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Speckle Observations of Composite Star Candidates
Speckle observations are reported for 53 stars with composite spectraselected from the Michigan Spectral Catalogue in an effort to improvethe orbits of known binaries and to discover new binaries among thisclass of objects. The data were obtained using the 1.3 and 2.4 mtelescopes at the Michigan-Dartmouth-MIT Observatory and the GeorgiaTech Research Institute speckle imaging system. For 50 stars in thesample for which no indication of duplicity was found in our data, wemay place an upper limit of <=0.2" on the separations at the epochsof observation. Three stars were resolved, including HD 26796, alsodiscovered to be double by Hipparcos. A discussion of the accuracy ofthe measurements based on comparisons with speckle standard stars ispresented.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| 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
| The vertical structure of our galaxy. I - Methods of quantitative objective prism spectroscopy
The methods employed to determine the spectral types and log g and Fe/Hvalues for Galactic F-K stars in the vertical-structure investigation ofRose and Agustinho (1991) are described in detail. IIaO objective-prismplates obtained with the Curtis Schmidt telescope at CTIO using a 10-degprism and a 135-A FWHM interference filter centered at 408 nm aredigitized, and three spectral indices defined by Rose (1984) aremeasured and used to calculate the desired parameters. Results fromtests of the accuracy of this method are presented, and it is shown thatreliable separation of G dwarfs from G giants/subgiants is possible downto B = 13.
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| Metal-abundance determinations from near-UV spectra - Application to the mean metal abundance of M32
Near-UV spectra for the nucleus of the elliptical galaxy M32 and for 60field stars have been obtained which cover the wavelength interval3200-3900 A at a resolution of 2.5 A FWHM. A depression in thepseudocontinuum shortward of 3504 A is found to be quite sensitive tometal abundance. The results indicate that the luminosity-weighted meanmetal Fe/H abundance ratio for M32 at 3500 A is about -0.1, and that thegiant branch contributes slightly less than 30 percent of the light at4000 A. The luminosity-weighted N/Fe abundance ratio is shown to beapproximately equal to that of solar neighborhood stars.
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
| Red horizontal-branch stars in the galactic disk
A quantitative, three-dimensional spectral classification systemdeveloped by Rose (1984), which uses 2.5-A resolution spectra in theblue, has been used to identify a class of red horizontal branch (RHB)stars in the Galactic disk that are similar to those in the 'metal rich'globular cluster M 71. The RHB are denoted as evolved stars by their SrII 4077 line, and are distinguished from post-main sequence starsevolving through the same region of the HR diagram on the basis of theunique appearance of their CN 3883 and 4216 A bands. The RHB starsconsitute at least 5 percent of the entire giant branch population ofthe disk.
| MK classification for F- and G-type stars. IV
MK spectral classifications are given for 112 stars brighter than mv =7.5, having HD types F2-G5. The classifications were made on slitspectrograms of dispersion 75 A/mm at H gamma.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | נחש מים |
| התרוממות ימנית: | 08h23m56.19s |
| סירוב: | -01°29'52.8" |
| גודל גלוי: | 6.92 |
| מרחק: | 183.486 פארסק |
| תנועה נכונה: | -14.8 |
| תנועה נכונה: | -19 |
| B-T magnitude: | 7.797 |
| V-T magnitude: | 6.993 |
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