Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| 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
| Kinematics of Metal-poor Stars in the Galaxy. II. Proper Motions for a Large Nonkinematically Selected Sample
We present a revised catalog of 2106 Galactic stars, selected withoutkinematic bias and with available radial velocities, distance estimates,and metal abundances in the range -4.0<=[Fe/H]<=0.0. This updateof the 1995 Beers & Sommer-Larsen catalog includes newly derivedhomogeneous photometric distance estimates, revised radial velocitiesfor a number of stars with recently obtained high-resolution spectra,and refined metallicities for stars originally identified in the HKobjective-prism survey (which account for nearly half of the catalog)based on a recent recalibration. A subset of 1258 stars in this cataloghave available proper motions based on measurements obtained with theHipparcos astrometry satellite or taken from the updated AstrographicCatalogue (second epoch positions from either the Hubble Space TelescopeGuide Star Catalog or the Tycho Catalogue), the Yale/San Juan SouthernProper Motion Catalog 2.0, and the Lick Northern Proper Motion Catalog.Our present catalog includes 388 RR Lyrae variables (182 of which arenewly added), 38 variables of other types, and 1680 nonvariables, withdistances in the range 0.1 to 40 kpc.
| High resolution near-infrared polarimetry of eta Carinae and the Homunculus Nebula
High resolution near-infrared adaptive optics imaging and polarimetryhave been obtained of the Homunculus Nebula and its central illuminatingstar eta Carinae (HD 93308). Images and maps of the linear polarizationat a resolution of <0.2'' have been made in the J, H and K bands andin a narrow 2.15 mu m continuum band (K_c). The overall appearance ofthe nebula in the near-IR is similar in all bands and to that at V, withspecific features less sharp to longer wavelengths. A comparison betweenthe published HST WFPC2 1.042 mu m map and the AO J band imagedemonstrates that ground-based AO resolution can approach that of HST.The large-scale pattern of polarization vectors is centro-symmetricdemonstrating that single scattering dominates everywhere except perhapsin the central bright core. The only difference between the near-IR andoptical appearance is a narrow linear feature at position angle320o extending across the NW lobe of the Homunculus.Polarization maps at K_c in the near vicinity of eta Carinae wererestored using a PSF derived from blind deconvolution. There is adefinitely detected extension in the direction of the optically visiblespeckle knots and an estimate of 18% for the polarization of one of theknots was made. This level of polarization suggests that the knots arisein dust+gas clouds in the near environment of eta Carinae, perhaps in anequatorial disc. The most remarkable result of the linear polarizationmapping is the level of similarity in the spatial structure, and also inthe degree of linear polarization, between the near-IR and optical data.Comparison of the polarization along the projected major axis of theHomunculus shows values in the SE lobe to within a few percent from Vband to 2.2 mu m. In the NW lobe the near-IR linear polarization valuesagree to within a few percent over the 1.2-2.2 mu m range, but are upto10% lower than at V. Such a polarization pattern cannot arise in Miescattering from a single power law distribution of grain sizes unlessthe particles are very small compared with the wavelength, indisagreement with mid-IR observations. In addition the colour dependenceof the extinction was found to be shallower than the typical ISM,indicating the presence of large grains. Several possibilities areexplored to try to explain these contradictory results. Optical deptheffects and a broad distribution in grain sizes are favoured, perhapswith a dependence of the grain size with depth into the small obscuringclouds in the lobes of the Homunculus. However the presence of alignedgrains, previously inferred from mid-IR polarization, may also affectthe scattered radiation from the dust.
