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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Dynamical Evidence for a Black Hole in the Microquasar XTE J1550-564
Optical spectroscopic observations of the companion star (type G8 IV toK4 III) in the microquasar system XTE J1550-564 reveal a radial velocitycurve with a best-fitting spectroscopic period ofPsp=1.552+/-0.010 days and a semiamplitude ofK2=349+/-12 km s-1. The optical mass function isf(M)=6.86+/-0.71Msolar (1 σ). We tentatively measurethe rotational velocity of the companion star to beVrotsini=90+/-10 km s-1, which when taken at facevalue implies a mass ratio ofQ≡M1/M2=6.6+2.5-1.6 (1σ), using the above value of K2. We derive constraintson the binary parameters from simultaneous modeling of the ellipsoidallight and radial velocity curves. We find 1 σ ranges for thephotometric period (1.5430days<=Pph<=1.5440days),K-velocity (350.2<=K2<=368.6 km s-1),inclination (67.0d<=i<=77.4d), mass ratio (Q>=12.0), andorbital separation(11.55Rsolar<=a<=12.50Rsolar). Given thesegeometrical constraints, we find that the most likely value of the massof the compact object is 9.41 Msolar with a 1 σ rangeof 8.36Msolar<=M1<=10.76Msolar.If we apply our tentative value of Vrotsini=90+/-10 kms-1 as an additional constraint in the ellipsoidal modeling,we find 1 σ ranges of 1.5432days<=Pph<=1.5441daysfor the photometric period, 352.2<=K2<=370.1 kms-1 for the K-velocity, 70.8d<=i<=75.4d for theinclination, 6.7<=Q<=11.0 for the mass ratio, and12.35Rsolar<=a<=13.22Rsolar for the orbitalseparation. These geometrical constraints imply the most likely value ofthe mass of the compact object of 10.56 Msolar with a 1σ range of9.68Msolar<=M1<=11.58Msolar. Ineither case the mass of the compact object is well above the maximummass of a stable neutron star, and we therefore conclude that XTEJ1550-564 contains a black hole. Based on observations collected at theEuropean Southern Observatory, Chile (program 67.D-0229), at theMagellan Walter Baade Telescope at the Las Campanas Observatory, Chile,and the William Herschel Telescope operated on the island of La Palma bythe Isaac Newton Group in the Spanish Observatorio del Roque de losMuchachos of the Instituto de Astrofisica de Canarias.
| A statistical analysis of the metallicities of nine old superclusters and moving groups
Using both high-dispersion and low-resolution data, the metallicities ofnine old moving groups and superclusters are analyzed. These stellargroupings include the HR 1614 and Hyades superclusters and the Wolf 630,zeta Her, 61 Cyg, HR 1614, sigma Pup, eta Cep, and Arcturus groups.Samples of these stellar groupings are drawn from Eggen's membershiplists. Precautions are taken against problems posed by reddening, visualand spectroscopic binaries, and typographical errors in Eggen's lists.When required, the analyses allow for systematic differences betweenlow-resolution and high-dispersion metallicities. It is found that noneof the stellar groupings have the small metallicity dispersion found fora selection of galactic clusters. Instead, the metallicity dispersionsturn out to be comparable to the dispersion for a random selection offield stars. For most of the stellar groupings, it does not seempossible at present to learn more by analyzing metallicities. However,one can be more definite about three of them: the HR 1614 supercluster,the HR 1614 group, and the Hyades supercluster. Using a membership listfrom Eggen (\cite{e98c}) that is based on Hipparcos astrometry, noevidence is found for the existence of an HR 1614 supercluster. Toisolate an HR 1614 group, results from a kinematic analysis (Dehnen\cite{d98}) are then used to select a tentative list of members fromEggen's group and supercluster lists. From the mean metallicity of theredefined group, it is found that the group is very unlikely to be arandom, magnitude-limited sample of stars. A similar result is obtainedfor a version of the Hyades supercluster derived from 18 of Eggen'smembership lists. About 43% of the stars in this version turn out to bemembers of the supercluster.
| Evolutionary Oddities in Old Disk Population Clusters
With a luminosity zero point fixed by the kinematics of old disksuperclusters (HR 1614, t = 6 Gyr, [Fe/H] = +0.1 dex) and groups(Arcturus, t = 14 Gyr, [Fe/H] = -0.65 dex), the luminosities and colorsof evolved old disk stars, especially red horizontal branch (RHB), earlyasymptotic branch [AGB(1)], thermally pulsing asymptotic giant branch[AGB(2)], and sdOB stars in old disk clusters (NGC 6791, 47 Tuc, M71,M67, Mel 66, NGC 2420, NGC 2204, and NGC 2443) are discussed. (1) TheRHB stars in the old disk all have M_V = +0.7 +/- 0.1 (M_K = -1.3 +/-0.1) mag. (2) Large-amplitude red variables (LARVs) with quasi-stableperiods and light curves are old disk stars on AGB(2). (3) AGB(1)objects include CH stars and semiregular (SRa) variables. (4) Thepopulous and overabundant cluster NGC 6791 may be the only disk clusterwith sdOB stars, populating the lower portion of the bifurcated extendedhorizontal branch that is usual in most ``blue tailed'' and high-densityhalo clusters. (5) Post-red giant branch (RGB) stars in old diskclusters show a B - V (b - y) defect when compared with RGB stars,possibly because of a change in the character of the atmospheres. (6) Ifthe bulk of the LARVs are pulsating in the fundamental mode, R Vir (P =145 days) is possibly a first-overtone pulsator. (7) The overabundantold disk clusters are within the solar circle, with Liller 1 being atthe Galactic center. (8) Several probable RHB stars at the southGalactic pole are identified. (9) The period-age relation, combined withthe known spatial distribution of Galactic LARVs, leads to a relationbetween age and scale height of distribution that monotonicallyincreases with age, leaving no obvious reason for a bifurcation of thepopulation.
| The Abundance of CN. Calcium and Heavy Elements in High Velocity Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..825E&db_key=AST
| Star Streams and Galactic Structure
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.1595E&db_key=AST
| 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.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| Large and kinematically unbiased samples of G- and K-type stars. VI - Evolved stars in the Moore-Paddock-Wayman sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990PASP..102..507E&db_key=AST
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Sagittario |
| Ascensione retta: | 19h21m44.19s |
| Declinazione: | -26°09'59.0" |
| Magnitudine apparente: | 7.29 |
| Distanza: | 200.803 parsec |
| Moto proprio RA: | -11 |
| Moto proprio Dec: | -38.6 |
| B-T magnitude: | 9.184 |
| V-T magnitude: | 7.447 |
Cataloghi e designazioni:
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