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מאמרים קשורים
Precise Differential Analysis of Stellar Metallicities: Application to Solar Analogs Including 16 Cyg A and B
A method is presented for very accurately establishing the differencesof the atmospheric parameters (the effective temperature, the surfacegravity, the microturbulent velocity, and the Fe abundance) between twosimilar stars by using the equivalent widths of Fe I and Fe II lines,which is a variant of the numerical solution-search approach developedby Takeda et al. (2002, PASJ, 54, 451), while being inspired by thespirit of the orthodox ``differential curve-of-growth'' procedure. Byapplying this technique to eight selected stars similar to the Sun [HD20630, 76151, 134987, 181655, 186408 (16 Cyg A), 186427 (16 Cyg B),195019, and 217014] along with the Sun itself, the parameter differencesbetween any pairs of these stars could be successfully determined toprecisions of 10 K (in ΔTeff), 0.02dex (inΔlog g), 0.02 km s-1 (in Δv t), and 0.01 dex (in ΔA Fe). Regarding 16 Cyg A and B, awell-known ``solar twin'' system where a planet has been detected onlyin B, the metallicities of these two components were concluded to beessentially the same to a level of ≲ 0.01 dex.
| Abundance difference between components of wide binaries
We present iron abundance analysis for 23 wide binaries with mainsequence components in the temperture range 4900-6300 K, taken from thesample of the pairs currently included in the radial velocity planetsearch on going at the Telescopio Nazionale Galileo (TNG) using the highresolution spectrograph SARG. The use of a line-by-line differentialanalysis technique between the components of each pair allows us toreach errors of about 0.02 dex in the iron content difference. Most ofthe pairs have abundance differences lower than 0.02 dex and there areno pairs with differences larger than 0.07 dex. The four cases ofdifferences larger than 0.02 dex may be spurious because of the largererror bars affecting pairs with large temperature difference, cold starsand rotating stars. The pair HD 219542, previously reported by us tohave a different composition, here is shown to be normal. Fornon-rotating stars warmer than 5500 K, characterized by a thinnerconvective envelope and for which our analyis appears to be of higheraccuracy, we are able to exclude in most cases the consumption of morethan 1 Earth Mass of iron (about 5 Earth masses of meteoritic material)during the main sequence lifetime of the stars, placing more stringentlimits (about 0.4 Earth masses of iron) in five cases of warm stars.This latter limit is similar to the estimates of rocky material accretedby the Sun during its main sequence lifetime. Combining the results ofthe present analysis with those for the Hyades and Pleiades, we concludethat the hypothesis that pollution by planetary material is the onlymechanism responsible for the highest metallicity of the stars withplanets may be rejected at more than 99% level of confidence if theincidence of planets in these samples is as high as 8% and similar tothe field stars included in current radial velocity surveys. However,the significance of this result drops considerably if the incidence ofplanets around stars in binary systems and clusters is less than a halfof that around normal field stars.Based on observations made with the Italian Telescopio Nazionale Galileo(TNG) operated on the island of La Palma by the Centro Galileo Galileiof the INAF (Istituto Nazionale di Astrofisica) at the SpanishObservatorio del Roque de los Muchachos of the Instituto de Astrofisicade Canarias.The equivalent widths 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/420/683
| 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
| 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.
| Metallicity Trends Among Stars With Planets - 2002
To date about 100 giant planets have been discovered around nearbysun-like stars. About 50 of these have received detailed spectroscopicanalysis. They tend to be more metal-rich than the average nearby fieldstar. We review three possible explanations proposed to explain thispattern and whether extant data help to choose among them.
| 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.
| Non-interacting main-sequence binaries with different chemical compositions: Evidences of infall of rocky material?
