내용
사진
사진 업로드
DSS Images Other Images
관련 글
Lithium abundances for early F stars: new observational constraints for the Li dilution
Aims.To investigate any correlation between Li abundances and rotationalvelocities among F-G evolved stars, we study a large sample of early Fstars from the Bright Star Catalogue (BSC), most of them classified inthe literature as giant stars.Methods.Physical parameters and Liabundances are estimated for each star, often for the first time, bycomparing observed and synthetic spectra. We analyse the position of thestars in the H-R Diagram based on Hipparcos data using stellarevolutionary tracks and we discuss their Li abundances and projectedrotational velocities.Results.Observed stars are mostly on theturnoff, with masses between 1.5 and 2.0 Mȯ. The starswith measured A(Li) abundance show high Li content, most of them withabundance near the cosmic value. The A(Li) versus V sin i diagram showsthe same trend as reported in previous studies: fast rotators (V sinigse 30 km s-1) are also stars with high Li content, whereasslow rotators present a wide range of values of A(Li), ranging from nodetected Li to the cosmic value.
| 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
| High resolution spectroscopy over lambda lambda 8500-8750 Å for GAIA. IV. Extending the cool MK stars sample
A library of high resolution spectra of MK standard and reference stars,observed in support to the GAIA mission, is presented. The aim of thispaper is to integrate the MK mapping of Paper I of this series as wellas to consider stars over a wider range of metallicities. Radialvelocities are measured for all the target stars.The spectra are available in electronic form (ASCII format) at CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/406/995 and from the webpage http://ulisse.pd.astro.it/MoreMK/, where further bibliographicalinformation for the target stars is given.
| 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
| HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
We derive age-metallicity relations (AMRs) and orbital parameters forthe 1658 solar neighbourhood stars to which accurate distances aremeasured by the HIPPARCOS satellite. The sample stars comprise 1382 thindisc stars, 229 thick disc stars, and 47 halo stars according to theirorbital parameters. We find a considerable scatter for thin disc AMRalong the one-zone Galactic chemical evolution (GCE) model. Orbits andmetallicities of thin disc stars show now clear relation each other. Thescatter along the AMR exists even if the stars with the same orbits areselected. We examine simple extension of one-zone GCE models whichaccount for inhomogeneity in the effective yield and inhomogeneous starformation rate in the Galaxy. Both extensions of the one-zone GCE modelcannot account for the scatter in age - [Fe/H] - [Ca/Fe] relationsimultaneously. We conclude, therefore, that the scatter along the thindisc AMR is an essential feature in the formation and evolution of theGalaxy. The AMR for thick disc stars shows that the star formationterminated 8 Gyr ago in the thick disc. As already reported by Grattonet al. (\cite{Gratton_et.al.2000}) and Prochaska et al.(\cite{Prochaska_et.al.2000}), thick disc stars are more Ca-rich thanthin disc stars with the same [Fe/H]. We find that thick disc stars showa vertical abundance gradient. These three facts, the AMR, verticalgradient, and [Ca/Fe]-[Fe/H] relation, support monolithic collapseand/or accretion of satellite dwarf galaxies as likely thick discformation scenarios. Tables 2 and 3 are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http:/ /cdsweb.u-strasbg.fr/ cgi-bin/qcat?J/ A+A/394/927
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| On the Variability of F1-F9 Luminosity Class III-V Stars
Hipparcos Satellite photometry of F1-F9 luminosity class III-V starsindicates that most are not particularly variable. A few stars for whichfurther study is desirable are identified.
| The mass of X-ray Nova Scorpii1994 (=GRO J1655-40)
We have obtained high- and intermediate-resolution optical spectra ofthe black hole candidate Nova Scorpii 1994 in 1998 May/June, when thesource was in complete (X-ray) quiescence. We measure the radialvelocity curve of the secondary star and obtain a semi-amplitude ofK_2=215.5 +/- 2.4 km s^-1, which is 6 per cent lower than the onlypreviously determined value. This new value for K_2 thus reduces thebinary mass function to f(M) = 2.73 +/- 0.09 M_solar. Using only thehigh-resolution spectra, we constrain the rotational broadening of thesecondary star, v sin i, to lie in the range 82.9-94.9 km s^-1 (95 percent confidence) and thus constrain the binary mass ratio to lie in therange 0.337-0.436 (95 per cent confidence). We can also combine ourresults with published limits for the binary inclination to constrainthe mass of the compact object and secondary star to the ranges 5.5-7.9and 1.7-3.3 M_solar respectively (95 per cent confidence). Finally, wereport on the detection of the lithium resonance line at 6707.8 Å,with an equivalent width of 55 +/- 8 m Å.
