Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Galactic abundance gradients from Cepheids. On the iron abundance gradient around 10-12 kpc
Context: Classical Cepheids are excellent tracers of intermediate-massstars, since their distances can be estimated with very high accuracy.In particular, they can be adopted to trace the chemical evolution ofthe Galactic disk. Aims: Homogeneous iron abundance measurements for 33Galactic Cepheids located in the outer disk together with accuratedistance determinations based on near-infrared photometry are adopted toconstrain the Galactic iron gradient beyond 10 kpc. Methods: Ironabundances were determined using high resolution Cepheid spectracollected with three different observational instruments: ESPaDOnS@CFHT,Narval@TBL and FEROS@2.2m ESO/MPG telescope. Cepheid distances wereestimated using near-infrared (J,H,K-band) period-luminosity relationsand data from SAAO and the 2MASS catalog. Results: The least squaressolution over the entire data set indicates that the iron gradient inthe Galactic disk presents a slope of -0.052±0.003 textrm {dexkpc}-1 in the 5-17 kpc range. However, the change of the ironabundance across the disk seems to be better described by a linearregime inside the solar circle and a flattening of the gradient towardthe outer disk (beyond 10 kpc). In the latter region the iron gradientpresents a shallower slope, i.e. -0.012±0.014 textrm {dexkpc}-1. In the outer disk (10-12 kpc) we also found thatCepheids present an increase in the spread in iron abundance. Currentevidence indicates that the spread in metallicity depends on theGalactocentric longitude. Finally, current data do not support thehypothesis of a discontinuity in the iron gradient at Galactocentricdistances of 10-12 kpc. Conclusions: The occurrence of a spread in ironabundance as a function of the Galactocentric longitude indicates thatlinear radial gradients should be cautiously treated to constrain thechemical evolution across the disk.
| Baade-Wesselink distances and the effect of metallicity in classical cepheids
Context: The metallicity dependence of the Cepheid PL-relation is ofimportance in establishing the extra-galactic distance scale. Aims: Theaim of this paper is to investigate the metallicity dependence of thePL-relation in V and K based on a sample of 68 Galactic Cepheids withindividual Baade-Wesselink distances (some of the stars also have anHST-based parallax) and individually determined metallicities fromhigh-resolution spectroscopy. Methods: Literature values of the V-band,K-band and radial velocity data have been collected for a sample of 68classical cepheids that have their metallicity determined in theliterature from high-resolution spectroscopy. Based on a (V-K)surface-brightness relation and a projection factor derived in aprevious paper, distances have been derived from a Baade-Wesselinkanalysis. PL- and PLZ-relations in V and K are derived. Results: Theeffect of the adopted dependence of the projection factor on period isinvestigated. The change from a constant p-factor to one recentlysuggested in the literature with a mild dependence on log P results in aless steep slope by 0.1 unit, which is about the 1-sigma error bar inthe slope itself. The observed slope in the PL-relation in V in the LMCagrees with both hypotheses. In K the difference between the Galacticand LMC slope is larger and would favour a mild period dependence of thep-factor. The dependence on metallicity in V and K is found to bemarginal, and independent of the choice of p-factor on period. Thisresult is severely limited by the small range in metallicity covered bythe Galactic Cepheids.
