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The Chromospheric Activity, Age, Metallicity, and Space Motions of 36 Wide Binaries
We present the chromospheric activity (CA) levels, metallicities, andfull space motions for 41 F, G, K, and M dwarf stars in 36 wide binarysystems. Thirty-one of the binaries contain a white dwarf (WD)component. In such binaries, the total age can be estimated by addingthe cooling age of the WD to an estimate of the progenitor'smain-sequence lifetime. To better understand how CA correlates tostellar age, 14 cluster member stars were also observed. Ourobservations demonstrate for the first time that, in general, CA decayswith age from 50 Myr to at least 8 Gyr for stars with 1.0 <= V - I<= 2.4. However, little change occurs in the CA level for stars withV - I < 1.0 between 1 Gyr and 5 Gyr, consistent with the results ofPace et al. Our sample also exhibits a negative correlation between thestellar age and metallicity, a positive correlation between the stellarage and W space velocity component, and the W velocity dispersionincreases with age. Finally, the population membership of these widebinaries is examined based upon their U, V, W kinematics, metallicity,and CA. We conclude that wide binaries are similar to field and clusterstars in these respects. More importantly, they span a much morecontinuous range in age and metallicity than is afforded by nearbyclusters.
| Disk and Halo Wide Binaries from the Revised Luyten Catalog: Probes of Star Formation and MACHO Dark Matter
We present a catalog of 1147 candidate common proper motion binariesselected from the revised New Luyten Two-Tenths Catalog (NLTT). Amongthese, we identify 999 genuine physical pairs using the measuredproper-motion difference and the relative positions of each binary'scomponents on a reduced proper motion (RPM) diagram. The RPM positionsalso serve to classify them as either disk main-sequence pairs (801),halo subdwarf (116) pairs, or pairs containing at least one white dwarf(82). The disk and halo samples are complete to separations ofΔθ=500'' and Δθ=900'',which correspond to ~0.1 and ~1 pc, respectively. At wide separations,both distributions are well described by single power lawsdN/dΔθ~(Δθ)-α, withα=1.67+/-0.07 for the disk and α=1.55+/-0.10 for the halo.The fact that these distributions have similar slopes (and similarnormalizations as well) argues for similarity of the star formationconditions of these two populations. The fact that the halo binariesobey a single power law out to ~1 pc permits strong constraints on halodark matter candidates. At somewhat closer separations(10''<~Δθ<~25''), the diskdistribution shows a pronounced flattening, which is detected at veryhigh statistical significance and is not due to any obvious systematiceffect. We also present a list of 11 previously unknown halo stars withparallaxes that are recognized here as companions of Hipparcos stars.
| Completeness of USNO-B for High Proper Motion Stars
I test the completeness of USNO-B detections of high proper motion(μ>180 mas yr-1) stars and the accuracy of itsmeasurements by comparing them to the revised New Luyten Two-Tenthscatalog of Salim & Gould. For 14.5~20 mas yr-1) may actuallyhave still larger errors than tabulated.
| 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.
| Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog
We present refined coordinates and proper-motion data for the highproper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. Thepositional uncertainty in the original Luyten catalog is typicallygreater than 10" and is often greater than 30". We have used the digitalscans of the POSS I and POSS II plates to derive more accurate positionsand proper motions of the objects. Out of the 4470 candidates in the LHScatalog, 4323 objects were manually reidentified in the POSS I and POSSII scans. A small fraction of the stars were not found because of thelack of finder charts and digitized POSS II scans. The uncertainties inthe revised positions are typically ~2" but can be as high as ~8" in afew cases, which is a large improvement over the original data.Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819candidates (with mR<~12). For these brighter sources, theposition and proper-motion data were replaced with the more accurateTycho-2/Hipparcos data. In total, we have revised proper-motionmeasurements and coordinates for 4040 stars and revised coordinates for4330 stars. The electronic version of the paper5 contains the updated information on all 4470stars in the LHS catalog.