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 148: HR 7955
Not Available
| A Consistency Test of Spectroscopic Gravities for Late-Type Stars
Chemical analyses of late-type stars are usually carried out followingthe classical recipe: LTE line formation and homogeneous,plane-parallel, flux-constant, and LTE model atmospheres. We reviewdifferent results in the literature that have suggested significantinconsistencies in the spectroscopic analyses, pointing out thedifficulties in deriving independent estimates of the stellarfundamental parameters and hence, detecting systematic errors. Thetrigonometric parallaxes measured by the Hipparcos mission provideaccurate appraisals of the stellar surface gravity for nearby stars,which are used here to check the gravities obtained from thephotospheric iron ionization balance. We find an approximate agreementfor stars in the metallicity range -1.0<=[Fe/H]<=0, but thecomparison shows that the differences between the spectroscopic andtrigonometric gravities decrease toward lower metallicities for moremetal-deficient dwarfs (-2.5<=[Fe/H]<=-1.0), which casts a shadowupon the abundance analyses for extreme metal-poor stars that make useof the ionization equilibrium to constrain the gravity. The comparisonwith the strong-line gravities derived by Edvardsson and Fuhrmannconfirms that this method provide systematically larger gravities thanthe ionization balance. The strong-line gravities get closer to thephysical ones for the stars analyzed by Fuhrmann, but they are evenfurther away than the iron ionization gravities for the stars of lowergravities in Edvardsson's sample. The confrontation of the deviations ofthe iron ionization gravities in metal-poor stars, reported here withdepartures from the excitation balance found in the literature, showthat they are likely to be induced by the same physical mechanism.
| Acquisition and analysis of adaptive optics imaging polarimetry data
The process of data taking, reduction and calibration of near-infraredimaging polarimetry data taken with the ESO Adaptive Optics SystemADONIS is described. The ADONIS polarimetric facility is provided by arotating wire grid polarizer. Images were taken at increments of22.5(deg) of polarizer rotation from 0 to 180(deg) , over-sampling thepolarization curve but allowing the effects of photometric variations tobe assessed. Several strategies to remove the detector signature aredescribed. The instrumental polarization was determined, by observationsof stars of negligible polarization, to be 1.7% at J, H and K bands. Thelack of availability of unpolarized standard stars in the IR, inparticular which are not too bright as to saturate current IR detectors,is highlighted. The process of making polarization maps is described.Experiments at restoring polarimetry data, in order to reach diffractionlimited polarization, are outlined, with particular reference to data onthe Homunculus reflection nebula around eta Carinae.
| The ROSAT all-sky survey catalogue of the nearby stars
We present X-ray data for all entries of the Third Catalogue of NearbyStars \cite[(Gliese & Jahreiss 1991)]{gli91} that have been detectedas X-ray sources in the ROSAT all-sky survey. The catalogue contains1252 entries yielding an average detection rate of 32.9 percent. Inaddition to count rates, source detection parameters, hardness ratios,and X-ray fluxes we also list X-ray luminosities derived from Hipparcosparallaxes. Catalogue also available at CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photometric behaviour of eta Carinae, a celestial Chinese lantern: 1974-1998
We discuss 24 y of optical photometry of eta Carinae, among which newGeneva photometry made between 1994 and 1998. Various conclusions fromour previous photometric studies are confirmed. The core hides a normalS Dor variable (or LBV): it shows light variations on a time scale of1-4 y, with superimposed micro oscillations whose quasi-period indicatesa temperature in the order of 22 000 K. Therefore, a more complicatedmodel for eta Car is necessary to explain its extraordinary appearanceand phenomena exhibited in the past and at present. An analysis of thebrightness of eta Car in the ultraviolet (UV) passbands of threephotometric systems (Walraven, Strömgren and Geneva) reveals thepresence of an important variable UV source, which appears to bemodulated with the 5.52 y period of the spectroscopic events, related tothe possible revolution of an excentric