Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Spectroscopic binary orbits from photoelectric radial velocities. Paper 180: zeta Aurigae
Not Available
| VLA Observations of ζ Aurigae: Confirmation of the Slow Acceleration Wind Density Structure
Studies of the winds from single K and early M evolved stars indicatethat these flows typically reach a significant fraction of theirterminal velocity within the first couple of stellar radii. The mostdetailed spatially resolved information of the extended atmospheres ofthese spectral types comes from the ζ Aur eclipsing binaries.However, the wind acceleration inferred for the evolved primaries inthese systems appears significantly slower than for stars of similarspectral type. Since there are no successful theories for mass loss fromK and early M evolved stars, it is important to place strong empiricalconstraints on potential models and determine whether this difference inacceleration is real or an artifact of the analyses. We have undertakena radio continuum monitoring study of ζ Aurigae (K4 Ib + B5 V)using the Very Large Array to test the wind density model of Baade etal. that is based on Hubble Space Telescope (HST) Goddard HighResolution Spectrograph ultraviolet spectra. ζ Aur was monitored atcentimeter wavelengths over a complete orbital cycle, and fluxvariations during the orbit are found to be of similar magnitude tovariations at similar orbital phases in the adjacent orbit. Duringeclipse, the flux does not decrease, showing that the radio emissionoriginates from a volume substantially larger thanR3K~(150Rsolar)3 surroundingthe B star. Using the one-dimensional density model of the K4 Ibprimary's wind derived from HST spectral line profile modeling andelectron temperature estimates from previous optical and new HSTstudies, we find that the predicted radio fluxes are consistent withthose observed. Three-dimensional hydrodynamic simulations indicate thatthe accretion flow perturbations near the B star do not contributesignificantly to the total radio flux from the system, consistent withthe radio eclipse observations. Our radio observations confirm the slowwind acceleration for the evolved K4 Ib component. ζ Aur's velocitystructure does not appear to be typical of single stars with similarspectral types. This highlights the need for more comprehensivemultiwavelength studies for both single stars, which have been sadlyneglected, and other ζ Aur systems to determine if its windproperties are typical.
| 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
| 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}
| BD +59°224: A New ζ Aurigae System
The star BD +59°224 has an interesting history of spectroscopicclassification, having been described in the literature variously as acomposite G- and F-type star with helium, a K5 star, an O-type star, andan emission-line object similar to a planetary nebula. We present newspectra of this object that clearly show the star to be a binary with aK4.5 Ib primary and a B3 V secondary. We also calculate a reddening anddistance [E(B-V)~0.75, d~2.1 kpc] and point out similarities betweenthis object and the class of ζ Aurigae stars.
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 175: BD+48 1048, HR 1736, HR 3416, and HD 199378/9
Not Available
| Improved Baade-Wesselink surface brightness relations
Recent, and older accurate, data on (limb-darkened) angular diameters iscompiled for 221 stars, as well as BVRIJK[12][25] magnitudes for thoseobjects, when available. Nine stars (all M-giants or supergiants)showing excess in the [12-25] colour are excluded from the analysis asthis may indicate the presence of dust influencing the optical andnear-infrared colours as well. Based on this large sample,Baade-Wesselink surface brightness (SB) relations are presented fordwarfs, giants, supergiants and dwarfs in the optical and near-infrared.M-giants are found to follow different SB relations from non-M-giants,in particular in V versus V-R. The preferred relation for non-M-giantsis compared to the earlier relation by Fouqué and Gieren (basedon 10 stars) and Nordgren et al. (based on 57 stars). Increasing thesample size does not lead to a lower rms value. It is shown that theresiduals do not correlate with metallicity at a significant level. Thefinally adopted observed angular diameters are compared to thosepredicted by Cohen et al. for 45 stars in common, and there isreasonable overall, and good agreement when θ < 6 mas.Finally, I comment on the common practice in the literature to average,and then fix, the zero-point of the V versus V-K, V versus V-R and Kversus J-K relations, and then rederive the slopes. Such a commonzero-point at zero colour is not expected from model atmospheres for theV-R colour and depends on gravity. Relations derived in this way may bebiased.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| NLTE Radiative Transfer in the Extended Atmospheres and Winds of Cool Stars
Not Available
| Angular Diameters of Stars from the Mark III Optical Interferometer
Observations of 85 stars were obtained at wavelengths between 451 and800 nm with the Mark III Stellar Interferometer on Mount Wilson, nearPasadena, California. Angular diameters were determined by fitting auniform-disk model to the visibility amplitude versus projected baselinelength. Half the angular diameters determined at 800 nm have formalerrors smaller than 1%. Limb-darkened angular diameters, effectivetemperatures, and surface brightnesses were determined for these stars,and relationships between these parameters are presented. Scatter inthese relationships is larger than would be expected from themeasurement uncertainties. We argue that this scatter is not due to anunderestimate of the angular diameter errors; whether it is due tophotometric errors or is intrinsic to the relationship is unresolved.The agreement with other observations of the same stars at the samewavelengths is good; the width of the difference distribution iscomparable to that estimated from the error bars, but the wings of thedistribution are larger than Gaussian. Comparison with infraredmeasurements is more problematic; in disagreement with models, coolerstars appear systematically smaller in the near-infrared than expected,warmer stars larger.
| Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components.
A sample of 135 stars with composite spectra has been observed in thenear-UV spectral region with the Aurélie spectrograph at theObservatoire de Haute-Provence. Using the spectral classifications ofthe cool components previously determined with near infrared spectra, weobtained reliable spectral types of the hot components of the samplesystems. The hot components were isolated by the subtraction methodusing MK standards as surrogates of the cool components. We also derivedthe visual magnitude differences between the components usingWillstrop's normalized stellar flux ratios. We propose a photometricmodel for each of these systems on the basis of our spectroscopic dataand the Hipparcos data. We bring to light a discrepancy for the Gsupergiant primaries between the visual absolute magnitudes deduced fromHipparcos parallaxes and those tabulated by Schmidt-Kaler for the GIbstars: we propose a scale of Mv-values for these stars incomposite systems. By way of statistics, about 75% of the hot componentsare dwarf or subgiant stars, and 25% should be giants. The distributionin spectral types is as follows: 41% of B-type components, 57% of typeA, and 2% of type F; 68% of the hot components have a spectral type inthe range B7 to A2. The distribution of the ΔMv-valuesshows a maximum near 0.75 mag.
| Speckle Observations of Composite Spectrum Stars with PISCO in 1993-1998
We present speckle interferometry observations of 47 composite spectrumstars obtained between 1993 and 1998 at the Pic du Midi Observatory withthe PISCO speckle camera. 76% of over 150 independent 10 minutesequences of observations led to a companion detection. Binary componentangular separations ranged from 0.05" to 1.2". We also obtained a seriesof 23 measurements of an additional nine close binaries. PISCOobservations confirm, for the first time since their discovery, theduplicity of HD 29104 (L4), HD 83808 (WGT 1Aa), HD 183912 Aa' (BON Ap),and HD 156729 (HR 6436). Discovered as double by Hipparcos, theparticularly difficult to resolve HD 156729 was observed despite thelarge magnitude difference, Δm=4.2, between its two components.Based on observations made with the Télescope Bernard Lyot at Picdu Midi Observatory, France.
| Envelope Ejection: An Alternative Evolutionary Process for Some Early Case B Binaries
We discuss the evolution of binaries with moderately high masses (~10-30Msolar) and with periods of ~3-300 days, corresponding mostlyto early case B. These are usually thought to evolve either byreasonably conservative Roche lobe overflow, if the initial mass ratiois fairly mild, or else by highly nonconservative common-envelopeevolution, with spiral-in to short periods (hours, typically), if theinitial mass ratio is rather extreme. We discuss here a handful ofbinaries from part of this period range (~50-250 days), which appear tohave followed a different path: we argue that they must have lost alarge proportion of initial mass (~70%-80%) but without shortening theirperiods at all. We suggest that their behavior may be due to the factthat stars of such masses, when evolved also to rather large radii, arenot far from the Humphreys-Davidson limit, where single stars lose theirenvelopes spontaneously in P Cygni winds, and so have envelopes that areonly lightly bound to the core. These envelopes therefore may berelatively easily dissipated by the perturbing effect of a companion. Inaddition, some or all of the stars considered here may have been closeto the Cepheid instability strip when they filled their Roche lobes. Oneor the other, or both, of high luminosity and Cepheid instability, incombination with an appropriately close binary companion, may beimplicated.
