Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes
We present a method which separates field dwarfs and field giants bytheir 2MASS and V apparent magnitudes. This method is based onspectroscopically selected standards and is hence reliable. We appliedit to stars in two fields, SA 54 and SA 82, and we estimated a full setof Galactic model parameters for giants including their total localspace density. Our results are in agreement with the ones given in therecent literature.
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Fine structure in the phase space distribution of nearby subdwarfs
We analysed the fine structure of the phase space distribution functionof nearby subdwarfs using data extracted from various catalogues.Applying a new search strategy based on Dekker's theory of galacticorbits, we found four overdensely populated regions in phase space.Three of them were correlated with previously known star streams: theHyades-Pleiades and Hercules streams in the thin disk of the Milky Wayand the Arcturus stream in the thick disk. In addition we find evidencefor another stream in the thick disk, which resembles closely theArcturus stream and probably has the same extragalactic origin.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| 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
| A Survey of Proper-Motion Stars. XVI. Orbital Solutions for 171 Single-lined Spectroscopic Binaries
We report 25,563 radial velocity measurements for 1359 single-linedstars in the Carney-Latham sample of 1464 stars selected for high propermotion. For 171 of these, we present spectroscopic orbital solutions. Wefind no obvious difference between the binary characteristics in thehalo and the disk populations. The observed frequency is the same, andthe period distributions are consistent with the hypothesis that the twosets of binaries were drawn from the same parent population. Thissuggests that metallicity in general, and radiative opacities inparticular, have little influence over the fragmentation process thatleads to short-period binaries. All the binaries with periods shorterthan 10 days have nearly circular orbits, while the binaries withperiods longer than 20 days exhibit a wide range of eccentricities and amedian value of 0.37. For the metal-poor high-velocity halo binaries inour sample, the transition from circular to eccentric orbits appears tooccur at about 20 days, supporting the conclusion that tidalcircularization on the main sequence is important for the oldestbinaries in the Galaxy. Some of the results presented here usedobservations made with the Multiple Mirror Telescope, a joint facilityof the Smithsonian Institution and the University of Arizona.
| 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
| The Age of the Inner Halo Globular Cluster NGC 6652
Hubble Space Telescope (V, I) photometry has been obtained for the innerhalo globular cluster NGC 6652. The photometry reaches ~4 mag below theturnoff and includes a well-populated horizontal branch. This cluster islocated close to the Galactic center, at RGC~=2.0 kpc, with areddening of E(V-I)=0.15+/-0.02, and has a metallicity of [Fe/H]~=-0.85.Based upon ΔVSGBHB, NGC 6652 is 11.7+/-1.6Gyr old. Using ΔVSGBHB, precise differentialages for 47 Tuc (a thick disk globular cluster), M107, and NGC 1851(both halo clusters) were obtained. NGC 6652 appears to be the same ageas 47 Tuc and NGC 1851 (within +/-1.2 Gyr), while there is a slightsuggestion that M107 is older than NGC 6652 by 2.3+/-1.5 Gyr. As this isa less than 2 σ result, this issue needs to be investigatedfurther before a definitive statement regarding the relative age of M107and NGC 6652 may be made. Based on observations made with the NASA/ESAHubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
| Homogeneous photometry and metal abundances for a large sample of Hipparcos metal-poor stars*
Homogeneous photometric data (Johnson V, B-V, V-K, Cousins V-I andStrömgren b-y), radial velocities, and abundances of Fe, O, Mg, Si,Ca, Ti, Cr and Ni are presented for 99 stars with high-precisionparallaxes measured by the Hipparcos satellite. These data have beenpreviously used to assist the derivation of accurate distances and agesof Galactic globular clusters. Magnitudes and colours for the programmestars were obtained by combining and standardizing carefully selectedliterature data available in the Simbad data base, and V and B-V valuesmeasured by the Hipparcos/Tycho mission. Comparison of colours for ourtargets suggests: (i) ground-based and Tycho B-V values agree well forcolours bluer than 0.75 mag, but have a lot of scatter for reddercolours; (ii) the Hipparcos V-I colours have a very large scatter and azero-point offset of +0.02 mag compared to the literature values.The programme stars have metal abundances in the range-2.5<[Fe/H]<0.2. The spectroscopic observational data set consistsof high-dispersion (15 000200) spectraobtained at the Asiago and McDonald Observatories for 66 stars. Theanalysis is carried out following the same precepts as those used inprevious papers of this series, and includes corrections for departuresfrom LTE in the formation of the O lines. The main results are: (i) theequilibrium of ionization of Fe is well satisfied in late F-early Kdwarfs; (ii) oxygen and α-elements are overabundant by ~0.3 dex.This large homogeneous abundance data set has been used to recalibratethe abundance scales of Schuster & Nissen, Ryan & Norris andCarney et al. (1994).