binary of the type proposed byDamineli et al. (1997). Our new data support the luminous disk modelsuggested by van Genderen et al. (1994, 1995). A very hot companion ofthe LBV would be responsible for the excitation of the disk. We suspectthat the flare-like event in the X-ray flux and in the optical andnear-infrared light around 1998.0 was the result of the encounter of theinterface of the colliding winds of the binary with an arm-shapeddensity enhancement in a disk around the LBV (not necessarily ``the"luminous disk). We suppose that this encounter created an intenseX-ray/hot spot region. The subsequent steep decline of the flare isascribed to an eclipse of the X-ray/hot spot by the wind interface. Theradio flux variation of the gas torus in the equatorial plane at adistance of 2arcsec from the core, could be the result of the luminousdisk becoming optically thin. This would, obviously, start abruptly nearthe time of periastron passage and would last for a few yearsthereafter, so that a hot star, normally enshrouded by the disk, is ableto excite the outer gas torus. The creation of the X-ray/hot spot, witha life-time of at most a few months, could also be the cause of theinstantanious physical change of the luminous disk mentioned above (andits 5.52 y modulation) visible in the UV, since both happen at the sametime. Apart from the 5.52 y period in the UV, we found a striking 200d-oscillation, also in the UV, during the last orbital cycle beween1992.5 and 1998.0. Its possible explanation depends on whether it iscyclic or truly periodic (in the latter case eta Car could hide a triplestar). Based on observations obtained at the former Leiden SouthernStation in South Africa and the European Southern Observatory at LaSilla, Chile
| IRAS Detections of Metal-poor Red Giants
A number of relatively bright metal-poor red giants from the HD and BDcatalogs are found to have been detected by the IRAS satellite. Data forthese stars have been retrieved from the IRAS Point Source Catalog (PSC)and/or the Faint Source Catalog (FSC). The majority of metal-poor giantsin these samples fall along relatively well-defined sequences in plotsof V-[12] versus B-V and V-I; for these stars, the 12 μm fluxdetected is presumed to arise from the photosphere. Only a subset ofstars detected at 12 μm were detected at 25 μm these are displayedin a plot of [12]-[25] versus V-[12]. There are a small number of giantsthat exhibit notable 12 and/or 25 μm excesses relative to the meansequences defined by the bulk of the sample. Those stars with the mostunambiguous evidence for infrared excesses are variable stars, eitherlong-period or semiregular variables or RV Tauri stars. As such, thosestars exhibiting infrared excesses in the metal-poor giant sample arelikely in the asymptotic giant branch (AGB) or post-AGB phase ofevolution. There is no clear evidence for nonvariable first-ascent redgiants having been detected among the infrared-excess stars. In fact,some metal-poor red giants known to exhibit outflows in theirchromospheres do not show infrared excesses. A Population II starascending the red giant branch for the first time appears to have toolow a mass-loss rate to be recognizable as an infrared-excess star inthe IRAS PSC or FSC.
| The central depth of the Ca II triplet lines as a discriminant of chromospheric activity in late type stars
Not Available
| Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method
Effective temperatures for 420 stars with spectral types between A0 andK3, and luminosity classes between II and V, selected for a fluxcalibration of the Infrared Space Observatory, ISO, have been determinedusing the Infrared Flux Method (IRFM). The determinations are based onnarrow and wide band photometric data obtained for this purpose, andtake into account previously published narrow-band measures oftemperature. Regression coefficients are given for relations between thedetermined temperatures and the photometric parameters (B2-V1), (b-y)and (B-V), corrected for interstellar extinction through use ofHipparcos parallaxes. A correction for the effect of metallicity on thedetermination of integrated flux is proposed. The importance of aknowledge of metallicity in the representation of derived temperaturesfor Class V, IV and III stars by empirical functions is discussed andformulae given. An estimate is given for the probable error of eachtemperature determination. Based on data from the ESA HipparcosAstrometry Satellite.
