Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
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}
| High resolution spectroscopy over lambda lambda 8500-8750 Å for GAIA. IV. Extending the cool MK stars sample
A library of high resolution spectra of MK standard and reference stars,observed in support to the GAIA mission, is presented. The aim of thispaper is to integrate the MK mapping of Paper I of this series as wellas to consider stars over a wider range of metallicities. Radialvelocities are measured for all the target stars.The spectra are available in electronic form (ASCII format) at CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/406/995 and from the webpage http://ulisse.pd.astro.it/MoreMK/, where further bibliographicalinformation for the target stars is given.
| 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
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| A multi-epoch spectrophotometric atlas of symbiotic stars
A multi-epoch, absolute-fluxed spectral atlas extending from about 3200to 9000 Å is presented for 130 symbiotic stars, including membersof the LMC, SMC and Draco dwarf galaxies. The fluxes are accurate tobetter than 5% as shown by comparison with Tycho and ground-basedphotometric data. The spectra of 40 reference objects (MKK cool giantstandards, Mira and Carbon stars, planetary nebulae, white dwarfs, hotsub-dwarfs, Wolf-Rayet stars, classical novae, VV Cep and Herbig Ae/Beobjects) are provided to assist the interpretation of symbiotic starspectra. Astrometric positions and counterparts in astrometriccatalogues are derived for all program symbiotic stars. The spectra areavailable in electronic form from the authors. Based on observationscollected with the telescopes of the European Southern Observatory (ESO,Chile) and of the Padova & Asiago Astronomical Observatories(Italy). Tables 2 and 3 are only available in electronic form (a) at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/188, and (b) from thepersonal home page http://ulisse.pd.astro.it/symbio_atlas/ Figures 4-256are only available in electronic form (a) at http://www.edpsciences.organd (b) from the personal home pagehttp://ulisse.pd.astro.it/symbio_atlas/
| Envelope tomography of long-period variable stars III. Line-doubling frequency among Mira stars
This paper presents statistics of the line-doubling phenomenon in asample of 81 long-period variable (LPV) stars of various periods,spectral types and brightness ranges. The set of observations consistsof 315 high-resolution optical spectra collected with the spectrographELODIE at the Haute-Provence Observatory, during 27 observing nights atone-month intervals and spanning two years. When correlated with a maskmimicking a K0III spectrum, 54% of the sample stars clearly showed adouble-peaked cross-correlation profile around maximum light, reflectingdouble absorption lines. Several pieces of evidence are presented thatpoint towards the double absorption lines as being caused by thepropagation of a shock wave through the photosphere. The observation ofthe Balmer lines appearing in emission around maximum light in thesestars corroborates the presence of a shock wave. The observed velocitydiscontinuities, ranging between 10 and 25 km s-1, are notcorrelated with the brightness ranges. A comparison with thecenter-of-mass (COM) velocity obtained from submm CO lines originatingin the circumstellar envelope reveals that the median velocity betweenthe red and blue peaks is blueshifted with respect to the COM velocity,as expected if the shock moves upwards. The LPVs clearly exhibitingline-doubling around maximum light with the K0III mask appear to be themost compact ones, the stellar radius being estimated from theireffective temperatures (via the spectral type) and luminosities (via theperiod-luminosity relationship). It is not entirely clear whether or notthis segregation between compact and extended LPVs is an artefact of theuse of the K0III mask. Warmer masks (F0V and G2V) applied to the mostextended and coolest LPVs yield asymmetric cross-correlation functionswhich suggest that line doubling is occurring in those stars as well.Although a firm conclusion on this point is hampered by the largecorrelation noise present in the CCFs of cool LPVs obtained with warmmasks, the occurrence of line doubling in those stars is confirmed bythe double CO Delta v = 3 lines observed around 1.6 mu m by Hinkle etal. (1984, ApJS, 56, 1). Moreover, the Hdelta line in emission, which isanother signature of the presence of shocks, is observed as well in themost extended stars, although with a somewhat narrower profile. This isan indication that the shock is weaker in extended than in compact LPVs,which may also contribute to the difficulty of detecting line doublingin cool, extended LPVs. Based on observations made at Observatoire deHaute Provence, operated by the Centre National de la RechercheScientifique, France. Table 3 is only available in electronic form athttp://www.edpsciences.org and 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/379/305
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable 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/qcar?J/A+A/367/521
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Revision and Calibration of MK Luminosity Classes for Cool Giants by HIPPARCOS Parallaxes
The Hipparcos parallaxes of cool giants are utilized in two ways in thispaper. First, a plot of reduced parallaxes of stars brighter than 6.5,as a function of spectral type, for the first time separates members ofthe clump from stars in the main giant ridge. A slight modification ofthe MK luminosity standards has been made so that luminosity class IIIbdefines members of the clump, and nearly all of the class III stars fallwithin the main giant ridge. Second, a new calibration of MK luminosityclasses III and IIIb in terms of visual absolute magnitudes has beenmade.