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| A Large Spectral Class Dependence of the Wilson-Bappu Effect among Luminous Stars
The striking correlation between Ca II K-line emission width andabsolute visual magnitude has not previously been well calibrated forstars more luminous than giants. From a sample of binary systems fit toisochrones, we find deviations of more than 2 mag, correlated withspectral class, between these binarity Mv values and theWilson-Bappu relation. Additional Mv values derived fromHipparcos parallaxes are used to explore the systematics. The spectralclass dependence vanishes for K-line parameterlogW0<=1.80. Linear spectral class corrections are derivedfor the more luminous stars, with logW0>=2.00, while atable is provided for the transition region. The dispersion from theserelations is about +/-0.6 mag. This recalibration extends thedemonstrated applicability of the Wilson-Bappu technique toMv~=-5 or distance ~20 kpc.
| Comparison of Stellar Angular Diameters from the NPOI, the Mark III Optical Interferometer, and the Infrared Flux Method
The Navy Prototype Optical Interferometer (NPOI) has been used tomeasure the angular diameters of 41 late-type giant and supergiant starspreviously observed with the Mark III optical interferometer. Sixteen ofthese stars have published angular diameters based on model atmospheres(infrared flux method, IRFM). Comparison of these angular diametersshows that there are no systematic offsets between any pair of datasets. Furthermore, the reported uncertainties in the angular diametersmeasured using both interferometers are consistent with the distributionof the differences in the diameters. The distribution of diameterdifferences between the interferometric and model atmosphere angulardiameters are consistent with uncertainties in the IRFM diameters of1.4%. Although large differences in angular diameter measurements areseen for three stars, the data are insufficient to determine whetherthese differences are due to problems with the observations or are dueto temporal changes in the stellar diameters themselves.
| 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 proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
| The Ultraviolet Spectrum of VV Cephei Out of Eclipse
The International Ultraviolet Explorer (IUE) satellite observed VVCephei (M2 Iab+B?) over nearly a full 20.3 year orbital period, but allthe observations were obtained outside total eclipse. Egress of thechromospheric eclipse was the only portion of the eclipse observed byIUE. We have examined all 124 high-resolution IUE spectra of VV Cepheiand describe the spectrum and its variations. Contrary to initialexpectations, the spectrum remained complex throughout the entire orbit,and five line components have been identified: (1) emission lines; (2)neutral, low-excitation (e.g., Fe I) lines, which disappear as the hotcomponent emerges from eclipse; (3) broad, high-ionization (e.g., Si IVand Fe III) lines arising from the hot component or nearby circumstellarmaterial; (4) narrow absorption cores from the circumstellar envelope ofthe M supergiant; and (5) ``shell'' absorption lines with variableprofiles which do not absorb below a minimum depth. Mg II h and kemission broadens and strengthens when the system is near periastron andsecondary eclipse. Most of the variation in the other emission featuresappears to be stochastic rather than phase dependent. The continuumshows rapid variations on timescales as short as 2 weeks. At any onetime, the continuum flux between 1400 and 3000 Å is fairlyconstant but varies, apparently stochastically, in the range(2-7)x10-12 ergs s-1 cm-2Å-1 for observations obtained outside of chromosphericeclipse. The dereddened continuum fluxes vary as~λ-0.8, implying that the source is not purelystellar. Radial velocity measurements of the circumstellar and shelllines show that neither follows the radial velocity curve of the twostars. Circumstellar line velocities range from the systemic velocity to~15 km s-1 more negative, consistent with their formation inan extended circumstellar envelope of the M supergiant which is largecompared to the scale of the orbit. The shell lines are redshifted fromthe systemic velocity by ~30 km s-1. The last IUEobservations (near phase 0.9) showed shell lines with greater redshiftsand deeper absorption than around the rest of the cycle. The ultravioletspectrum of VV Cep is compared to spectra of stars showing similarfeatures: the Be shell star 28 Tauri, the B[e] star HD 45677, and the Msupergiant+B binary systems α Scorpii and KQ Puppis. A tabledetailing the appearance and behavior of numerous line multiplets ispresented.
