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Empirically Constrained Color-Temperature Relations. II. uvby
A new grid of theoretical color indices for the Strömgren uvbyphotometric system has been derived from MARCS model atmospheres and SSGsynthetic spectra for cool dwarf and giant stars having-3.0<=[Fe/H]<=+0.5 and 3000<=Teff<=8000 K. Atwarmer temperatures (i.e., 8000-2.0. To overcome thisproblem, the theoretical indices at intermediate and high metallicitieshave been corrected using a set of color calibrations based on fieldstars having well-determined distances from Hipparcos, accurateTeff estimates from the infrared flux method, andspectroscopic [Fe/H] values. In contrast with Paper I, star clustersplayed only a minor role in this analysis in that they provided asupplementary constraint on the color corrections for cool dwarf starswith Teff<=5500 K. They were mainly used to test thecolor-Teff relations and, encouragingly, isochrones thatemploy the transformations derived in this study are able to reproducethe observed CMDs (involving u-v, v-b, and b-y colors) for a number ofopen and globular clusters (including M67, the Hyades, and 47 Tuc)rather well. Moreover, our interpretations of such data are verysimilar, if not identical, with those given in Paper I from aconsideration of BV(RI)C observations for the sameclusters-which provides a compelling argument in support of thecolor-Teff relations that are reported in both studies. Inthe present investigation, we have also analyzed the observedStrömgren photometry for the classic Population II subdwarfs,compared our ``final'' (b-y)-Teff relationship with thosederived empirically in a number of recent studies and examined in somedetail the dependence of the m1 index on [Fe/H].Based, in part, on observations made with the Nordic Optical Telescope,operated jointly on the island of La Palma by Denmark, Finland, Iceland,Norway, and Sweden, in the Spanish Observatorio del Roque de losMuchachos of the Instituto de Astrofisica de Canarias.Based, in part, on observations obtained with the Danish 1.54 mtelescope at the European Southern Observatory, La Silla, Chile.
| A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars
Rotational velocity vsin i and mean radial velocity are presented for asample of 231 Ib supergiant stars covering the spectral region F, G andK. This work is the second part of the large survey carried out with theCORAVEL spectrometer to establish the behavior of the rotation for starsevolving off the main sequence (De Medeiros & Mayor 1999). Thesedata will add constraints to the study of the rotational behavior inevolved stars, as well as solid information concerning tidalinteractions in binary systems and on the link between rotation,chemical abundance and activity in stars of intermediate masses. Basedon observations collected at the Haute-Provence Observatory,Saint-Michel, France and at the European Southern Observatory, La Silla,Chile Table 1 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/395/97
| Sodium enrichment of stellar atmospheres. I. Non-variable supergiants and bright giants
48 supergiants and bright giants have been observed in order toinvestigate the sodium enrichment of their atmospheres and itsconnection with stellar gravity. We present the equivalent widths of the6154 Å and 6160 Å Na I lines measured from the programspectra, the results of effective temperature determinations, the NLTEsodium abundances, and the derived relation between the sodiumoverabundance and surface gravity.
| 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 effective temperature scale of giant stars (F0-K5). II. Empirical calibration of Teff versus colours and [Fe/H]
We present calibrations of the effective temperatures of giant starsversus [Fe/H] and colours (U-V), (B-V), (R-I), (V-R), (V-I), (V-K),(J-H), (J-K), (I-K), (V-L'), (b-y) and (u-b). These calibrations arebased on a large sample of field and globular cluster stars whichroughly cover spectral types from F0 to K5. Their effectivetemperatures, scaled to direct Teff determinations viareliable angular diameter measurements, were derived by applying theinfrared flux method. The empirical relations have been fitted topolynomials of the form theta_ {eff} = P(colour,[Fe/H]) by using theleast squares method. The precision of the fits ranges from 40 K for(V-K) to 170 K for (J-H). We tabulate intrinsic colours of giant starsin the ranges: 3500 K <= Teff <= 8000 K; -3.0 <=[Fe/H] <= +0.5. We also present the calibration of BC(V) as afunction of log(Teff) and metallicity. Finally, we comparethe resulting scale of temperatures with previous works.