| Photoelectric Vilnius Photometry of Hipparcos Turn-Off Region Stars
Seven-color photometry in the Vilnius system and photometricclassification in terms of spectral type, absolute magnitude andmetallicity are presented for 145 Hipparcos stars of the turn-offregion, most of which have parallaxes determined to an accuracy of atleast 15%. The stars selected for the observing program included thoseidentified kinematically as intermediate between the thin disk and halo,plus a number of weak-lined stars discovered previously from objectiveprism surveys. The metallicity distribution we find for a kinematicallydefined sample of possible members of the thick disk has a meanabundance [Fe/H]= --0.3 dex and a dispersion of 0.3 dex. Our data seemto suggest a large age for this intermediate population.
| Rubidium in Metal-deficient Disk and Halo Stars
We report the first extensive study of stellar Rb abundances.High-resolution spectra have been used to determine, or set upper limitson, the abundances of this heavy element and the associated elements Y,Zr, and Ba in 44 dwarfs and giants with metallicities spanning the range-2.0<[Fe/H]<0.0. In metal-deficient stars Rb is systematicallyoverabundant relative to Fe; we find an average [Rb/Fe] of +0.21 for the32 stars with [Fe/H]<-0.5 and measured Rb. This behavior contrastswith that of Y, Zr, and Ba, which, with the exception of three new CHstars (HD 23439A and B and BD +5 deg3640), are consistently slightlydeficient relative to Fe in the same stars; excluding the three CHstars, we find that the stars with [Fe/H]<-0.5 have average [Y/Fe],[Zr/Fe], and [Ba/Fe] of -0.19 (24 stars), -0.12 (28 stars), and -0.06(29 stars), respectively. The different behavior of Rb on the one handand Y, Zr, and Ba on the other can be attributed in part to the factthat in the Sun and in these stars Rb has a large r-process componentwhile Y, Zr, and Ba are mostly s-process elements with only smallr-process components. In addition, the Rb s-process abundance isdependent on the neutron density at the s-processing site. Publishedobservations of Rb in s-process enriched red giants indicate a higherneutron density in the metal-poor giants. These observations imply ahigher s-process abundance for Rb in metal-poor stars. The calculatedcombination of the Rb r-process abundance, as estimated for the stellarEu abundances, and the s-process abundance, as estimated for red giants,accounts satisfactorily for the observed run of [Rb/Fe] with [Fe/H].
| Ages of Globular Clusters from HIPPARCOS Parallaxes of Local Subdwarfs
We report here initial but strongly conclusive results for absolute agesof Galactic globular clusters (GGCs). This study is based onhigh-precision trigonometric parallaxes from the HIPPARCOS satellitecoupled with accurate metal abundances ([Fe/H], [O/Fe], and [ alpha/Fe]) from high-resolution spectroscopy for a sample of about thirtysubdwarfs. Systematic effects due to star selection (Lutz-Kelkercorrections to parallaxes) and the possible presence of undetectedbinaries in the sample of bona fide single stars are examined, andappropriate corrections are estimated. They are found to be small forour sample. The new data allow us to reliably define the absolutelocation of the main sequence (MS) as a function of metallicity. Theseresults are then used to derive distances and ages for a carefullyselected sample of nine globular clusters having metallicitiesdetermined from high-dispersion spectra of individual giants accordingto a procedure totally consistent with that used for the fieldsubdwarfs. Very precise and homogeneous reddening values have also beenindependently determined for these clusters. Random errors for ourdistance moduli are +/-0.08 mag, and systematic errors are likely of thesame order of magnitude. These very accurate distances allow us toderive ages with internal errors of ~12% (+/-1.5 Gyr). The main resultsare: 1. HIPPARCOS parallaxes are smaller than corresponding ground-basedmeasurements, leading, in turn, to longer distance moduli (~0.2 mag) andyounger ages (~2.8 Gyr). 2. The distance to NGC 6752 derived from our MSfitting is consistent with that determined using the white dwarf coolingsequence. 