| Accurate Positions for 45 Variables in Five Fields
Accurate positions of 45 variables in 5 fields, determined fromphotographic astrometry, are presented.
| 1--4 MU M Spectroscopy of Very Red Stars Found in an I-Band Objective Prism Survey
We present the 1.2--4.2 mu m spectroscopy of stars found in an objectiveprism survey of the galactic plane by Stephenson (1992, AAA 55.002.010).These stars were thought by Stephenson to be heavily reddened byinterstellar absorption. However, almost all of them have turned out tobe late-type stars with clear 2.3 mu m CO absorption, which means thatthey are intrinsically red as well. A few stars have AV ~ 9, but mostof them are only moderately reddened (AV = 1--5).
| 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.
| An Atlas of the infrared spectral region. II. The late-type stars (G - M)
This Atlas illustrates the behavior of late type stars (F, G, K and M)in the near infrared 8400-8800 Angstrom region with a resolution ofabout 2 degrees. Seventeen figures illustrate the spectral sequence andluminosity classes V, III, Ib and Ia. Four figures illustrate peculiarspectra, namely those of Am stars, composites, weak metal stars and Sand C type objects. The complete Atlas is also available as FITS filesfrom the CDS de Strasbourg and other data centers.
| Photometric survey near the main Galactic meridian: 2.1. Finding charts and photoelectric U,B,V,R stellar magnitudes in 26 fields. Photometric properties of the night sky at Mount Terskol observatory
Finding charts and photoelectric magnitudes of stars in the \ubvr\system in 26 fields of the MEGA programme are presented. This part ofthe photometric survey near the Main Galactic Meridian includes thefields with right ascentions 8(h) < alpha < 16(h) 30(m) anddeclinations -2(deg) < delta < 58(deg) . Together with the findingcharts of 2.5(deg) x2.5(deg) the equatorial coordinates of the stars aregiven for epoch and equinox 1950. Photometric properties of the nightsky at the Mount Terskol observatory near Mount Elbrus are derived fromthe photoelectric observations.
| Photometric Survey Near the Main Galactic Meridian - Part One - Photoelectric Stellar Magnitudes and Colours in the UBVR System
Not Available
| 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.
| Photometric surveys of suspected small-amplitude red variables. 3: an AAVSO photometric photometry survey
We have carried out a survey of the photometric (V) variability of 61'known' or suspected small-amplitude red variables, mostly M giants.Approximately two-thirds appear to be variable; several suspectedvariable comparison stars have also been identified. The incidence andaverage amplitude of variability increase rapidly from spectral type M0III to M6 III.
| Spectral classifications in the near infrared of stars with composite spectra. I. The study of MK standards.
Up to now the spectral classifications of the cool components ofcomposite spectra obtained in the 3800-4800A wavelength region have beenvery disparate. These disparities are due to the fact that the spectraof the evolved cool component are strongly veiled by that of the hotterdwarf component, which makes a classification very difficult. We proposeto study these systems in the near infrared (8380-8780A). In thisspectral domain the magnitude difference between the spectra of thecomponents is in general sufficiently large so that one observespractically only the spectrum of the cool component. In this first paperwe provide, for a sample of MK standards, the relations between theequivalent width (Wlambda_ ) of certain lines and thespectral classifications. For the cool G, K and M type stars, the linesconsidered are those of the calcium triplet (Ca II 8498, 8542 and 8662),of iron (Fe I 8621 and 8688), of titanium (Ti I 8426 and 8435) and ofthe blend λ8468. The use of certain line intensity ratiospermits, after eliminating partially the luminosity effects, a firstapproach to the spectral type. For the hotter stars of types O, B, A andF we study the behavior of the hydrogen lines (P12 and P14), the calciumlines (Ca II 8498 and 8542) as well as those of the oxygen (O I 8446).The latter line presents a very characteristic profile for stars of lowrotation and therefore in Am stars, which are frequently found among thecomposite spectrum binaries. Among the cooler stars of our sample, only6% present real anomalies with respect to the MK classifications. Thisresult is very encouraging for undertaking the classification of asample of composite spectra. The spectra were taken at the Observatoirede Haute-Provence (OHP) with the CARELEC spectrograph at the 193 cmtelescope, with a dispersion of 33 A/mm.
