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A Multi-Wavelength Study of the H II Region Sharpless 217
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| 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).
| B stars and the chemical evolution of the Galactic disk
We determine stellar parameters and He, C, N, O, Mg, Al, and Siabundances of a sample of 16 early B main-sequence stars ingalactocentric distances of RGC=5-14 kpc by reanalyzing andextending the observations of Kaufer et al. (1994) towards the Galacticcenter. The analysis uses Kurucz atlas 9 lte atmospheres andGiddings-Butler detail/surface non-lte line formation. It is shown thatbeside non-lte effects the metallicity of the underlying atmosphere hasa non-negligible impact on the temperature structure and the subsequentline formation. The local field is found to have an underabundance ofabout -0.2\:{dex} relative to the Sun. Contrary to part of recent B-starand H ii-region determinations we derive an oxygen abundance gradientDelta [O/H]/Delta RGC=(-0.07+/- 0.02)\:{dex/kpc} for theGalactic disk, typical for normal spiral galaxies of similar Hubbletype. This steep gradient is in contrast to the recent evidence that (a)our Milky Way is actually a barred spiral galaxy, and (b) barredgalaxies generally have almost flat abundance gradients throughout theirdisks. Comparing our results with numerical models of the chemodynamicalevolution of barred galaxies we derive an age of about 1 Gyr for thecentral bar structure of the Galaxy. We argue that our bar is still tooyoung to exert a notable flattening effect on the chemical abundancegradient of the Galactic disk. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile, and at theGerman-Spanish Astronomical Center, Calar Alto, Spain.
| 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.
| UBV photometry of stars whose positions are accurately known. VI
Results are presented from UBV photometric observations of 1000 stars ofthe Bright Star Catalogue and the faint extension of the FK5.Observations were carried out between July 1987 and December 1990 withthe 40-cm Cassegrain telescope of the Kvistaberg Observatory.
| 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.
| The rotation and structure of the galaxy beyond the solar circle. I - Photometry and spectroscopy of 276 stars in 45 H II regions and other young stellar groups toward the galactic anticentre
Abstract image available at:http://adsabs.harvard.edu/abs/1979A&AS...38..197M
| Spectral and Luminosity Classifications and Measurements of the Strength of Cyanogen Absorption for Late-Type Stars from Objective-Prism Spectra.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...134..809Y&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hiúz |
| Rektaszcenzió: | 07h29m52.32s |
| Deklináció: | +56°58'19.2" |
| Vizuális fényesség: | 8.543 |
| Távolság: | 680.272 parszek |
| RA sajátmozgás: | -0.7 |
| Dec sajátmozgás: | -15.1 |
| B-T magnitude: | 9.773 |
| V-T magnitude: | 8.645 |
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