3. The relation between the zero-age HB (ZAHB) absolutemagnitude and metallicity for the nine program clusters isMV({ZAHB})=(0.22+/-0.09)([{Fe}/{H}]+1.5)+(0.49+/-0.04) . Thisrelation is fairly consistent with some of the most recent theoreticalmodels. Within quoted errors, the slope is in agreement with that givenby the Baade-Wesselink (BW) analysis of RR Lyrae stars by Fernley andClementini et al., while it is somewhat shallower than the relationgiven by Sandage. The zero-point is 0.2 to 0.3 mag brighter than thatobtained with BW, while it agrees fairly well with that given bySandage. A comparison with alternative relationships is brieflydiscussed. 4. The corresponding LMC distance modulus is (m - M)0 = 18.60+/- 0.07, in good agreement with the recent values of 18.70 +/- 0.10 and18.54 +/- 0.2 derived by Feast & Catchpole and van Leeuwen et al.,respectively, from HIPPARCOS parallaxes of Galactic Cepheid and Miravariables. 5. The age of the bona fide old globular clusters (OosterhoffII and BHB), based on the absolute magnitude of the turnoff (atheoretically robust indicator) is {Age}=11.8^{+2.1}_{-2.5} {Gyr} ,wherethe error bar is the 95% confidence range. The rms scatter of individualages around the mean value is ~10%, in agreement with expectations fromobservational errors alone (that is, we do not find it necessary tointroduce a real age scatter among these clusters). A reliable study ofthe relative ages requires the use of age indicators better suited tothis purpose and data for a larger sample of GGCs. 6. Allowing for aminimum delay of 0.5 Gyr from the birth of the universe until theformation of globular clusters, our age estimate is compatible with anEinstein-de Sitter model if H0 <= 64 km s-1 Mpc-1, or H0 <= 83 kms-1 Mpc-1 in a flat universe with Omega m = 0.2. Since these upperlimits are well within the confidence range of most determinations ofH0, we conclude that the present age of globular clusters does notconflict with standard inflationary models of the universe.
| A survey of proper motion stars. 12: an expanded sample
We report new photometry and radial velocities for almost 500 stars fromthe Lowell Proper Motion Catalog. We combine these results with ourprior sample and rederive stellar temperatures based on the photometry,reddening, metallicities (using chi squared matching of our 22,500 lowSignal to Noise (S/N) high resolution echelle spectra with a grid ofsynthetic spectra), distances, space motions, and Galactic orbitalparameters for 1269 (kinematics) and 1261 (metallicity) of the 1464stars in the complete survey. The frequency of spectroscopic binariesfor the metal-poor ((m/H) less than or equal to -1.2) stars with periodsshorter than 3000 days is at least 15%. The spectroscopic binaryfrequency for metal-rich stars ((m/H) greater than -0.5) appears to belower, about 9%, but this may be a selection effect. We also discussspecial classes of stars, including treatment of the double-linedspectroscopic binaries, and identification of subgiants. Four possiblenew members of the class of field blue stragglers are noted. We pointout the detection of three possible new white dwarfs, six broad-lined(binary) systems, and discuss briefly the three already knownnitrogen-rich halo dwarfs. The primary result of this paper will beavailable on CD-ROM, in the form of a much larger table.
| First giant branch and asymptotic giant branch stars in nearby aggregates
The properties of the brightest red stars in several aggregates in theGalaxy are compared with theoretical models. 22 asymptotic giant branch(AGB) stars are identified, four of which are in the thermally pulsingAGB (TPAGB) phase and four of which are TPAGB carbon stars. Also, fourcases of RGB stars are identified which have accreted substantial massfrom the carbon-rich TPAGB precursor of a current white dwarf companion.There is general agreement between the observed and theoretical slopesof the RGB and early AGB branches, and quantitative differences betweenthe positioning of observed sequences can be understood in terms ofdifferences in metallicity and mass predicted by the theory.
| Starbursts, blue stragglers, and binary stars in local superclusters and groups. II - The old disk and halo populations
A study of the distribution in the HR diagram of stars in severalold-disk population aggregates and in several halo-population aggregatesindicates that the blue straggler phenomenon is ubiquitous. In all thecases considered, several stars are found to lie far from the locusdefined by a semiempirical isochrone that best fits the distribution ofthe bulk of the stars in the aggregate. The results support thestarburst interpretation of blue stragglers in young-disk aggregates.