| A new calibration of Galactic Cepheid period-luminosity relations from B to K bands, and a comparison to LMC relations
Context: The universality of the Cepheid period-luminosity (PL)relations has been under discussion since metallicity effects wereassumed to play a role in the value of the intercept and, more recently,of the slope of these relations. Aims: The goal of the present study isto calibrate the Galactic PL relations in various photometric bands(from B to K) and to compare the results to the well-established PLrelations in the LMC. Methods: We use a set of 59 calibrating stars,the distances of which are measured using five different distanceindicators: Hubble Space Telescope and revised Hipparcos parallaxes,infrared surface brightness and interferometric Baade-Wesselinkparallaxes, and classical Zero-Age-Main-Sequence-fitting parallaxes forCepheids belonging to open clusters or OB stars associations. A detaileddiscussion of absorption corrections and projection factor to be used isgiven. Results: We find no significant difference in the slopes of thePL relations between LMC and our Galaxy. Conclusions: We conclude thatthe Cepheid PL relations have universal slopes in all photometric bands,not depending on the galaxy under study (at least for LMC and MilkyWay). The possible zero-point variation with metal content is notdiscussed in the present work, but an upper limit of 18.50 for the LMCdistance modulus can be deduced from our data.Tables 2, 6 and 7 are only available in electronic form athttp://www.aanda.org
| New homogeneous iron abundances of double-mode Cepheids from high-resolution echelle spectroscopy
Aims.We define the relationship between the double-mode pulsation ofCepheids and metallicity in a more accurate way, determine the empiricalmetallicities of double-mode Cepheids from homogeneous, high-resolutionspectroscopic data, and study of the period-ratio - metallicitydependence. Methods: The high S/N echelle spectra obtained with theFEROS spectrograph were analyzed using a self-developed IRAF script, andthe iron abundances were determined by comparing with synthetic spectraassuming LTE. Results: Accurate [Fe/H] values of 17 galactic beatCepheids were determined. All these stars have solar or slightlysubsolar metallicity. Their period ratio (P1 / P_0) showsstrong correlation with their derived [Fe/H] values. The correspondingperiod ratio - metallicity relation has been evaluated.Based on observations taken with the ESO 2.2-m telescope at La Silla,Chile (Proposal 073.D-0072) and the 1.82 m telescope at David DunlapObservatory, Canada.
| Cepheid parallaxes and the Hubble constant
Revised Hipparcos parallaxes for classical Cepheids are analysedtogether with 10 Hubble Space Telescope (HST)-based parallaxes. In areddening-free V, I relation we find that the coefficient of logP is thesame within the uncertainties in our Galaxy as in the Large MagellanicCloud (LMC), contrary to some previous suggestions. Cepheids in theinner region of NGC4258 with near solar metallicities confirm thisresult. We obtain a zero-point for the reddening-free relation and applyit to the Cepheids in galaxies used by Sandage et al. to calibrate theabsolute magnitudes of Type Ia supernova (SNIa) and to derive the Hubbleconstant. We revise their result for H0 from 62 to 70 +/-5kms-1Mpc-1. The Freedman et al. value is revisedfrom 72 to 76 +/- 8kms-1Mpc-1. These results areinsensitive to Cepheid metallicity corrections. The Cepheids in theinner region of NGC4258 yield a modulus of 29.22 +/- 0.03 (int.)compared with a maser-based modulus of 29.29 +/- 0.15. Distance modulifor the LMC, uncorrected for any metallicity effects, are 18.52 +/- 0.03from a reddening-free relation in V, I; 18.47 +/- 0.03 from aperiod-luminosity relation at K; 18.45 +/- 0.04 from aperiod-luminosity-colour relation in J, K. Adopting a metallicitycorrection in V, I from Macri et al. leads to a true LMC modulus of18.39 +/- 0.05.
| The reliability of Cepheid reddenings based on BVIC photometry
Externally determined values of E(B - V) (Espacered) for 40Galactic Cepheids are compared to reddenings determined using B - V andV - IC colour indices and the method of Dean, Warren &Cousins (EBVIC), updated to allow for metallicitycorrections. With three stars omitted on the grounds of uncertainty intheir space reddenings, we find thatThe two scales agree well in scale and zero-point, and there is nosignificant trend with period. Given the non-zero errors in the Cepheidspace reddenings, the estimated error in BVIC Cepheidreddenings is no more than 0.02.The above results are not significantly changed whether one corrects thereddenings for metallicity using older Bell models, or using more recentmodels by Sandage, Bell & Tripicco. Using the SBT models to correctthe reddenings of Cloud Cepheids for metallicity gives slightly smallerreddenings at a given metal deficiency, yielding `new' median reddeningsof 0.056 (Small Magellanic Cloud) and 0.076 (Large Magellanic Cloud) ifwe assume the same metal deficiencies as Caldwell and Coulson. Withmetal deficiencies of [M/H] = -0.7 and -0.25, the median reddenings are0.040 and 0.058.