| The intermediate-band approach to the surface-brightness method for Cepheid radii and distance determination
The surface-brightness parameter Fν is calibrated in termsof the Strömgren intermediate-band colour b-y. The relationFν-(b-y)o valid for Cepheids is calibratedusing accurate near-infrared radii and distances for selected Cepheids.We have obtained uvby photometry for non-Cepheid giant and supergiantstars with known angular diameters and compared the slope and zero-pointof their Fν-(b-y)o relation with the Cepheidcalibration. We found that the two calibrations are significantlydifferent. The theoretical models lie in between the two calibrations.It is remarked that Fν-colour relations derived fromnon-Cepheids and involving blue colours (e.g. B-V or b-y) are notapplicable to Cepheids, while those involving redder colours (e.g. V-R,V-K or V-J) also produce good radii for Cepheids. Selected Cepheids ascalibrators lead to the accurate relationFν=3.898(+/-0.003)-0.378(+/-0.006)(b-y)o, whichallowed the calculation of radii and distances for a sample of 59Galactic Cepheids. The uncertainties in the zero-point and slope of theabove relation are similar to those obtained from near-infrared colours,and determine the accuracies in radii and distance calculations. Whileinfrared light and colour curves for Cepheids may be superior inprecision, the intermediate-band b-y colour allows the recovery of meanradii with an accuracy comparable to those obtained from the infraredsolutions. The derived distances are consistent within the uncertaintieswith those predicted by a widely accepted period-luminosityrelationship. Likewise, the resulting period-radius relation from theintermediate-band approach is in better agreement with infrared versionsthan with optical versions of this law. It is highlighted that theintermediate-band calibration of the surface-brightness method in thiswork is of comparable accuracy to the near-infrared calibrations. Thepresent results stress the virtues of uvby in determining the physicalparameters of supergiant stars of intermediate temperature.
| Spectral Classification of Unresolved Binary Stars with Artificial Neural Networks
An artificial neural network technique has been developed to performtwo-dimensional spectral classification of the components of binarystars. The spectra are based on the 15 Å resolution near-infrared(NIR) spectral classification system described by Torres-Dodgen &Weaver. Using the spectrum with no manual intervention except wavelengthregistration, a single artificial neural network (ANN) can classifythese spectra with Morgan-Keenan types with an average accuracy of about2.5 types (subclasses) in temperature and about 0.45 classes inluminosity for up to 3 mag of difference in luminosity. The error intemperature classification does not increase substantially until thesecondary contributes less than 10% of the light of the system. Byfollowing the coarse-classification ANN with a specialist ANN, the meanabsolute errors are reduced to about 0.5 types in temperature and 0.33classes in luminosity. The resulting ANN network was applied to sevenbinary stars.
| A wind accretion wake in RW Hydrae?
RW Hydrae is an eclipsing detached binary star system, consisting of amass losing M-giant and a hot white dwarf on circular orbits. We analyzeUV observations of RW Hydrae. Approximately at phi = 0.78, clearlyunrelated to the primary eclipse, we detect in the UV light curve anevent with significantly reduced UV flux. The spectral characteristicsof this event indicate Rayleigh scattering due to a high column densityof neutral hydrogen in the line of sight to the hot white dwarf. Wemodel this observation in the framework of an accretion wake trailingthe white dwarf. This interpretation is analogous to comparable modelsfor zeta Aur systems and X-ray binaries. We find qualitative agreementbetween our 3D hydrodynamical accretion simulation and the observed UVlight curve of RW Hya. Based on observations with the InternationalUltraviolet Explorer and observations with the NASA/ESA Hubble SpaceTelescope, obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc. under NASA contract No. NAS5-26555.
| From OAO2 to HST. A quarter of a century of ultraviolet astronomy.