| Four-color UVBY and H-beta photometry of high-velocity and metal-poor stars. I - The catalogue of observations
A catalog of four-color uvby and H-beta photometry for 711 high-velocityand metal-poor stars is given. The selection of the stars and theobserving and reduction techniques used to obtain these data arediscussed. The photometry has been transformed closely onto the standarduvby-beta system. The errors of the data have been estimated using bothinternal and external comparisons. The data are uniform over the sky;that is, there are no significant north-south differences. For the largemajority of stars the mean errors of V, m1, c1, and beta are less than +or - 0.008 mag, and the error of b-y is less than + or - 0.005 mag.Values of V, b-y and beta and rough photometric classifications aregiven for 63 red and/or evolved stars that fall outside the range of thephotometric transformations.
| New subdwarfs. VI - Kinematics of 1125 high-proper-motion stars and the collapse of the Galaxy
The UVW velocity components, planar eccentricities, and angular momentaof 878 high-proper-motion stars are determined using the radial-velocitydata of Fouts and Sandage (1986) and compared with chemical abundancesand photometric parallaxes from the UBV photometry of Sandage and Kowal(1986). The results are presented, along with published data on 247additional stars, in extensive tables and graphs and characterized indetail. Two approximately equal components are differentiated: alow-velocity component identified as part of the thick disk described byGilmore and Reid (1983) and a high-velocity halo component. The data arefound to support a model of Galactic collapse (with concomitant spinupand progressive chemical enrichment) which includes a rotating bulge(the thick disk) with kinematic and metallicity properties between thoseof the old thin disk and the halo.
| Population studies. II - Kinematics as a function of abundance and galactocentric position for (Fe/H) of -0.6 or less
A catalog is presented of some 1200 Galactic objects which have radialvelocities and (Fe/H) abundances of -0.6 or less. These data areanalyzed to yield information on the kinematic properties of the olderpopulations of the Galaxy and on the interdependence between kinematicsand abundance. It is found that the kinematics of the availablekinematically selected stars differ from those of the nonkinematicallyselected objects. No evidence is found for any significant difference inthe kinematic properties of the various halo subgroups, nor for anydependence of kinematics on abundance. While the rotation of the halo issmall at about 37 km/s for (Fe/H) of -1.2 or less, it rises quickly forhigher abundances to a value of about 160 km/s at (Fe/H) = 0.6. Objectsin the abundance range -0.9 to -0.6 appear to belong predominantly to apopulation possessing the kinematic characteristics of a thick disk. Theimplications of these findings for the suggestion that globular clustersbelong to the same population as the noncluster objects, for the originof the thick disk, and for the mass of the Galaxy are discussed.
| New subdwarfs. V - Radial velocities for 889 high-proper-motion stars measured with the Mount Wilson 100 inch reflector
New radial velocities have been obtained from 2265 measurements of 889high-proper-motion stars taken from the subdwarf candidate list of aprevious paper. The observations were made with the Mount Wilson 100 inHooker reflector coude spectrograph with a Reticon detector, giving aninternal error of a single measurement of 4.7 km/s. From 88 stars incommon with previously known subdwarfs; the external error of the datais 6.9 km/s per measurement, and the velocity system is shown to be onthe system of the Wilson General Catalog to better than 1 km/s. Of the878 stars with nonvariable velocities in the sample, 38 have radialvelocities larger than 200 km/s, of which 22 are new. There is acorrelation between radial velocity and reduced ultraviolet excess asexpected from the previously known relations between space motion andchemical composition. The Stroemberg asymmetric drift is directlyvisible in the radial velocity and the proper-motion data separately aseach is displayed as a function of galactic longitude.
| New subdwarfs. IV - UBV photometry of 1690 high-proper-motion stars
A photometric list of 1690 stars of known high proper motion is used tosearch for potential high-velocity stars of various metallicity valuesin order to find candidates for trigonometric programs on subdwarfs andto enlarge the sample with which to study the relation between stellarkinematics and metal abundance. A list of 113 stars with tangentialspace velocities of 300 km/s or greater is obtained, the highesttangential velocity relative to the sun being 630 km/s. By using thevariation of the tangential velocity with longitude and adopting thegalactic rotation at the solar circle to be 220 km/s, the rotation ofthe subdwarf system is estimated at 0 + or - 50 km/s from the transversevelocity alone, in agreement with determinations based on other methods.