| Detailed chemical composition of Galactic Cepheids. A determination of the Galactic abundance gradient in the 8-12 kpc region
Aims.The recent introduction of high-resolution/large spectral-rangespectrographs has provided the opportunity to investigate the chemicalcomposition of classical Cepheids in detail. This paper focusses on newabundance determinations for iron and 6 light metals (O, Na, Mg, Al, Si,Ca) in 30 Galactic Cepheids. We also give a new estimate of the Galacticradial abundance gradient. Methods: The stellar effective temperatureswere determined using the method of line depth ratios, and the surfacegravity and the microturbulent velocity vt by imposing theionization balance between Fe I and Fe II with the help of curves ofgrowth. Abundances were calculated with classical LTE atmosphere models. Results: Abundances were obtained with rms accuracies of about0.05-0.10 dex for Fe, and 0.05-0.20 dex for the other elements. Cepheidsin our sample have solar-like abundances, and current measurements agreequite well with previous determinations. We computed "single zone"Galactic radial abundance gradients for the 8-12 kpc region and found aslope for iron of -0.061 dex kpc-1.Based on observations made with the 1.52 m ESO Telescope at La Silla,Chile.
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| Improvement of the CORS method for Cepheids radii determination based on Strömgren photometry
In this paper we present a modified version of the CORS method based ona new calibration of the Surface Brightness function in theStrömgren photometric system. The method has been tested by meansof synthetic light and radial velocity curves derived from nonlinearpulsation models. Detailed simulations have been performed to take intoaccount the quality of real observed curves as well as possible shiftsbetween photometric and radial velocity data. The method has been thenapplied to a sample of Galactic Cepheids with Strömgren photometryand radial velocity data to derive the radii and a new PR relation. As aresult we find log R = (1.19 ± 0.09) + (0.74 ± 0.11) logP (rms = 0.07). The comparison between our result and previous estimatesin the literature is satisfactory. Better results are expected from theadoption of improved model atmosphere grids.
| A new Period-Radius relation for Galactic Classical Cepheids
We discuss a new Period-Radius (PR) relation for Galactic ClassicalCepheids, obtained by means of a new version of the CORS method whichhas been modified in order to be run with the Strömgren photometricsystem. The major change consists in the calibration of the SurfaceBrightness as a function of the two ``reddening free'' colourindexes [c1] and [m1], by means of the model atmospheres by Castelli etal. (1997). In this contribution we first briefly discuss somenumerical experiments performed on the basis of synthetic Cepheid lightcurves to test the accuracy of the method, and then report thePeriod-Radius relation for Classical Cepheids obtained by applying thethe new method to a sample of Galactic Cepheids.
| Sodium enrichment of the stellar atmospheres. II. Galactic Cepheids
The present paper is a continuation of our study of the sodium abundancein supergiant atmospheres (Andrievsky et al. 2002a). We present theresults on the NLTE abundance determination in Cepheids, and the derivedrelation between the sodium overabundance and their masses.
| A Revised Calibration of the MV-W(O I 7774) Relationship using Hipparcos Data: Its Application to Cepheids and Evolved Stars
A new calibration of the MV-W(O I 7774) relationship hasbeen calculated using better reddening and distance estimates for asample of 27 calibrator stars of spectral types A to G, based onaccurate parallaxes and proper motions from the Hipparcos and Tychocatalogues. The present calibration predicts absolute magnitude withaccuracies of +/-0.38mag for a sample covering a large range ofMV, from -9.5 to +0.35 mag. The color term included in aprevious paper has been dropped since its inclusion does not lead to anysignificant improvement in the calibration. The variation of the O I7774 feature in the classical cepheid SS Sct has been studied. Wecalculated a phase-dependent correction to random phase OI featurestrengths in Cepheids, such that it predicts mean absolute magnitudesusing the above calibration. After applying such a correction, we couldincrease the list of calibrators to 58 by adding MV and O Itriplet strength data for 31 classical Cepheids. The standard error ofthe calibration using the composite sample was comparable to thatobtained from the primary 27 calibrators, showing that it is possible tocalculate mean Cepheid luminosities from random phase observations ofthe O I 7774 feature. We use our derived calibrations to estimateMV for a set of evolved objects to be able to locate theirpositions in the HR diagram.