| The effective temperature scale of giant stars (F0-K5). I. The effective temperature determination by means of the IRFM
We have applied the InfraRed Flux Method (IRFM) to a sample ofapproximately 500 giant stars in order to derive their effectivetemperatures with an internal mean accuracy of about 1.5% and a maximumuncertainty in the zero point of the order of 0.9%. For the applicationof the IRFM, we have used a homogeneous grid of theoretical modelatmosphere flux distributions developed by \cite[Kurucz (1993)]{K93}.The atmospheric parameters of the stars roughly cover the ranges: 3500 K<= T_eff <= 8000 K; -3.0 <= [Fe/H] <= +0.5; 0.5 <= log(g) <= 3.5. The monochromatic infrared fluxes at the continuum arebased on recent photometry with errors that satisfy the accuracyrequirements of the work. We have derived the bolometric correction ofgiant stars by using a new calibration which takes the effect ofmetallicity into account. Direct spectroscopic determinations ofmetallicity have been adopted where available, although estimates basedon photometric calibrations have been considered for some stars lackingspectroscopic ones. The adopted infrared absolute flux calibration,based on direct optical measurements of stellar angular diameters, putsthe effective temperatures determined in this work in the same scale asthose obtained by direct methods. We have derived up to fourtemperatures, TJ, TH, TK and T_{L'},for each star using the monochromatic fluxes at different infraredwavelengths in the photometric bands J, H, K and L'. They show goodconsistency over 4000 K, and there is no appreciable trend withwavelength, metallicity and/or temperature. We provide a detaileddescription of the steps followed for the application of the IRFM, aswell as the sources of error and their effect on final temperatures. Wealso provide a comparison of the results with previous work.
| Broad-band JHK(L') photometry of a sample of giants with 0.5 > [Fe/H] > -3
We present the results of a three-year campaign of broad-band photometryin the near-infrared J, H, K and L' bands for a sample of approximately250 giant stars carried out at the Observatorio del Teide (Tenerife,Spain). Transformations of the Telescopio Carlos Sanchez systeminto/from several currently used infrared systems are extended to theredward part of the colour axis. The linearity of our photometric systemin the range -3 mag [Fe/H] >-3. Data of comparable quality previouslypublished have been added to the sample in order to increase thereliability of the relations to be obtained. We also provide mean IRcolours for giant stars according to spectral type.ables 1, 2 and 3 are only available in electronic form via the CDS(anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html
| Temperatures for A0-K0 Supergiants from 13-Color Photometry
Observations on the 13-color photometric system are reported for 71A0-K0 supergiant stars brighter than V=6.0. Three independent methods todetermine the effective temperatures for A0-K0 supergiants from their13C photometry are discussed: 1) Calibrations between T$eff$and reddening-free indices are developed; temperatures were collectedfrom the literature for the calibration stars, and most of them werespectroscopically determined. 2) An empirical correlation betweenintrinsic colors in the 13C system and T$eff$ has beenderived. 3) The unreddened colors are compared with synthetic colorscalculated by Kurucz (1989); this leads to simultaneous estimates forT$eff$ and log $g$. The estimated uncertainties inT$eff$ by the three methods are comparable and areapproximately plus or minus 200-300K. (SECTION: Stars)
| Barium stars, galactic populations and evolution.
In this paper HIPPARCOS astrometric and kinematical data together withradial velocities from other sources are used to calibrate bothluminosity and kinematics parameters of Ba stars and to classify them.We confirm the results of our previous paper (where we used data fromthe HIPPARCOS Input Catalogue), and show that Ba stars are aninhomogeneous group. Five distinct classes have been found i.e. somehalo stars and four groups belonging to disk population: roughlysuper-giants, two groups of giants (one on the giant branch, the otherat the clump location) and dwarfs, with a few subgiants mixed with them.The confirmed or suspected duplicity, the variability and the range ofknown orbital periods found in each group give coherent resultssupporting the scenario for Ba stars that are not too highly massivebinary stars in any evolutionary stages but that all were previouslyenriched with Ba from a more evolved companion. The presence in thesample of a certain number of ``false'' Ba stars is confirmed. Theestimates of age and mass are compatible with models for stars with astrong Ba anomaly. The mild Ba stars with an estimated mass higher than3Msun_ may be either stars Ba enriched by themselves or``true'' Ba stars, which imposes new constraints on models.
| Absolute magnitudes and kinematics of barium stars.