Not Available
| The Second Extreme Ultraviolet Explorer Right Angle Program Catalog
We present the detection of 235 extreme ultraviolet sources, of which169 are new detections, using the Extreme Ultraviolet Explorer's (EUVE)Right Angle Program (RAP) data. This catalog includes observations sincethe first EUVE RAP catalog (1994 January) and covers 17% of the sky. TheEUVE RAP uses the all-sky survey telescopes (also known as``scanners''), mounted at right angles to the Deep Survey andspectrometer instruments, to obtain photometric data in four wavelengthbands centered at ~100 Å (Lexan/B), ~200 Å (Al/Ti/C), ~400Å (Ti/Sb/Al), and ~550 Å (Sn/SiO). This allows the RAP toaccumulate data serendipitously during pointed spectroscopicobservations. The long exposure times possible with RAP observationsprovide much greater sensitivity than the all-sky survey. We presentEUVE source count rates and probable source identifications from theavailable catalogs and literature. The source distribution is similar toprevious extreme ultraviolet (EUV) catalogs with 2% early-type stars,45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no firmclassification, and 15% with no optical identification. We also present36 detections of early-type stars that are probably the result ofnon-EUV radiation. We have detected stellar flares from approximately 12sources, including: EUVE J0008+208, M4 star G32-6 (EUVE J0016+198), anew source EUVE J0202+105, EUVE J0213+368, RS CVn V711 Tau (EUVEJ0336+005), BY Draconis type variable V837 Tau (EUVE J0336+259), the newK5 binary EUVE J0725-004, EUVE J1147+050, EUVE J1148-374, EUVE J1334-083(EQ Vir), EUVE J1438-432 (WT 486/487), EUVE J1808+297, and the M5.5estar G208-45 (EUVE J1953+444). We present sample light curves for thebrighter sources.
| 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
| Spectral classifications in the near infrared of stars with composite spectra. III. Study of a sample of 137 objects with the Aurelie spectrograph
We provide spectral classifications for a sample of 137 stars mentionedas having composite spectra. The classifications were carried out on 33Angstroms /mm spectra in the region 8370 - 8870 Angstroms. Of these 137objects, 115 correspond in the infrared to cool stars (G, K or M) ofluminosity classes III, II and I; for 22 stars, we find only hot spectraof types B, A, F or Am, so that they do not fulfil our definition ofcomposite spectra. We detect four new Am stars, and one Am star (HD70826) turns out to be a composite spectrum object. As in Paper II, thecool components of composite spectra show a strong concentration in thevicinity of G8III. Based upon observations carried out at Observatoirede Haute-Provence (OHP).
| Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The Entire IUE Sample
We have obtained or retrieved IUE spectra for over 100 middle- andlate-type giant and supergiant stars whose spectra indicate the presenceof a hot component earlier than type F2. The hot companions areclassified accurately by temperature class from their far-UV spectra.The interstellar extinction of each system and the relative luminositiesof the components are derived from analysis of the UV and opticalfluxes, using a grid of UV intrinsic colors for hot dwarfs. We find thatthere is fair agreement in general between current UV spectralclassification and ground-based hot component types, in spite of thedifficulties of assigning the latter. There are a few cases in which thecool component optical classifications disagree considerably with thetemperature classes inferred from our analysis of UV and opticalphotometry. The extinction parameter agrees moderately well with otherdeterminations of B-V color excess. Many systems are worthy of furtherstudy especially to establish their spectroscopic orbits. Further workis planned to estimate luminosities of the cool components from the dataherein; in many cases, these luminosities' accuracies should becomparable to or exceed those of the Hipparcos parallaxes.
| Radii and effective temperatures for K and M giants and supergiants. II.
Not Available
| The rotation measurement of 12 late-type binaries.
Not Available
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Kugu |
| Sað Açýklýk: | 20h13m37.90s |
| Yükselim: | +46°44'29.0" |
| Görünürdeki Parlaklýk: | 3.79 |
| Uzaklýk: | 414.938 parsek |
| özdevim Sað Açýklýk: | 3.5 |
| özdevim Yükselim: | 3.3 |
| B-T magnitude: | 5.329 |
| V-T magnitude: | 3.929 |
Kataloglar ve belirtme:
|
INHABITED SKY