| The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants
We present X-ray data for all late-type (A, F, G, K, M) giants andsupergiants (luminosity classes I to III-IV) listed in the Bright StarCatalogue that have been detected in the ROSAT all-sky survey.Altogether, our catalogue contains 450 entries of X-ray emitting evolvedlate-type stars, which corresponds to an average detection rate of about11.7 percent. The selection of the sample stars, the data analysis, thecriteria for an accepted match between star and X-ray source, and thedetermination of X-ray fluxes are described. Catalogue only available atCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Spectroscopic binary orbits from photoelectric radial velocities Paper 120: HR 3325
Not Available
| 9 Aurigae: strong evidence for non-radial pulsations
We present further photometric observations of the unusual F0 V star 9Aurigae and present evidence that this star's radial velocity,spectroscopic line widths and line depths are also variable with thesame frequencies as the photometric data (f_1~=0.795 and f_2~=0.345d^-1). The phases of these sinusoids are stable over time-scales oflonger than one year, though the amplitudes can vary, making theprediction of photometric behaviour impossible. Given that a variety ofother explanations have already been discounted (e.g. interactions witha close companion, the existence of a lumpy, orbiting ring of dust, orstar spots) and that these variations occur on time-scales an order ofmagnitude slower than the fundamental radial pulsation period, we havevery strong evidence that 9 Aurigae exhibits non-radial g-modepulsations. Since the power spectrum of the radial velocity data showsfrequency f_2 but does not clearly show f_1, the present data suggestthat f_2 is associated with a low-degree spherical harmonic L=1 or 2),while f_1 is associated with a higher degree harmonic. 9 Aurigae, alongwith such stars as gamma Doradus, HD 224638, HD 224945, and HD 164615,appears to constitute a new class of pulsating variables. These starsare to be found at or beyond the cool edge of the Cepheid instabilitystrip in the HR Diagram. Prior to this, only much hotter stars have beenshown to exhibit non-radial g-modes.
| 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
| Analyses of archival data for cool dwarfs. 2: A catalog of temperatures
A calibration presented in a previous paper is used in this paper toderive temperatures for FGK stars near the main sequence. Thecalibration is checked against published counterparts, and it is foundthat previous calibrations have not established K-dwarf temperatures inparticular beyond reasonable doubt. The database assembled to derive thetemperatures is described, and the problems posed by close binaries areevaluated. The newly derived temperatures are used to check a line-depthratio proposed as a thermometer by Gray and Johanson (1991, PASP, 103,439), and it is found that the ratio is metallicity-sensitive.Temperatures are given for a total of 417 stars.
| Silicon abundance in Population I giants
Silion to carbon abundance ratios for Population I giants weredetermined from emission lines originating in the transition layersbetween stellar chromospheres and coronae. For effective temperatureslarger than 6200 K we find a group of stars for which the silicon tocarbon abundance ratio appears to be increased. These stars arepresumably descendents from AP stars on Am stars with increased surfacesilicon to carbon abundance ratios. Around B-V approximately equal to0.45 this anomaly disappears as is to be expected due to the increaseddepth of the convection zone and therefore deeper mixing which dilutesthe surface overabundances. Unexplained is the apparent increasedsilicon to carbon abundance ratio observed for several stars cooler than5100 K. RS CVn and related stars do not show this increased abundanceratio.
| Early type high-velocity stars in the solar neighborhood. IV - Four-color and H-beta photometry
Results are presented from photometric obaservations in the Stromgrenuvby four-color and H-beta systems of early-type high-velocity stars inthe solar neighborhood. Several types of photometrically peculiar starsare selected on the basis of their Stromgren indices and areprovisionally identified as peculiar A stars, field horizontal-branchstars, metal-poor stars near the Population II and old-disk turnoffs,metal-poor blue stragglers, or metallic-line A stars. Numerousphotometrically normal stars were also found.
| Large and kinematically unbiased samples of G- and K-type stars. IV - Evolved stars of the old disk population
Modified Stromgren and (R,I) photometry, along with DDO and Genevaphotometry, are presented for a complete sample of evolved old-disk Gand K giants in the Bright Star Catalogue. Stars with ages of between1.5 x 10 to the 9th and 10 to the 10th yr are found to have anear-normal distribution of heavy element abundances, centered on anFe/H abundance ratio of -0.1 dex. The old disk clusters NGC 3680 and IC4651 contain red-straggler young-disk giants that are probablycontemporaries of the blue stragglers in the clusters.
