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New Hipparcos-based Parallaxes for 424 Faint Stars
We present a catalog of 424 common proper-motion companions to Hipparcosstars with good (>3 σ) parallaxes, thereby effectively providingnew parallaxes for these companions. Compared with typical stars in theHipparcos catalog, these stars are substantially dimmer. The catalogincludes 20 white dwarfs and an additional 29 stars withMV>14, the great majority of the latter being M dwarfs.
| 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.
| 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.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| CCD astrometry and instrumental Delta-V photometry of wide visual double stars. III - Differential measurements of often observed southern pairs
We present accurate relative positions and instrumental visual (BesselV) magnitude differences of southern wide star components. The meanaccuracy of the angular separation is 0.02 arcsecs, which corresponds to1.5 micron on the CCD chip, and of magnitude difference 0.007mag/exposure. The program pairs are targets of the HIPPARCOS mission andthey have been observed at least four times in the last 150 yrs.
| A photometric study of wide visual double stars. IV - UVBY photometry of wide visual double stars with G-type primaries
We performed uvby aperture photometry of wide visual double stars withG-type primaries. The minimum angular separation of the components is 10arcsecs and mainly less than 20 arcsecs. As both components have oftensimilar photometric and astrophysical parameters, we infer that most ofthese double stars have components of common origin.
| Visual measurements of southern double stars
A double-star observing program is described which has been started atCordoba with a 30 cm refractor. Usually neglected Index Catalog ofVisual Double Stars (IDS) pairs south of -60 deg are selected forobservation, most of them having been measured only one or two timespreviously. A total of 174 micrometric observations of 78 wide pairs arepresented together with a few measurements of 9 double stars not foundin the IDS. Also reported is a list of 135 additional measurements of 26test stars. By comparison with all earlier observations, an estimate forthe personal equation has been made, which is applied in combinationwith catalogue proper motions to investigate the nature of many of thesepairs.
| Erratum - Discordances Between SAO and HD Numbers for Bright Stars
Not Available
| Fundamental data for southern stars (First list)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957MNRAS.117..534E&db_key=AST
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Observation and Astrometry data
| Constellation: | Οκτάς |
| Right ascension: | 20h41m43.70s |
| Declination: | -75°21'02.0" |
| Apparent magnitude: | 6.55 |
| Distance: | 43.573 parsecs |
| Proper motion RA: | 155.7 |
| Proper motion Dec: | -161.7 |
| B-T magnitude: | 7.193 |
| V-T magnitude: | 6.51 |
Catalogs and designations:
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INHABITED SKY
