Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
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
| Observations of Mira stars with the IOTA/FLUOR interferometer and comparison with Mira star models
We present K/'-band observations of five Mira stars with the IOTAinterferometer. The interferograms were obtained with the FLUOR fiberoptics beam combiner, which provides high-accuracy visibilitymeasurements in spite of time-variable atmospheric conditions. For theM-type Miras X Oph, R Aql, RU Her, R Ser, and the C-type Mira V CrB wederived the uniform-disk diameters 11.7 mas, 10.9 mas, 8.4 mas, 8.1 mas,and 7.9 mas (/+/-0.3 mas), respectively. Simultaneous photometricobservations yielded the bolometric fluxes. The derived angularRosseland radii and the bolometric fluxes allowed the determination ofeffective temperatures. For instance, the effective temperature of R Aqlwas determined to be 2970/+/-110 K. A linear Rosseland radius for R Aqlof 250+100-60Rsolar was derived fromthe angular Rosseland radius of 5.5+/-0.2mas and the HIPPARCOS parallaxof 4.73+/-1.19mas. The observations were compared with theoretical Mirastar models of Bessel et al. [A&A 307 (1996) 481] and Hofmann et al.[A&A 339 (1998) 846]. The effective temperatures of the M-type Mirasand the linear radius of R Aql indicate fundamental mode pulsation.
| Do red giant stars pulsate in high overtones?
About 30 photometrically variable red giant stars have periods less than10d, as determined by the compilers of the Hipparcos Catalogue fromHipparcos photometric measurements. These periods, when combined withestimates of the radii and masses of these stars, and with pulsationtheory, imply that these stars are pulsating in very high overtones. Wepresent several pieces of evidence which suggest that the periods may bespurious, as a result of the particular aliasing properties of theHipparcos photometry. We conclude that the evidence for high-overtonepulsation in red giant stars is equivocal.
| 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/
| 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).
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| A library of 0.5 to 2.5 mu m spectra of luminous cool stars
We present a library of 0.5-2.5 mu m digital spectra of cool, mostlyvariable, giant and supergiant stars which should be useful for spectralsynthesis applications, as well as for comparison with theoretical modelatmosphere calculations. The library includes carbon stars, GalacticBulge and Magellanic Cloud stars, and OH/IR stars. The stars observedcover a range of metallicities and masses. Most variable objects wereobserved several times, at different phases of their pulsation cycle. Wediscuss the effects of various fundamental parameters and of variabilityon the spectra. Based on period-luminosity relations and stellarevolutionary tracks, we tentatively assign initial masses to eachobject.
| Speckle Interferometry of New and Problem HIPPARCOS Binaries
The ESA Hipparcos satellite made measurements of over 12,000 doublestars and discovered 3406 new systems. In addition to these, 4706entries in the Hipparcos Catalogue correspond to double star solutionsthat did not provide the classical parameters of separation and positionangle (rho,theta) but were the so-called problem stars, flagged ``G,''``O,'' ``V,'' or ``X'' (field H59 of the main catalog). An additionalsubset of 6981 entries were treated as single objects but classified byHipparcos as ``suspected nonsingle'' (flag ``S'' in field H61), thusyielding a total of 11,687 ``problem stars.'' Of the many ground-basedtechniques for the study of double stars, probably the one with thegreatest potential for exploration of these new and problem Hipparcosbinaries is speckle interferometry. Results are presented from aninspection of 848 new and problem Hipparcos binaries, using botharchival and new speckle observations obtained with the USNO and CHARAspeckle cameras.
| 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
| Stellar radii of M giants
We determine the stellar radii of the M giant stars in the Hipparcoscatalogue that have a parallax measured to better than 20% accuracy.This is done with the help of a relation between a visual surfacebrightness parameter and the Cousins (V - I) colour index, which wecalibrate with M giants with published angular diameters.The radii of(non-Mira) M giants increase from a median value of 50 R_Sun at spectraltype M0 III to 170 R_Sun at M7/8 III. Typical intermediate giant radiiare 65 R_Sun for M1/M2, 90 R_Sun for M3, 100 R_Sun for M4, 120 R_Sun forM5 and 150 R_Sun for M6. There is a large intrinsic spread for a givenspectral type. This variance in stellar radius increases with latertypes but in relative terms, it remains constant.We determineluminosities and, from evolutionary tracks, stellar masses for oursample stars. The M giants in the solar neighbourhood have masses in therange 0.8-4 M_Sun. For a given spectral type, there is a close relationbetween stellar radius and stellar mass. We also find a linear relationbetween the mass and radius of non-variable M giants. With increasingamplitude of variability we have larger stellar radii for a given mass.
