Contents
Images
Upload your image
DSS Images Other Images
Related articles
Elemental abundances in the atmosphere of clump giants
Aims.The aim of this paper is to provide the fundamental parameters andabundances for a large sample of local clump giants with a highaccuracy. This study is a part of a big project, in which the verticaldistribution of the stars in the Galactic disc and the chemical anddynamical evolution of the Galaxy are being investigated. Methods:.The selection of clump stars for the sample group was made applying acolour-absolute magnitude window to nearby Hipparcos stars. Theeffective temperatures were estimated by the line depth ratio method.The surface gravities (log {g}) were determined by two methods (thefirst one was the method based on the ionization balance of iron and thesecond one was the method based on fitting of the wings of the Ca I6162.17 Å line). The abundances of carbon and nitrogen wereobtained from the molecular synthetic spectrum, and the Mg and Naabundances were derived using the non-LTE approximation. The "classical"models of stellar evolution without atomic diffusion androtation-induced mixing were employed. Results: .The atmosphericparameters ({T_eff}, log {g}, [Fe/H], {Vt}) and Li, C, N, O,Na, Mg, Si, Ca, and Ni abundances in 177 clump giants of the Galacticdisc were determined. The underabundance of carbon, overabundance ofnitrogen, and "normal" abundance of oxygen were detected. A small sodiumoverabundance was found. A possibility of a selection of the clumpgiants based on their chemical composition and the evolutionary trackswas explored. Conclusions: .The theoretical predictions based onthe classical stellar evolution models are in good agreement with theobserved surface variations of the carbon and nitrogen just after thefirst dredge-up episode. The giants show the same behaviour of thedependencies of O, Mg, Ca, and Si (α-elements) and Ni (iron-peakelement) abundances vs. [Fe/H] as dwarfs do. This allows us to use suchabundance ratios to study the chemical and dynamical evolution of theGalaxy.
| 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}
| The Rotation of Binary Systems with Evolved Components
In the present study we analyze the behavior of the rotational velocity,vsini, for a large sample of 134 spectroscopic binary systems with agiant star component of luminosity class III, along the spectral regionfrom middle F to middle K. The distribution of vsini as a function ofcolor index B-V seems to follow the same behavior as their singlecounterparts, with a sudden decline around G0 III. Blueward of thisspectral type, namely, for binary systems with a giant F-type component,one sees a trend for a large spread in the rotational velocities, from afew to at least 40 km s-1. Along the G and K spectral regionsthere are a considerable number of binary systems with moderate tomoderately high rotation rates. This reflects the effects ofsynchronization between rotation and orbital motions. These rotatorshave orbital periods shorter than about 250 days and circular or nearlycircular orbits. Except for these synchronized systems, the largemajority of binary systems with a giant component of spectral type laterthan G0 III are composed of slow rotators.
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/297
| Spectral and luminosity classification for the cool components in symbiotic stars
The near infrared spectra of 12 S-type symbiotic stars and 78 comparisonstars have been observed with moderate dispersion in five runs from 1992to 1997, the resolving power being R= (lambda )/(Delta lambda )>2000,with a signal to noise ratio S/N>100. The triple-headed absorptionband of TiO (lambda lambda 8432, 8422 and 8452 Ä) emerges when astar is later than M2, and the depth of the TiO absorption band is verysensitive to the spectral type (ST) and insensitive to the luminosityclass of the star. We fit a curve of spectral type against the index ofthe absorption depth of this band with a standard deviation sigma =0.37of a subdivision of one spectral type. The IR CaII triplet (lambdalambda 8498, 8542, 8662 Ä ), Fe I 8689 Ä, and Fe I 8675 Äare good luminosity indicators although the equivalent widths (EWs) ofthese lines clearly decrease for a star later than M3. When the star isa supergiant, the lines have a smaller central residual intensity andbroader wings than in the case of a normal giant. The Ca II 8662 Ä/Fe I 8675 Ä and Fe I 8689 Ä /Fe I 8675 Ä ratios are alsogood luminosity indicators for K-type giants. The latter is particularlyuseful when there are abundance anomalies. The metal-poor symbiotic starAG Dra is classified as a Ib or II giant, as is TX CVn, on the basis ofFe I 8689 Ä /Fe I 8675 Ä. 9 other symbiotic stars containingM-type cool components are classified as giants by direct comparison andquantitative analysis. Due to there being no known good ratio indicatorof luminosity for M-type stars in the band studied and because there isno metal abundance data for the symbiotic stars studied by us except forAG Dra, the results for these 9 symbiotic stars are only preliminary.The infrared Ca II triplet of most symbiotic stars clearly variesbetween the different observing runs. The different luminosity classesgiven to the same symbiotic star are probably caused by the variabilityof the lines of ionized elements, while in some cases they are affectedby a low metal abundance.
| 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
| 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.
| On the link between rotation and coronal activity in evolved stars.
We analyse the behaviour of coronal activity as a function of rotationfor a large sample of single and binary evolved stars for which we haveobtained CORAVEL high precision rotational velocities. This study showsthat tidal effects play a direct role in determining the X-ray activitylevel in binary evolved stars. The circularisation of the orbit is anecessary property for enhanced coronal activity in evolved binarystars.
| The correction in right ascension of 508 stars determinated with PMO photoelectric transit instrument.
Not Available
| Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars
Results are presented of an extensive X-ray survey of 380 giant andsupergiant stars of spectral types from F to M, carried out with theEinstein Observatory. It was found that the observed F giants orsubgiants (slightly evolved stars with a mass M less than about 2 solarmasses) are X-ray emitters at the same level of main-sequence stars ofsimilar spectral type. The G giants show a range of emissions more than3 orders of magnitude wide; some single G giants exist with X-rayluminosities comparable to RS CVn systems, while some nearby large Ggiants have upper limits on the X-ray emission below typical solarvalues. The K giants have an observed X-ray emission level significantlylower than F and F giants. None of the 29 M giants were detected, exceptfor one spectroscopic binary.
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| Narrow-band photometry of late-type stars. II
This paper presents extensive narrow-band photometry in the Uppsalasystem supplementing earlier published mesurements so that data now areavailable for all late-type stars brighter than V = 6.05 and a number ofgalactic cluster members. Numerous UBV and BV measurements are alsopublished. The data are used to determine relations for the predictionof UBV intrinsic colors for late-type stars from the narrow-bandmeasurements. The main purpose of the data is to constitute the basisfor the determination of solar-neighborhood space densities of late-typestars, mainly giants of different kinds; these space densities will becombined with narrow-band data for fainter stars in the north Galacticpole region to yield the decrease of space density with distance fromthe galactic plane for many kinds of late-type stars.
| Positions moyennes et mouvements propres de 355 etoiles DU GC de la zone de declinaison +33 +36.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...26..219M&db_key=AST
| MK classifications for F-and G-type stars. 3.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..682H&db_key=AST
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
| Radial Velocities of 360 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...115..157W&db_key=AST
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | さんかく座 |
| Right ascension: | 02h32m52.50s |
| Declination: | +34°32'33.0" |
| Apparent magnitude: | 5.83 |
| Distance: | 79.745 parsecs |
| Proper motion RA: | -51.6 |
| Proper motion Dec: | -16.9 |
| B-T magnitude: | 7.224 |
| V-T magnitude: | 5.948 |
Catalogs and designations:
|
INHABITED SKY
