Contenidos
Imágenes
Subir su imagen
DSS Images Other Images
Artículos relacionados
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}
| Technetium and the third dredge up in AGB stars. I. Field stars
We searched for Tc in a sample of long period variables selected bystellar luminosity derived from Hipparcos parallaxes. Tc, as an unstables-process element, is a good indicator for the evolutionary status ofstars on the asymptotic giant branch (AGB). In this paper we study theoccurrence of Tc as a function of luminosity to provide constraints onthe minimum luminosity for the third dredge up as estimated from recentstellar evolution models.A large number of AGB stars above the estimated theoretical limit forthe third dredge up are found not to show Tc. We confirm previousfindings that only a small fraction of the semiregular variables show Tclines in their spectra. Contrary to earlier results by Little et al.(\cite{llmb87}) we find also a significant number of Miras without Tc.The presence and absence of Tc is discussed in relation to the massdistribution of AGB stars. We find that a large fraction of the stars ofour sample must have current masses of less than 1.5 Msun .Combining our findings with stellar evolution scenarios we conclude thatthe fraction of time a star is observed as a SRV or a Mira is dependenton its mass.Partly based on observations collected at the European SouthernObservatory, Paranal, Chile (ESO-Programme 65.L-0317(A)).
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table 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/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
The absolute K magnitudes and kinematic parameters of about 350oxygen-rich Long-Period Variable stars are calibrated, by means of anup-to-date maximum-likelihood method, using Hipparcos parallaxes andproper motions together with radial velocities and, as additional data,periods and V-K colour indices. Four groups, differing by theirkinematics and mean magnitudes, are found. For each of them, we alsoobtain the distributions of magnitude, period and de-reddened colour ofthe base population, as well as de-biased period-luminosity-colourrelations and their two-dimensional projections. The SRa semiregulars donot seem to constitute a separate class of LPVs. The SRb appear tobelong to two populations of different ages. In a PL diagram, theyconstitute two evolutionary sequences towards the Mira stage. The Mirasof the disk appear to pulsate on a lower-order mode. The slopes of theirde-biased PL and PC relations are found to be very different from theones of the Oxygen Miras of the LMC. This suggests that a significantnumber of so-called Miras of the LMC are misclassified. This alsosuggests that the Miras of the LMC do not constitute a homogeneousgroup, but include a significant proportion of metal-deficient stars,suggesting a relatively smooth star formation history. As a consequence,one may not trivially transpose the LMC period-luminosity relation fromone galaxy to the other Based on data from the Hipparcos astrometrysatellite. Appendix B 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/Abstract.html
| 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.
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| 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.
| Semiregular variables of types SRa and SRb - Basic properties in the visual and the IRAS-range
The pulsational properties, T(eff)s, mass loss rates, luminosities,scale heights, and volume densities in the Galactic plane are presentedfor samples of optical semiregular variables of types SRa and SRbcorrelated with the IRAS point source catalog. These properties arecompared to the corresponding characteristics of optical Mira variables.It is found that the SRa's are not a distinct class of variables but amixture of 'intrinsic' Miras and SRb's. The O-rich SRb's form a quitehomogeneous group in terms of periods, amplitudes, and temperatures.They consist of a 'blue' group with no indication of circumstellarshells, with P less than 150 d and T(eff) greater than 3200 K, and a'red' group with temperatures and mass loss rates comparable to Mirasbut periods about a factor of two smaller. The C-rich SRVs generallyhave smaller periods and are more abundant than C-rich Miras. Theevolutionary status of the SRVs is discussed.
| First giant branch and asymptotic giant branch stars in nearby aggregates
The properties of the brightest red stars in several aggregates in theGalaxy are compared with theoretical models. 22 asymptotic giant branch(AGB) stars are identified, four of which are in the thermally pulsingAGB (TPAGB) phase and four of which are TPAGB carbon stars. Also, fourcases of RGB stars are identified which have accreted substantial massfrom the carbon-rich TPAGB precursor of a current white dwarf companion.There is general agreement between the observed and theoretical slopesof the RGB and early AGB branches, and quantitative differences betweenthe positioning of observed sequences can be understood in terms ofdifferences in metallicity and mass predicted by the theory.
| The stellar component of the galaxy as seen by the AFGL infrared sky survey
The noise-limited magnitudes for the Air Force Geophysical Laboratory(AFGL) Infrared Sky Survey have been estimated by direct comparison withground-based observations. Using these limiting magnitudes, 'pruned'versions of the AFGL catalog have been generated. Infrared observationsof all the stellar objects seen at 11, 20, or 27 microns and astatistical sample of the stars seen only at 4 microns are reported.Analysis of the observations leads to estimates of the absolute 4 and 10microns magnitudes and space densities for the two clases of objects.The expected results from the Infrared Astronomical Satellite arereexamined.
| Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
| 60th Name-List of Variable Stars
Not Available
| The classification of intrinsic variables. IV. Very-small-amplitude, very-short-period red variables
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...184..793E&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, Spectral Types, and Luminosity Classes of 820 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...112...48M&db_key=AST
|
Enviar un nuevo artículo
Enlaces relacionados
- - No se han encontrado enlaces -
En viar un nuevo enlace
Miembro de los siguientes grupos:
|
Datos observacionales y astrométricos
| Constelación: | Leo |
| Ascensión Recta: | 09h23m29.54s |
| Declinación: | +07°42'49.5" |
| Magnitud Aparente: | 6.884 |
| Distancia: | 369.004 parsecs |
| Movimiento Propio en Ascensión Recta: | -3.9 |
| Movimiento Propio en Declinación: | -42.2 |
| B-T magnitude: | 8.951 |
| V-T magnitude: | 7.055 |
Catálogos y designaciones:
|
