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Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is 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/430/165}
| Evidence of a Black Hole in the X-Ray Transient GS 1354-64 (=BW Circini)
We present the first radial velocity curve of the companion star to BWCir that demonstrates the presence of a black hole in this X-raytransient that recorded outbursts in 1987 and 1997 (and possibly1971-1972). We identify weak absorption features corresponding to a G0-5III donor star, strongly veiled by a residual accretion disk thatcontributes 61%-65% of the total light at 6300 Å. The Dopplermotions of these features trace an orbit of P=2.54448 days (or its 1 yralias of P=2.56358 days) and a velocity semiamplitudeK2=279+/-5 km s-1 (or K2=292+/-5 kms-1). Both solutions are equally possible. The mass functionimplied by the shorter period solution is f(M)=5.75+/-0.30Msolar, which, when combined with the rotational broadeningof the tidally locked companion (Vsini=71+/-4 km s-1), yieldsa compact object mass of M1sin3i=7.34+/-0.46 Msolar.This is substantially above the mass of a neutron star under anystandard equation of state of nuclear matter. The companion star isprobably a G subgiant that has evolved off the main sequence in order tofill its Roche lobe. Remarkably, a distance of >=27 kpc is inferredby the companion's luminosity, and this is supported by the largeobserved systemic velocity (γ=103+/-4 km s-1), whichrequires such a distance in order to be consistent with the Galacticrotation curve.
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The photometric variability of the Be star NW Serpentis
{NW Ser} is a bright (V = 6.1 - 6.2) active Be star which is known tovary photometrically on a time scale of hours to days. Using bothHipparcos and ground-based photometry, and using light curve,autocorrelation, power spectrum analysis and phase dispersionminimalization techniques, we have concluded that the period is close to0.46d - a period typical of stars of this type, and in good agreementwith the value of 0.488d, recently determined by Hubert & Floquetfrom Hipparcos data. It is possible that the period is near twice thisvalue, but the evidence is not strong. We also find a period of about5d. from both the ground-based and Hipparcos data.
| 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.
| Reliable photometric reductions to the standard UBV (or uvby) system and accurate UBV magnitudes of bright standard stars from the northern part of the international Be program
A modified method of computer reduction of UBV (or uvby) photoelectricobservations to standard systems, which combines advantages of what hasso far been achieved in this area, is described in detail. A completereduction of over 46000 UBV observations obtained at Hvar Observatorybetween 1972 and 1991, and of nearly 5000 UBV observations secured atSkalnate Pleso Observatory between 1980 and 1987, was carried out usingthe new technique. It is argued that replacing the original Johnson'sUBV values for the non-variable stars that were observed by the meanvalues based on repeated observations over several years and applyingthe new reduction technique can ensure a stable reproduction of UBVmagnitudes, obviously quite close to the standard Johnson's ones, overmany years and from observatories situated at very different altitudesabove sea level within about 0.01mag in all three UBV magnitudes. A listof new accurate mean UBV values of 191 stars which were regularlyobserved at Hvar - and a part of them also at Skalnate Pleso - ascomparison, check and standard stars in the Be- and Ap-star observingprograms, is included for future use by photometric observers in theNorthern Hemisphere. For a number of these stars, we can guaranteesecular constancy within 0.mag01 during the past 5 to 15 years.
| Photoelectric photometry of G-M stars in the Vilnius system
Not Available
| Photoelectric monitoring of bright Be stars
The paper describes and summarizes BV photometric observations of 34bright, active Be stars made at various times between 1981 and 1987 witha 0.4-m telescope at the University of Toronto. These observationsdemonstrate the photometric variability of Be stars on time scales ofhours to years.
| ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars
A survey of a sample of 672 stars from the Yale Bright Star Catalog(Hoffleit, 1982) has been carried out using speckle interferometry onthe 3.6-cm Canada-France-Hawaii Telescope in order to establish thebinary star frequency within the sample. This effort was motivated bythe need for a more observationally determined basis for predicting thefrequency of failure of the Hubble Space Telescope (HST) fine-guidancesensors to achieve guide-star lock due to duplicity. This survey of 426dwarfs and 246 evolved stars yielded measurements of 52 newly discoveredbinaries and 60 previously known binary systems. It is shown that thefrequency of close visual binaries in the separation range 0.04-0.25arcsec is 11 percent, or nearly 3.5 times that previously known.
| Speckle observations of the ice feature in the young double source Serpens SVS 20
One-dimensional near-infrared speckle observations of the ice feature ofthe low-luminosity infrared double source Serpens SVS 220 are reported.The depth of the 3.1-micron feature is found to be the same for bothcomponents of SVS 20, suggesting that the ice-carrying grains belong tothe material distributed on a larger scale within the Serpens molecularcloud. The results indicate that the two components of SVS 20 may suffersimilar optical extinctions and have a similar intrinsic energydistribution. It is suggested that both stars of SVS 20 have not yetreached the T Tauri stage and may still be embedded in circumstellardust shells.
| Catalogue of stars with CaII H and K emissions
Not Available
| Absolute magnitudes of stars from widths of chromospheric CaII emission lines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...205..823W&db_key=AST
| UBV photometry of 550 F, G and K type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.133..475A&db_key=AST
| Magnitudes and colors for 833 Northern and Southern stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955AJ.....60...65E&db_key=AST
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| קבוצת-כוכבים: | נושא הנחש |
| התרוממות ימנית: | 18h27m50.30s |
| סירוב: | +03°44'55.0" |
| גודל גלוי: | 6.07 |
| מרחק: | 420.168 פארסק |
| תנועה נכונה: | -1.9 |
| תנועה נכונה: | -7.4 |
| B-T magnitude: | 8.168 |
| V-T magnitude: | 6.231 |
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