| Accurate Positions for 45 Variables in Five Fields
Accurate positions of 45 variables in 5 fields, determined fromphotographic astrometry, are presented.
| GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
Not Available
| 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.
| 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.
| On the spectra and photometry of M-giant stars
From a sample of 97 very bright M-giant stars in the Solarneighbourhood, high-quality "intrinsic" spectra in the spectral range380 <~ λ[nm] <~ 900 for all M-spectral subtypes of the Caseand MK classification systems are obtained. The results are fitted tophotospheric synthetic spectra in the range 99 <~ λ [nm]<=12500 in order to infer the corresponding continua. The syntheticspectra are also compared to the intrinsic spectra. The effectivetemperatures are derived and mathematical spectral classificationcriteria are found. The (UB)_j_(VRI)_c_(JHKLM)_ESO_ photometric data ofthe sample are also given. The data are available on the StrasbourgAstronomical Data Centre (CDS).
| Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension
Not Available
| A new library of stellar optical spectra
Attention is given to a new digital optical stellar library consistingof spectra covering 3510-8930 R at 11-A resolution for 72 differentstellar types. These types extend over the spectral classes O-M andluminosity classes I-V. Most spectra are of solar metallicity stars butsome metal-rich and metal-poor spectra are included. This new library isquantitatively compared to two previously published libraries. It offersseveral advantages over them: it is photometrically well-calibratedindividually and consistently from star to star. Good temperature andluminosity coverage has been achieved. The incorporation of stars withwell-determined temperature, metallicity, and surface gravity parametersincreases the accuracy of the spectral type assigned to each compositelibrary star.
| 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
| 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
| Models for IRAS observations of circumstellar dust shells around late-type stars
IRAS observations of circumstellar dust shells around late-type starsare compared with the models of Rowan-Robinson and Harris (1982, 1983).It is shown that the IRAS data at 12 and 25 microns agree well withprevious observations and models. The predicted fluxes at 60 microns andabove are found to depend sensitively on the overall extent of the dustshells. Models for circumstellar dust shells around carbon and M starsare compared with IRAS observations at 60 and 100 microns and are foundto agree reasonably well with model predictions. For M stars, the IRASdata at 60 and 100 microns require a grain absorption efficiency between25-30 and 100 microns.
| Transformation equations and other aids for VRI photometry
Transformations among VRI systems are commonly beset by Paschen-jumpeffects, for which fully satisfactory allowance has not previously beenmade. This paper describes two new techniques which are based on thework of Gutierrez-Moreno, and which allow fully for the effects of thePaschen jump. Values of E(V-R)/E(B-V) and E(R-I)/E(B-V) are also givenfor the Cousins system for a wide range of temperatures. These and thenew techniques contribute to a set of new transformation relations whichapply for most VRI systems; the status of the remaining systems isreviewed, and future work needed for them is described. Two majorsources of Cousins VRI data underlie the new relations; the consistencyof these sources is reviewed and found to be generally satisfactory,although more work on this question is needed. Finally, three tables oftransformed standard-star and other data are given for the Cousins andJohnson systems, and a description of ways to reproduce the latter ispresented.
| 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.
| 1985 revised MK spectral standards : stars GO and later
Not Available
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Szűz |
| Rektaszcenzió: | 12h38m22.40s |
| Deklináció: | +01°51'17.0" |
| Vizuális fényesség: | 5.71 |
| Távolság: | 153.61 parszek |
| RA sajátmozgás: | -80.5 |
| Dec sajátmozgás: | -17.8 |
| B-T magnitude: | 7.725 |
| V-T magnitude: | 5.883 |
Katalógusok és elnevezések:
|
INHABITED SKY