| Using Cepheids to determine the galactic abundance gradient. I. The solar neighbourhood
A number of studies of abundance gradients in the galactic disk havebeen performed in recent years. The results obtained are ratherdisparate: from no detectable gradient to a rather significant slope ofabout -0.1 dex kpc-1. The present study concerns theabundance gradient based on the spectroscopic analysis of a sample ofclassical Cepheids. These stars enable one to obtain reliable abundancesof a variety of chemical elements. Additionally, they have welldetermined distances which allow an accurate determination of abundancedistributions in the galactic disc. Using 236 high resolution spectra of77 galactic Cepheids, the radial elemental distribution in the galacticdisc between galactocentric distances in the range 6-11 kpc has beeninvestigated. Gradients for 25 chemical elements (from carbon togadolinium) are derived. The following results were obtained in thisstudy. Almost all investigated elements show rather flat abundancedistributions in the middle part of galactic disc. Typical values foriron-group elements lie within an interval from ~-0.02 to ~-0.04 dexkpc-1 (in particular, for iron we obtainedd[Fe/H]/dRG =-0.029 dex kpc-1). Similar gradientswere also obtained for O, Mg, Al, Si, and Ca. For sulphur we have founda steeper gradient (-0.05 dex kpc-1). For elements from Zr toGd we obtained (within the error bars) a near to zero gradient value.This result is reported for the first time. Those elements whoseabundance is not expected to be altered during the early stellarevolution (e.g. the iron-group elements) show at the solargalactocentric distance [El/H] values which are essentially solar.Therefore, there is no apparent reason to consider our Sun as ametal-rich star. The gradient values obtained in the present studyindicate that the radial abundance distribution within 6-11 kpc is quitehomogeneous, and this result favors a galactic model including a barstructure which may induce radial flows in the disc, and thus may beresponsible for abundance homogenization. Based on spectra collected atMcDonald - USA, SAORAS - Russia, KPNO - USA, CTIO - Chile, MSO -Australia, OHP - France. Full Table 1 is only available in electronicform at http://www.edpsciences.org Table A1 (Appendix) is only, andTable 2 also, available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/32
| 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
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| An Inquest of Non-Linear Pulsations in BQ Serpens and VX Puppis
We present analysis of two double mode Cepheid variable stars, BQSerpens and VX Puppis. Observations were obtained using Johnson UVBRIphotometry with the Four College Consortium's (FCCAPT) AutomaticPhotometric Telescope. Performing Fourier exapansion, we have refinedthe fundamental frequency of pulsation for BQ Serpens to be 0.2341 c/dand the first overtone to 0.3320 c/d. For VX Puppis, the fundamentalfrequency and first overtone are 0.3320 c/d and 0.4674 c/d,respectively. Decomposing the variation to both the fundamental andfirst overtone exposes non-linear coupling terms. Here, we calculate thedistribution of energy among these various modes of interaction based onPardo and Poretti's analysis of the double mode Cepheid TU CAS. Thisresearch is funded by NSF Grants #AST86-16362,\ #AST91-15114,#AST95-28906, and #AST-0071260 to the College of Charleston
| Masses for Galactic Beat Cepheids
Accurate mass determinations for Cepheids may be used to determine thedegree of excess mixing in the interiors of their main-sequenceprogenitors: the larger the excess mixing, the larger the luminosity ofthe Cepheid of a given mass, or the smaller the mass of a Cepheid withgiven luminosity. Dynamical masses determined recently for a few Cepheidbinaries indicate excess mixing somewhat stronger than thatcorresponding to the convective overshoot models by Schaller et al. BeatCepheids can be used similarly to test main-sequence mixing in stellarinteriors. The period ratios for beat Cepheids depend on luminosity,Teff, heavy element abundance, and mass. By comparingpulsational models and the observationally derived luminosity,Teff, metallicities, and period ratios it is possible toobtain masses for these stars, the so-called beat masses. With the oldopacities masses much smaller than the evolutionary masses wereobtained. With the new OPAL opacities a beat mass close to the dynamicalmass was obtained for the binary beat Cepheid Y Carinae, showing that itis now possible to obtain reliable beat masses. In this paper, wedetermine beat masses for seven Galactic beat Cepheids for whichphotometric and spectroscopic data are available. We find an averagemass around 4.2+/-0.3 Msolar for these stars, though theactual error limits for each star may be larger mainly because ofuncertainties in E(B-V) and the heavy element abundances. (As derivedspectroscopically, beat Cepheids are in general metal-poor, with-0.4<~[Fe/H]<~0.0). The relation between the derived beat massesand the luminosities again indicates excess mixing that is somewhatlarger than that corresponding to the models by Schaller et al.