The absolute magnitude of barium stars has been obtained fromkinematical data using a new algorithm based on the maximum-likelihoodprinciple. The method allows to separate a sample into groupscharacterized by different mean absolute magnitudes, kinematics andz-scale heights. It also takes into account, simultaneously, thecensorship in the sample and the errors on the observables. The methodhas been applied to a sample of 318 barium stars. Four groups have beendetected. Three of them show a kinematical behaviour corresponding todisk population stars. The fourth group contains stars with halokinematics. The luminosities of the disk population groups spread alarge range. The intrinsically brightest one (M_v_=-1.5mag,σ_M_=0.5mag) seems to be an inhomogeneous group containing bariumbinaries as well as AGB single stars. The most numerous group (about 150stars) has a mean absolute magnitude corresponding to stars in the redgiant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group containsbarium dwarfs, the obtained mean absolute magnitude is characteristic ofstars on the main sequence or on the subgiant branch (M_v_=3.3mag,σ_M_=0.5mag). The obtained mean luminosities as well as thekinematical results are compatible with an evolutionary link betweenbarium dwarfs and classical barium giants. The highly luminous group isnot linked with these last two groups. More high-resolutionspectroscopic data will be necessary in order to better discriminatebetween barium and non-barium stars.
| Classification of Population II Stars in the Vilnius Photometric System. I. Methods
The methods used for classification of Population II stars in theVilnius photometric system are described. An extensive set of standardswith known astrophysical parameters compiled from the literature sourcesis given. These standard stars are classified in the Vilnius photometricsystem using the methods described. The accuracy of classification isevaluated by a comparison of the astrophysical parameters derived fromthe Vilnius photometric system with those estimated from spectroscopicstudies as well as from photometric data in other systems. For dwarfsand subdwarfs, we find a satisfactory agreement between our reddeningsand those estimated in the uvbyscriptstyle beta system. The standarddeviation of [Fe/H] deter mined in the Vilnius system is about 0.2 dex.The absolute magnitude for dwarfs and subdwarfs is estimated with anaccuracy of scriptstyle <=0.5 mag.
| Colour excesses of F-G supergiants and Cepheids from Geneva photometry.
A reddening scale for F-G supergiants and Cepheids is presented.Supergiants with low reddenings or in clusters form the basis of thecalibration. In this sense, it is entirely empirical. The data have beenobtained in the Geneva photometric system. Comparisons with otherreddening scales show no disagreement. The only problem is with Fernie'sscale for Cepheids (1990), where a systematic trend exists. Its originis not clear. It is suggested to extend the number of supergiants withindependently obtained colour excesses in order to test the existence ofa possible luminosity dependence of the calibration. A period-colourrelation for Cepheids is deduced, on the basis of the present reddeningcorrections. It gives strong support for V473 Lyr being a secondovertone pulsator.
| 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.
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| Classification of Population II supergiants and related stars in the Vilnius system
The results of photometric classification in the Vilnius system of 117Population II supergiants, suspected supergiants, and related stars aregiven. Their photometric spectral types, intrinsic color indices (Y-V)0,color excesses E(Y-V), metallicities Fe/H, and absolute magnitudes MVare determined. It is shown that the system allows us to detect the UUHerculis-type supergiants photometrically. The analyzed SRd star samplefalls into two groups of metallicity and luminosity. Our photometricclassification assigns luminosity classes from III to V to 37 F-K starswith /b/ greater than 16 deg classified by Bartaya (1979) from objectiveprism spectra as supergiants.
