beta photometry and the MK spectral classification. I - Prediction assuming a luminosity class
An algorithm based on multiple stepwise and isotonic regressions isdeveloped for the prediction of spectral classification from photometricdata. The prediction assumes a luminosity class with reference touvbybeta photometry and the MK spectral classification. The precisionattained is about 90 percent and 80 percent probability of being withinone spectral subtype respectively for luminosity groups I and V and forluminosity groups III and IV. A list of stars for which discrepanciesappear between photometry and spectral classification is given.
| Spectral classification of the bright F stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88...95C&db_key=AST
| Spectra of Some Peculiar and Luminous Bright Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..314C&db_key=AST
| A Search for AP Stars with Very Long Periods
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..141W&db_key=AST
| Four-colour and H BET photometry of some bright southern stars- II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972MNRAS.160..155S&db_key=AST
| Rotation of evolving A and F stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....18..428D&db_key=AST
| Luminosities and Motions of the F-Type Stars. I. Luminosity and Metal Abundance Indices for Disk Population Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..741E&db_key=AST
| UBV and narrow-band UVBY photometry of bright stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73...84B&db_key=AST
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | エリダヌス座 |
| Right ascension: | 03h41m13.80s |
| Declination: | -11°48'11.0" |
| Apparent magnitude: | 6.49 |
| Distance: | 91.912 parsecs |
| Proper motion RA: | 80 |
| Proper motion Dec: | 33.3 |
| B-T magnitude: | 6.915 |
| V-T magnitude: | 6.529 |
Catalogs and designations:
|