| The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants
We present X-ray data for all late-type (A, F, G, K, M) giants andsupergiants (luminosity classes I to III-IV) listed in the Bright StarCatalogue that have been detected in the ROSAT all-sky survey.Altogether, our catalogue contains 450 entries of X-ray emitting evolvedlate-type stars, which corresponds to an average detection rate of about11.7 percent. The selection of the sample stars, the data analysis, thecriteria for an accepted match between star and X-ray source, and thedetermination of X-ray fluxes are described. Catalogue only available atCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The pulsating yellow supergiant V810 Centauri
The F8 Ia supergiant V810 Centauri is part of along-term high-precision photometric monitoring program on long periodvariables started twenty years ago. Time series analysis of this uniqueset of 500 data points, spanning almost fifteen years in the homogeneousGeneva photometric system, is presented. Cluster membership, physicalparameters and evolutionary status of the star are reinvestigated.Radial velocity data do not support the cluster membership toStock 14. Ultraviolet and optical spectrophotometryis combined with optical and infrared photometry to evaluate thephysical parameters of the yellow supergiant (T_eff = 5970 K, M_bol =-8.5, R = 420 Rsun) and of its B0 III companion. Fromtheoretical stellar evolutionary tracks, an initial mass of ~ 25Msun is estimated for V810 Cen, which isactually at the end of its first redward evolution. V810Cen is a multi-periodic small amplitude variable star, whoseamplitudes are variable with time. The period of the main mode, ~ 156 d,is in agreement with the Period-Luminosity-Colour relation forsupergiants. This mode is most probably the fundamental radial one.According to the theoretical pulsation periods for the radial modes,calculated from a linear non-adiabatic analysis, the period of theobserved second mode, ~ 107 d, is much too long to correspond to thefirst radial overtone . Thus, this second mode could be a non-radialp-mode. Other transient periods are observed, in particular at ~ 187 d.The length of this period suggests a non-radial g-mode. Then, thecomplex variability of V810 Cen could be due to amixing of unstable radial and non-radial p- and g-modes. Based onobservations collected at the Swiss 40~cm and 70~cm and at the Danish1.54~m telescopes, at the European Southern Observatory (La Silla,Chile)
| 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.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| On the nature of the high-latitude B-type star CPD-61 deg455
High-resolution, high-signal-to-noise optical and near-infrared spectra,along with lower resolution infrared spectra, of the high-latitude,faint B-type star CPD-61 deg455 have been obtained using the 3.9-mAnglo-Australian Telescope. Using LTE model atmosphere codes to computeoptical absorption profiles in the hot star, we find atmosphericparameters of T_eff=25000k and logg~3.6 furthermore, the abundancepattern of metals as measured differentially with respect to theGalactic disc B-type star xi^1CMa is not that expected for a normalyoung object. We show that the previous interpretation of this object asa composite consisting of a B-type star with a possible early K-typegiant secondary is consistent with the near-infrared and infrared data.We hypothesize that CPD-61 deg455 is in fact an evolved, post-asymptoticgiant branch (post-AGB) star in a binary system, and is possibly ahotter analogue of the binary systems containing younger, coolerpost-AGB stars discussed by van Winckel, Waelkens & Waters.
| The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
| Kinematics of metal-poor stars in the galaxy
We discuss the kinematic properties of a sample of 1936 Galactic stars,selected without kinematic bias, and with abundances (Fe/H) is less thanor equal to -0.6. The stars selected for this study all have measuredradial velocities, and the majority have abundances determined fromspectroscopic or narrow-/intermediate-band photometric techniques. Incontrast to previous examinations of the kinematics of the metal-poorstars in the Galaxy, our sample contains large numbers of stars that arelocated at distances in excess of 1 kpc from the Galactic plane. Thus, amuch clearer picture of the nature of the metal-deficient populations inthe Galaxy can now be drawn.
