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The N2K Consortium. VII. Atmospheric Parameters of 1907 Metal-rich Stars: Finding Planet-Search Targets
We report high-precision atmospheric parameters for 1907 stars in theN2K low-resolution spectroscopic survey, designed to identify metal-richFGK dwarfs likely to harbor detectable planets. Of these stars, 284 arein the ideal temperature range for planet searches,Teff<=6000 K, and have a 10% or greater probability ofhosting planets based on their metallicities. The stars in thelow-resolution spectroscopic survey should eventually yield >60 newplanets, including 8-9 hot Jupiters. Short-period planets have alreadybeen discovered orbiting the survey targets HIP 14810 and HD 149143.
| 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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Detailed Analysis of Nearby Bulgelike Dwarf Stars. III. α-Element and Heavy-Element Abundances
The present sample of nearby bulgelike dwarf stars has kinematics andmetallicities characteristic of a probable inner disk or bulge origin.Ages derived by using isochrones give 10-11 Gyr for these stars, andmetallicities are in the range -0.80<=[Fe/H]<=+0.40. We calculatestellar parameters from spectroscopic data, and chemical abundances ofMg, Si, Ca, Ti, La, Ba, Y, Zr, and Eu are derived by using spectrumsynthesis. We found that [α-elements/Fe] show different patterns,depending on the element. Si/Fe, Ca/Fe, and Ti/Fe ratios declinesmoothly for increasing metallicities and essentially follow the diskpattern. O and Mg, products of massive supernovae, and also ther-process element Eu are overabundant relative to disk stars, showing asteeper decline for metallicities [Fe/H]>-0.3 dex, and[s-elements/Fe] roughly track the solar values, with no apparent trendwith metallicity for [Fe/H]<0, showing subsolar values for the metalrich stars. Both kinematical and chemical properties of the bulgelikestars indicate a distinct identity of this population when compared withdisk stars.
| 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.
| 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.
| Detailed Analysis of Nearby Bulgelike Dwarf Stars. II. Lithium Abundances
Li abundances are derived for a sample of bulgelike stars withisochronal ages of 10-11 Gyr. These stars have orbits with pericentricdistances, Rp, as small as 2-3 kpc and Zmax<1kpc. The sample comprises G and K dwarf stars in the metallicity range-0.80<=[Fe/H]<=+0.40. Few data on Li abundances in old turnoffstars (>=4.5 Gyr) within the present metallicity range are available.M67 (4.7 Gyr) and NGC 188 (6 Gyr) are the oldest studied metal-rich openclusters with late-type stars. Li abundances have also been studied fora few samples of old metal-rich field stars. In the present work, a highdispersion in Li abundances is found for bulgelike stars with allmetallicity ranges, comparable with values in M67. The role ofmetallicity and age on a Li depletion pattern is discussed. The possibleconnection between Li depletion and oxygen abundance due to atmosphericopacity effects is investigated.
| Detailed Analysis of Nearby Bulgelike Dwarf Stars. I. Stellar Parameters, Kinematics, and Oxygen Abundances
High-resolution échelle spectra were obtained with the Fiber-fedExtended Range Optical Spectrograph at the 1.5 m ESO telescope for 35nearby bulgelike stars with metallicities in the range-0.8<=[Fe/H]<=+0.4. Geneva photometry, astrometric data fromHipparcos, and radial velocities from CORAVEL are available for thesestars. From Hipparcos data, it appears that the turnoff of thispopulation indicates an age of 10-11 Gyr (as stated by Grenon in 1999).Detailed analysis of the sample stars is carried out, and atmosphericparameters derived from spectroscopic and photometric determinations arepresented. Oxygen abundances are derived based on the forbidden [O I]6300.3 Å line. The results show an oxygen overabundance patternfor most of the sample stars when compared to their disk counterparts.Based on observations carried out at the European Southern Observatory,La Silla.
| Oxygen Abundances in Bulge-like Dwarf Stars
High resolution échelle spectra were obtained with the FEROSspectrograph at the 1.5m ESO telescope for 35 nearby bulge-like stars.From Hipparcos data it appears that the turn-off of this populationindicates an age of 10--11 Gyr (Grenon 2000). Oxygen abundances arecalculated using the [O I] line at 6300.3 Å. The derived resultsshow an oxygen overabundance for most of our sample stars when comparedto their disk counterparts.
| 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.
| 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.
| UVBY - beta photometry of high-velocity and metal-poor stars. VI - A second catalogue, and stellar populations of the Galaxy
A second catalog of uvby-beta photometry for 553 high-velocity stars ispresented. Combining the catalogs, reliable (Fe/H) values are obtainedfor 1214 stars and reliable kinematic parameters for 1149. The totalsample contains at least three significant, distinct stellar populationswith properties very similar to those given in the literature of the oldthin disk, thick disk, and halo. The thick-disk component has mean(Fe/H) about -0.50 +/- 0.10 dex and sigma(Fe/H) about 0.25 +/- 0.03 dex,but there is evidence for a significant thick-disk contribution down to(Fe/H) about -1.4. A diagonal cut in the V(rot), (Fe/H) diagramindicates that there is not a chemical gradient in the Galactic halo.The mean V(rot), mean (Fe/H) curve for the whole sample indicates thatthe halo evolved mostly independently of the disk.
| UBV photometry of HD stars in the fields of selected cataclysmic variables.
Not Available
| 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.
| 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.
| Lowell proper motions II : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory
Not Available
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Водолей |
| Прямое восхождение: | 22h19m07.77s |
| Склонение: | -07°18'49.0" |
| Видимая звёздная величина: | 8.87 |
| Расстояние: | 84.89 парсек |
| Собственное движение RA: | 230.3 |
| Собственное движение Dec: | -144.8 |
| B-T magnitude: | 9.613 |
| V-T magnitude: | 8.932 |
Каталоги и обозначения:
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