We performed a careful differential abundance analysis of individualcomponents of six main sequence binaries with separations of a fewhundreds of AU. To reduce analysis concerns, we selected systems withalmost equal mass components. We were able to derive differentialabundances of several elements with errors down to 0.01 dex in the bestcases. We found that in four systems the two components have the samechemical composition, within these very severe limits. However, cleardifferences were found for the two remaining systems (HD 219542 and HD200466), in both cases the primaries being more Fe-rich than thesecondaries, by 0.091+/- 0.009 and 0.053+/- 0.024 dex respectively.Similar differences were found for most of the elements considered inour analysis; however, we found no appreciable difference for volatileelements and a trend for increasing abundance differences withincreasing condensation temperature for individual elements, a resultsimilar to that found for some single stars with planets by Smith et al.(\cite{Smith01}). Finally, we note that HD 219542A has a Li-abundancecomparable to those of Li-rich stars in old open clusters, while no Liis detected in the slightly cooler HD 219542B. We suggest that theprimaries of these two systems have accreted rocky planets or the innerdust-rich part of a protoplanetary disk, likely due to gravitationalperturbation caused by the presence of the companion. Based onobservations made with the Italian Telescopio Nazionale Galileo (TNG)operated on the island of La Palma by the Centro Galileo Galilei of theCNAA (Consorzio Nazionale per l'Astronomia e l'Astrofisica) at theSpanish Observatorio del Roque de los Muchachos of the Instituto deAstrofisica de Canarias. Table 1 is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp: //cdsweb .u-strasbg .fr/ cgi-bin/qcat?J/A+A/377/123
| SARG: the high resolution spectrograph of TNG.
Not Available
| Classification of Population II Stars in the Vilnius Photometric System. II. Results
The results of photometric classification of 848 true and suspectedPopulation II stars, some of which were found to belong to Population I,are presented. The stars were classified using a new calibrationdescribed in Paper I (Bartkevicius & Lazauskaite 1996). We combinethese results with our results from Paper I and discuss in greaterdetail the following groups of stars: UU Herculis-type stars and otherhigh-galactic-latitude supergiants, field red horizontal-branch stars,metal-deficient visual binaries, metal-deficient subgiants, stars fromthe Catalogue of Metal-deficient F--M Stars Classified Photometrically(MDPH; Bartkevicius 1993) and stars from one of the HIPPARCOS programs(Bartkevicius 1994a). It is confirmed that high galactic latitudesupergiants from the Bartaya (1979) catalog are giants or even dwarfs.Some stars, identified by Rose (1985) and Tautvaisiene (1996a) as fieldRHB stars, appear to be ordinary giants according to our classification.Some of the visual binaries studied can be considered as physical pairs.Quite a large fraction of stars from the MDPH catalog are found to havesolar metallicity. A number of new possible UU Herculis-type stars, RHBstars and metal-deficient subgiants are identified.
| CCD astrometry and instrumental {DELTA}V photometry of wide visual double stars. IV. Differential measurements of northern pairs.
We present relative positions and instrumental visual magnitudedifferences ({DELTA}V) of 101 northern wide double star components. Themean accuracy of the magnitude differences is 0.01 magnitudes, of theangular separation 0.04 arcseconds, and of position angle 0.13 degrees.Most of the programme pairs are targets of the HIPPARCOS mission andthey have been often observed during the last 150 years.
| 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.
| A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
| Search for systematic effects in photographic measurements of visual binaries
Photographic plates (265) of selected visual double stars obtained bymeans of the 105 cm astrometric reflector of the AstronomicalObservatory of Torino have been taken during 1984. 118 visual doublestars of this series of observations (the 7th) have been measured twiceby two persons using two different measuring machines. In this paper thesingle measures of the polar coordinates for each person and the averagevalues obtained combining the two types of measures are reported. Ananalysis of the systematic errors due to the two systems of measurementand considerations about the type of motion of each binary are given.
| Three-dimensional calssification of F-M type halo stars in the Vilnius photometric system
Not Available
| Photographic measures of double stars. II
Measures are presented for 302 double stars photographed on 657 plateswith the 36-in. Lick refractor in the period between 1945 and 1962. Thedata provided include the observing epochs, the rectangular coordinatesof the secondary components with reference to the respective primaries,the mean errors of a single measurement, the computed mean errors, thedouble-star separations, and the position angles both for the observingepoch and reduced to the equator of 2000. An additional 561 unmeasuredplates of acceptable quality obtained between 1948 and 1960 are listed.
| Mesures photographiques d'étoiles doubles
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..409F&db_key=AST
| Micrometer measures of doubles stars. III.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68...57V&db_key=AST
| Spectral Classifications for New or Unclassified Emission-Line Carbon and s, Long-Period Variable, and Double Stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1961ApJ...133..920N
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| קבוצת-כוכבים: | ברבור |
| התרוממות ימנית: | 21h02m21.91s |
| סירוב: | +37°39'14.0" |
| גודל גלוי: | 8.374 |
| מרחק: | 43.802 פארסק |
| תנועה נכונה: | -66.9 |
| תנועה נכונה: | -219.7 |
| B-T magnitude: | 9.252 |
| V-T magnitude: | 8.447 |
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