| 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.
| I- and JHK-band photometry of classical Cepheids in the HIPPARCOS catalog
By correlating the \cite[Fernie et al. (1995)]{F95} electronic databaseon Cepheids with the ``resolved variable catalog'' of the hipparcosmission and the simbad catalog one finds that there are 280 Cepheids inthe hipparcos catalog. By removing W Vir stars (Type ii Cepheids),double-mode Cepheids, Cepheids with an unreliable solution in thehipparcos catalog, and stars without photometry, it turns out that thereare 248 classical Cepheids left, of which 32 are classified asfirst-overtone pulsators. For these stars the literature was searchedfor I-band and near-infrared data. Intensity-mean I-band photometry onthe Cousins system is derived for 189 stars, and intensity-mean JHK dataon the Carter system is presented for 69 stars.
| The Radial Velocity of Double-mode Cepheid BD -10 4669
We present the first radial velocity measurements of the recentlydiscovered double-mode Cepheid BD
| UVBY beta Photometric Data and Fourier Coefficients for Galactic Population I and Population II Cepheids
Photometric data in the uvby beta system are presented for a sample of98 Population I Cepheids and seven W Virginis or Population II Cepheids.The importance of the Fourier decomposition technique in the study ofthe structure of pulsating stars is stressed. Mean values and Fourierdecomposition coefficients for the V, b - y, m1, and c1 variations arecalculated. Also, mean values of H beta are provided. New times ofmaximum V light are reported for the majority of the stars in thesample. Significant shifts of the light and color curves were found insome Cepheids; these are explained by their period variations. Thesestars are highlighted in the text.
| A catalog of Cepheid radial velocities measured in 1995-1998 with the correlation spectrometer.
Not Available
| 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
| The galactic double-mode Cepheids. II. Properties of the generalized phase differences.
By considering the least-squares fits of the double-mode Cepheid lightcurves discussed in Paper I we defined their properties by their Fourierparameters and generalized phase differences G_i,j_. When plotting thelatter quantities as a function of the order, the second order terms areconfined in the region just below 3π/2; the third order terms haveπ/2
| The galactic double-mode Cepheids. I. Frequency analysis of the light curves and comparison with single-mode Cepheids.
We submitted the available photometric V data of all the known galacticDouble Mode Cepheids (DMCs) to a careful frequency analysis with the aimof detecting in each case the importance of the harmonics and of thecross coupling terms. For each object, starting from different datasubsets, we progressively built a homogenous set of data, checking theconsistency of the results step by step. It was demonstrated that eachstar displays a different content, showing that no a priori fit can beapplied. Up to 4 harmonics were found for the fundamental radial mode(F); in every case, 2 harmonics were found for the first overtone radialmode (1O). We also proceeded to a preliminar analysis of the Fourierparameters of the DMC light curves and we found a very close similaritybetween i) the light curves of the classical Cepheids and those of theF-mode of the DMCs; ii) the light curves of the s-Cepheids and those ofthe 1O-mode of the DMCs. The analysis of DMC light curves offers thepossibility of unifying the light curves of classical and s-Cepheids.The case of the unique DMC CO Aur is also discussed.
| Radial Velocity Curves and First Calculations of the Radii for Four Double-mode Cepheids
Not Available
| Parameters of the JHK light curves of classical Cepheids and the interstellar-extinction LAW.
Not Available
| A catalog of Cepheid radial velocities measured in 1992-1995 with a correlation spectrometer.
Not Available
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Yilan |
| Sað Açýklýk: | 18h36m15.94s |
| Yükselim: | +04°23'53.7" |
| Görünürdeki Parlaklýk: | 9.533 |
| özdevim Sað Açýklýk: | 4 |
| özdevim Yükselim: | 1.7 |
| B-T magnitude: | 11.31 |
| V-T magnitude: | 9.68 |
Kataloglar ve belirtme:
|