| High proper motion stars with declinations between -30o and -40o, and right ascensions between 00 h and 10 h 40 m
Proper motions, positions, finding charts and magnitudes are given for147 newly discovered stars with proper motions larger than 0.15arcsec/year. They were found in a search for high proper motion starscarried out in thirteen 5o x 5o areas, locatedbetween -30o and -40o in declination, and 00 h and10 h 40 m in right ascension. Their blue photographic magnitudes rangefrom approximately 9.0 to 18.5. Nine objects from the above sample haveproper motions larger than 0.4 (0.404 to 0.550) arcsec/year. The sametype of data is also presented for 149 Luyten Catalogue (LTT, Luyten\cite{Luyten57}) stars re-discovered during the above search. Anestimated precision level between 6 and 22 mas/year was achieved for theproper motions. Tables 2 and 3 are 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/367/725 Figures 4 and 5are only available in electronic form at http://www.edpsciences.org
| Astrometric positions of stars with high proper motions in the Southern Hemisphere
Several stars with large proper motions, cited by W.J. Luyten, wereincluded in the preliminary programme for the HIPPARCOS mission. Whenperforming preparatory measurements of plates, difficulties wereencountered in identifying certain of these stars when relying only onpublished coordinates. We have taken advantage of this work whichrelates to the southern sky in order to determine the astrometricposition of the greatest possible number of these objects, even forthose which were not included in the programme. Catalogue is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| Halo common proper motion stars - Subdwarf distance scale, halo binary fraction, and UBVRI colors
Common proper motion stars identified by Luyten (1979, 1980) wereselected according to reduced proper motion and photometric criteria toproduce a list of candidate halo objects. UBVRI photometry was obtainedto identify genuine halo parts. About 20 percent of the stars with(Fe/H) less than -1.0 were found to have random errors not less thanseveral x 0.1 mag in distance modulus, in addition to the photometricerrors, thought to be due to the existence of close binary companions tosome of the common proper motion stars. The implications of these errorsfor kinematic studies of field Population II stars are considered.Systematic errors of order 16 percent were also detected in distancesderived from the U-B,B-V deblanketing technique. It is suggested thatPopulation II field stars did not originate in globular clusters whichsubsequently disintegrated but formed in less dense environments.Several K subdwarfs were found with very high UV excesses, comparablewith those predicted by some synthetic colors.
| Subdwarf studies. II - Abundances and kinematics from medium resolution spectra. III - The halo metallicity distribution
Stars previously identified as having UV excesses are observed at 1-Aresolution in the Ca II K-line region. Comparisons of these data withother samples and with Monte Carlo simulations involving a singlecomponent halo have yielded estimates of halo velocity dispersions androtation velocity, corrected for the kinematic biases in the sample. Itis suggested that the data are not consistent with a model in which thehalo formed from star formation in a dissipating, collapsing cloud; theyare, however, reconcilable with the formation of the halo stars bynumerous, independently evolving gas clouds. The metallicitydistribution of a sample of 372 kinematically selected halo stars isthen constructed, with a view to selection effects in the data. Goodagreement is noted between the globular cluster metallicity distributionand a stochastic model with a mean of 10 enrichments/fragment.
| Identifications and limited spectroscopy for Luyten common proper motion stars with probable white dwarf components. I - Pair brighter than 17th magnitude
Identifications are provided for 103 bright Luyten common proper motion(CPM) stellar systems with m(pg) less than 17.0 mag containing likelywhite dwarf (WD) components. New spectral types are presented for 55components, and spectral types for 51 more are available in theliterature. With the CPM systems previously published by Giclas et al.(1978), the Luyten stars provide a uniform sample of nearly 200 pairs ormultiples brighter than 17h magnitude. Selection effects biasing thecombined samples are discussed; in particular, evidence is presentedthat fewer than 1 percent of wide WD binaries have been detected.
| 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.
| Optical polarization of stars of galactic latitudes b-45 degres.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...23..125S&db_key=AST
| Determinations of Color Classes for 204 Stars of Large Proper Motion.
Abstract image available at:http://adsabs.harvard.edu/abs/1952ApJ...116..587C
| Stellar parallaxes determined photographically at the Cape Observatory (Eighteenth List)
Not Available
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