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Evolved GK stars near the Sun. 2: The young disk population
From a sample of nearly 2000 GK giants a group of young disk stars withwell determined space motions has been selected. The zero point of theluminosity calibrations, both from the ultraviolet flux (modifiedStroemgren system) and that in the region of 4200 to 4900 A (DDOsystem), show a discontinuity of about a half magnitude at the border ofthe young disk and old disk domains. The population separation is basedon the space velocity components, which are also an age discriminant,with the population interface near 2 x 109 yr, based onmodels with convective overshoot at the core. This age corresponds togiant masses near 1.7 solar mass, near the critical mass separating theyoung stars that do not burn helium in degenerate cores from older starsthat do. Ten percent of both populations show CN anomalies in that thederived value of P(Fe/H) from CN (Cm) and fromFe(M1) differ by more than 0.1 dex and the weak and strong CNstars occur equally in the old disk but the weak CN stars predominate inthe young disk. Peculiar stars, where flux distortions affect theluminosity calibrations, are of the CH+(Ba II) and CH-(weak G band)variety and represent less than 1% of the stars in both populations. Theyoung disk giants are restricted to ages greater than about109 yr, because younger stars are bright giants orsupergiants (luminosity class 2 or 1), and younger than about 2 x109 yr, because the old disk-young disk boundary occurs near1.7 solar mass. The distribution of heavy element abundances, P(Fe/H),for young disk giants is both more limited in range (+/- 0.4 dex) and isskewed toward higher abundances, compared with the nearly normaldistribution for old disk giants. The distribution of (U,V) velocityvectors gives (U,V,W) and their dispersions = (+17.6 +/- 18.4, -14.8 +/-8.4, -6.9 +/- 13.0) and (+3.6 +/- 38.4, -20.7 +/- 27.5, -6.7 +/-17.3)km/s for young and old disk giants, respectively.
| Further Determinations of the Gravities of Cool Giant Stars Using MGI and MGH Features
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.264..334B&db_key=AST
| Optical Polarization of 1000 Stars Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..551L&db_key=AST
| Spectroscopic investigation of cool giants and the authenticity of their reported microwave emission
Surface velocities and metal abundances for 19 red giant stars in thespectral range G5 to M3 are derived on the basis of AAT echellespectroscopy data. Attention is given to the question of whether thestars reported to emit radio bursts had different physical properties(rotation rate, macroturbulence, microturbulence, and metal abundance)from those without the radio bursts, which might explain why they wereradio emitters. The various velocities had values consistent with thosepreviously found for other similar stars. There was an observed increasein both macroturbulent and, less definitely, microturbulent velocitieswith lateness of spectral type at K3 and later. A weak correlationbetween surface velocities and 8.4-GHz radio surface fluxes was found.No connection between iron abundances and radio surface fluxes wasdetected. It is concluded that few, if any, of the cool giants are radioemitters.
| UBV(RI)c observations for 13 bright Cepheids
Photometry in the UBV(RI)c system has been obtained for 13 of thebrightest Cepheids in the southern sky available to the new SydneyUniversity Stellar Interferometer. The stars observed were Eta Aq1, 1Car, U Car, AX Cir, Beta Dor, Zeta Gem, T Mon, Kappa Pav, U Sgr, W Sgr,X Sgr, Y Sgr, and AH Vel. The main purpose of the photometry is toprovide current epoch data for the phases of the variables, although forseveral of the stars these data are also the first in the (RI)c system.
| Non-thermal radio emission from post-main-sequence stars
The Australia Telescope Compact Array (ATCA) has been used to make4.8-GHz observations of 24 fields containing post-main-sequence stars.These stars were selected from a sample of late-type (spectral types G,K and M) giants and bright giants within 30 pc claimed by Slee et al.,from observations with the Parkes radio telescope, to be variablenon-thermal radio emitters. No significant 4.8-GHz radio emission wasdetected from these stars. Non-detection of any stars with the ATCA isan improbable result, and calls for a re-analysis of the original Parkes8.4-GHz observations. A re-analysis suggests that the majority of theclaimed Parkes detections with S less than about 8 mJy are false. Thefive claimed Parkes detections with S greater than 8 mJy are discussedindividually on the basis of the ATCA and Molonglo Observatory SynthesisTelescope (MOST) observations. It is concluded that the Parkes, ATCA,and MOST observations do not invalidate the concept of a 'coronalboundary line' between stars exhibiting chromospheric and coronalemission, and more evolved stars displaying only cool winds.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Karina |
| Sað Açýklýk: | 10h53m29.60s |
| Yükselim: | -58°51'12.0" |
| Görünürdeki Parlaklýk: | 3.78 |
| Uzaklýk: | 29.665 parsek |
| özdevim Sað Açýklýk: | 78.8 |
| özdevim Yükselim: | 37.5 |
| B-T magnitude: | 4.951 |
| V-T magnitude: | 3.882 |
Kataloglar ve belirtme:
|