| Asymptotic giant branch stars near the sun
Available red and near-infrared photometry and apparent motions of M, S,and C asymptotic giant branch (AGB) stars in the Bright Star Catalogueare tabulated and discussed. It is shown that the red and near infraredindices normally used for late-type stars are interchangeable except forcarbon stars. The M-type giants are variable with visual amplitudegreater than 0.05 mag. The reddening-free parameter m2 from Genevaphotometry is essentially a temperature parameter for M giants, whilethe reddening-free parameter d is a sensitive detector of blue stellarcompanions. The space density of AGB stars near the sun decreases by afactor of 35 in a temperature range 3800 to 3400 K. Two of the S starsnear the sun were found to have nearly equal space motions and may becomembers of the Arcturus group.
| Third list of corrections to the identifications of IRAS sources in Astron. & Astrophys Suppl. 65, 607 and Astron. J. 98, 931
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.
| A list of MK standard stars
Not Available
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| Lunar occultations of IRAS point sources, 1991-2000
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989ApJS...69..651C&db_key=AST
| 1988 Revised MK Spectral Standards for Stars GO and Later
Not Available
| A spectroscopic survey of high-latitude fields and comparison to Galaxy models
The results of a spectroscopic survey of the stellar populations ofhigh-Galactic latitude fields in SA 94 and Serpens are presented andanalyzed. A set of six spectrophotometric indices is used to provideinformation on both the number and metallicity of evolved stars, whilemeasurement of another 11 spectrophotometric indices provides anestimate of (Fe/H) good to 0.25 dex for the evolved stars identified ineach field. A detailed comparison of the data with predictions of thestandard Bahcall-Soneira Galaxy model reveals serious discrepancies. Theproperties of giants with roughly solar metallicity are described wellby the disk giants predicted by the standard model. The sample isdominated by intermediate-metallicity giants whose properties are welldescribed by a thick-disk component with scale height of approximately700 pc that makes up about 5 percent of the solar neighborhood stellardensity.
| The cool components of symbiotic stars. I - Optical spectral types
An analysis of prominent absorption features on red spectra of symbioticstars is presented. The depths of TiO and VO bands appear to becorrelated with the brightness of the system; this behavior is probablythe result of the secondary star heating the outer atmosphere of thecool giant. New spectral types and luminosity classes for the coolcomponents of symbiotics are derived, and these classifications suggesta division into semidetached systems and detached systems. Mass-lossrates for detached symbiotics, which do not contain Mira variables,remain higher than those estimated for single red giants of the samespectral type, suggesting that the presence of a binary companionenhances mass loss in these objects.
| Lunar occultations of IRAS point sources, 1986-1990
A complete listing is given for objects in the IRAS Point Source Catalogwhich will be occulted by the moon over the course of 1986-1990. A totalof 14,148 ASCII card images is encompassed by the complete listing ofobjects having geocentric events during this period. The resultscontained in this complete listing are illustrated in two of the presenttables for the brightest objects at 12 and 100 micron wavelengths.
| IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
| The MK classification and its calibration
The system of spectral classification is described as it has developedfrom the original Yerkes Atlas (Morgan, Keenan, Kelman 1943) untiltoday. The word 'developed' is used because any system that is to remainuseful must be flexible enough to adapt not only to improved techniquesof measurement but also to new theoretical insights into the variablesthat actually determine the energy spectrum of a star in all itsfascinating but sometimes frustrating detail. The discussion does notconsider the criteria of classification but is confined to the resultingset of temperature types and luminosity classes. Chemical composition isexamined as a third variable. Tabulated and plotted informationincludes: MK temperature subclasses; lists of MK types of fainter stars;published calibrations of luminosity classes for early-type stars;calibration of MK luminosity classes for types later than F8; thedistribution among groups of the 426 stars in the author's current listof best types; and the effects of metal deficiencies on spectra of KOIII stars. The revised MK classification can be applied to all but a fewpercent of the stars later in type than GO. For the two-thirds of thesethat have approximately solar composition no abundance index is needed;for most of the remainder one abundance index suffices.
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Рак |
| Ректацензија: | 08h59m10.80s |
| Deклинација: | +18°08'05.0" |
| Apparent магнитуда: | 6.38 |
| Даљина: | 213.675 parsecs |
| Proper motion RA: | -48.8 |
| Proper motion Dec: | -67.5 |
| B-T magnitude: | 8.321 |
| V-T magnitude: | 6.518 |
Каталог и designations:
|
INHABITED SKY