| G. P. Kuiper's spectral classifications of proper-motion stars
Spectral classifications are listed for over 3200 stars, mainly of largeproper motion, observed and classified by Kuiper during the years1937-1944 at the Yerkes and McDonald Observatories. While Kuiper himselfpublished many of his types, and while improved classifications are nowavailable for many of these stars, much of value remains. For many ofthe objects, no other spectral data exist.
| Calibrations of the reddening, luminosity, and abundance of old disk giants from photometry of stars in M67, NGC 3680, NGC 2420, and the Wolf 630 and Arcturus groups
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983AJ.....88..813E&db_key=AST
| A photometric search for halo binaries. I - New observatinal data. II - Results
Carney (1982) has reported JHK photometry for 76 Hyades dwarfs. Inconnection with the present investigation, results of similarobservations of field halo stars are provided along with some uvbyphotometry. In addition, older spectrophotometric and photometric dataused previously for temperature determinations have been collected. Theinfrared and uvby data were obtained primarily with the objective ofidentifying binaries with dissimilar components among a sample of fieldhalo dwarfs by comparing metallicity insensitive blue and infraredcolors. Attention is given to 111 spectrophotometric scans of 89 stars,67 uvby measures of 41 stars, 127 UBV measures of 87 stars, 147 (RI)Jmeasures of 127 stars, 8 JHK measures of eight stars in the 'HCO'system, and 212 JHK measures of 137 stars in the 'CIT' system. Themajority of these stars are dwarfs, and most of them are metal poor. Theresults of a search for binaries in 71 halo dwarf stars are alsopresented, taking into account a few other dwarfs of special interest.
| Intermediate-band photometry of late-type stars. VIII - Nonvariable stars in the halo population near the sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979ApJ...229..158E&db_key=AST
| Intermediate-band photometry of late-type stars. V - Calibration of indices
Additional data for several stellar groups and clusters are used toimprove a previously determined provisional relation betweenM1 photometric index and the parameter /Fe/H/(solar) as wellas to test the usefulness of the C1 photometric index forluminosity determinations. The data are for 43 members of the Wolf 630group, 14 members of the 61 Cygni group, 30 members of the Arcturusgroup, 14 members of Kapteyn's star groups, and various members of theHyades, 47 Tuc, NGC2420, Omega Cen, and an anonymous group of subdwarfs.It is found that in general the values of C1 only confirm agiant or dwarf classification without yielding accurate luminosities andthat the main contribution of C1 for disk objects is inisolating peculiar stars. The results also indicate that there is aluminosity effect in M1 for the strongest-lined stars andthat the values of M1 become distorted, probably by thepresence of TiO, for R-I larger than about +0.5 magnitude. An array forinterpolating /FE/H/(solar) from (R-I, M1) is constructed byadopting mean values of /Fe/H/(solar) equal to +0.1,-0.35, -0.6, and-1.8 for the Hyades, Wolf 630, Arcturus, and Kapteyn's star groups,respectively.
| Intermediate band photometry of late-type stars. II - Some stellar groups
Observations on the (R, I) system and a modified Stromgren system ofmembers of six stellar groups are used to demonstrate the chemicalhomogeneity of some 70% or 80% of the members assigned to the groups onthe basis of kinematics. The groups discussed are the Hyades, Wolf 630,Arcturus, Groombridge 1830, and Kapteyn's Star Groups as well as ananonymous group of a half dozen subdwarfs with (U, V) near (-150, -320)km/s. Standards for a previously described photometric system areextended, and additional F- and G-type standards for the (R, I) systemare presented. A simple relation is derived for computing the Fe/Habundance ratio for most stars in the corrected (R-I) interval from +0.2to +0.45 magnitude.
| Intermediate-band photometry of late-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..732E&db_key=AST
| The oldest disk stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..162E&db_key=AST
| New subdwarfs. II. Radial velocities, photometry, and preliminary space motions for 112 stars with large proper motion
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...158.1115S&db_key=AST
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Aquarius |
| Ascensió Recta: | 22h50m45.94s |
| Declinació: | +01°51'54.6" |
| Magnitud Aparent: | 9.334 |
| Moviment propi RA: | 100.4 |
| Moviment propi Dec: | -383.3 |
| B-T magnitude: | 10.123 |
| V-T magnitude: | 9.4 |
Catàlegs i designacions:
|