| Radial-velocity measurements. V - Ground support of the HIPPARCOS satellite observation program
The paper presents data on 1070 radial velocity measurements of starsdistributed in 39 fields measuring 4 deg x 4 deg. The PPO series ofFehrenbach et al. (1987) and Duflot et al. (1990) is continued using theFehrenbach objective prism method.
| CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
| Taxonomy of barium stars
Spectral classification, barium intensity, radial velocity, luminosity,and kinematical properties are determined for 389 barium stars byanalyzing image-tube spectra and photometric observation data. Diskkinematics for the stars are based on whether they are Ba weak or Bastrong. Weak barium stars in general have smaller velocity dispersions,brighter apparent magnitude, and lower luminosity than strong bariumstars. These characteristics are confirmed by solving for meanspectroscopic distances, z-scale height distances, and reduced propermotions.
| 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.
| An uvby-beta catalogue of F0-K0 supergiant stars brighter than V = 6.5
Photoelectric uvby-beta photometry is reported for 111 F0-K0 supergiantstars which are brighter than V = 6.5 mag and located betweendeclination of -15 and +61 deg. A comparison with previous observationsis made. A few stars which are suspected to present light variations arementioned.
| Photoelectric Photometry of 241 Stars in the Vilnius System
Not Available
| Groups of stars with common motion in the Galaxy - Groups of red supergiants of the luminosity classes I and II
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.
| Spectrophotometry of several yellow supergiants
Spectrophotometric observations of 20 F, G, and K spectral classsupergiants and bright giants have been obtained with the HarvardCollege Observatory scanner on the No. 10.9 m telescope at Kitt PeakNational Observatory. The scans cover the wavelength range 3510-5520 Awith a resolution of 30 A. The observed flux distributions have beencorrected for instrumental effects, atmospheric extinction, andinterstellar reddening. The resulting intrinsic flux distributions havebeen compared to theoretical flux distributions based on the model ofKurucz (1979) in order to estimate effective temperatures and surfacegravities for eight of these stars.
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| A search for lithium-rich giant stars
Lithium abundances or upper limits have been determined for 644 brightG-K giant stars selected from the DDO photometric catalog. Two of thesegiants possess surface lithium abundances approaching the 'cosmic' valueof the interstellar medium and young main-sequence stars, and eight moregiants have Li contents far in excess of standard predictions. At leastsome of these Li-rich giants are shown to be evolved to the stage ofhaving convectively mixed envelopes, either from the direct evidence oflow surface carbon isotope ratios, or from the indirect evidence oftheir H-R diagram positions. Suggestions are given for the uniqueconditions that might have allowed these stars to produce or accrete newlithium for their surface layers, or simply to preserve from destructiontheir initial lithium contents. The lithium abundance of the remainingstars demonstrates that giants only very rarely meet the expectations ofstandard first dredge-up theories; the average extra Li destructionrequired is about 1.5 dex. The evolutionary states of these giants andtheir average masses are discussed briefly, and the Li distribution ofthe giants is compared to predictions of Galactic chemical evolution.
| 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.
| Observational evidence for mass loss from classical Cepheids
This paper examines the evidence for mass loss from classical Cepheidvariables in the light of recent observational studies of infrared andultraviolet emission from these objects. Mass-loss rates derived forseveral stars range between 10 to the -10th solar masses/yr and 10 tothe -6th solar masses/yr. The lower end of this range probablycorresponds to the majority of classical Cepheids. Nonvariablesupergiants show, on average, a somewhat lower rate of infrared excess,but have mass-loss rates of the same order of magnitude as the Cepheids.On the basis of the observations to date, mass loss alone isinsufficient in explaining the Cepheid mass discrepancy, indicating thatadjustments to the evolutionary or pulsation models present a betterprospect of resolving this discrepancy.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hattyú |
| Rektaszcenzió: | 21h14m10.30s |
| Deklináció: | +29°54'04.0" |
| Vizuális fényesség: | 6.17 |
| Távolság: | 746.269 parszek |
| RA sajátmozgás: | 5.2 |
| Dec sajátmozgás: | -1.6 |
| B-T magnitude: | 7.581 |
| V-T magnitude: | 6.289 |
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