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| Magnetic structure in cool stars. XV - The evolution of rotation rates and chromospheric activity of giants
For cool giants and subgiants the observed dependence of rotationalvelocity and Ca II H and K line-core emission on color B-V isinterpreted in terms of changes in the moment of inertia by stellarevolution. Modeling of the rotational velocity during the evolution ofcool giants with masses between 2.0 and 3.0 solar masses, by taking intoaccount the change in the moment of inertia and assuming rigid-bodyrotation and conservation of angular momentum, describes the observeddecrease of v sin i with B-V. The computed evolution of the rotationalvelocity, together with the empirical relation between the Ca IIline-core emission and the rotation rate, explain the observed drop inthe Ca II line-core emission for giants at B-V = about 0.95. Forsubgiants with masses of about 1.5 solar mass, the change in the momentof inertia by itself cannot explain the observed v sin i distribution:there are indications of loss of angular momentum, presumably bymagnetic braking.
| The intrinsic colour calibration of Stromgren photometry for F-type stars
Several calibrations of Stromgren uvby-beta photometry with respect tothe intrinsic color (b - y)0 exist for F-type stars. These calibrationsare complementary, since they are valid for different ranges ofheavy-element abundance. A new comprehensive intrinsic color calibrationis presented. It is valid for all F0-G2 stars of luminosity classesIII-V, except possibly the most extreme population II stars. Thecalibration is based on 1231 stars. The rms scatter around thecalibration is 0.009 mag (one star).
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
| Radial velocities of bright southern stars. V - 146 Population II F stars and related stars
This paper presents new radial velocity determinations, based on 20 A/mmcoude plates, for 146 southern stars brighter than m(v) = 8.3. Drawnfrom the catalog of uvby-beta photometry of southern A5-G0 stars byOlsen (1983), the program stars are certain or suspected Population IIstars. One triple-lined and 10 double-lined binaries have been detected,including HD 210737, for which a preliminary orbit has been derived.Notes on spectral peculiarities are given.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
| Intermediate band, H-beta, and RI photometry of a large sample of stars unbiased with respect to their motion. I - The F-type stars
Intermediate band and H-beta data from a sample of 1000 stars earlierthan type G2 are presented and discussed relative to the stars'luminosities, metal abundances, and motion. Two groups of stars areconsidered, one within 10 arcsec of the South Galactic Pole and 8.5-8.6mag stars contained in the Moore-Paddock (1950) and Wayman (1960)samples (MP-W). The MP-W stars are mainly old disk population stars withmetal abundances of 4-0.25 solar values. Possible age-abundancedistribution-luminosity connections are explored, as are techniques forseparating old and young disk population objects.
| Metal abundance and microturbulence in F0-G2 stars and the calibration of the Stromgren m1 index
The strengths of two narrow groups of metal lines are measuredphotoelectrically by means of an echelle spectrometer for 16 F0-G2 giantfield stars and for 12 Hyades main-sequence stars. A model-atmosphereanalysis of these observations and similar observations of main-sequencefield stars observed earlier results in the determination of the metalabundance for 179 stars. In addition, the microturbulence parameter isdetermined for 73 of these stars. The internal accuracy of the resultsis estimated to be plus or minus 0.08 for the logarithmicmetal-to-hydrogen ratio and plus or minus 0.2 km/sec for themicroturbulence parameter. The metal abundances are found to agree verysatisfactorily with values of the logarithmic iron-to-hydrogen ratiodetermined from classical coude spectroscopy regarding both zero pointand scale. It is found that the microturbulence parameter is a functionof the effective temperature and the surface gravity. It increases from1.2 km/sec for solar type stars to approximately 3.0 km/sec for earlyF-type giants.
| Study of the F-type 1 MK spectral types.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..637M&db_key=AST
| The Bibliographical Star Index
Not Available
| MK classifications for F-and G-type stars. 3.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..682H&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
| A catalogue of four-color photometry of late F-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74..705P&db_key=AST
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
INHABITED SKY
