Photometry of Type II Cepheids. III. The Intermediate-Period Stars
We present 741 new photometric observations for 22 Cepheids with periodsbetween 3 and 8 days. Many of the stars are probable type II Cepheids,but we have included some type I Cepheids for comparison. The shapes andstability of the shapes of the light curves, the stability of theperiods, and the scatter of individual data points are discussed.Although none of these proves to be a reliable discriminator betweentype I and type II Cepheids, they do permit the identification ofseveral unusual stars.
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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.
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The Spectra of Type II Cepheids. II. The Hα Line in Intermediate-Period Stars
We present 98 Hα profiles for 21 pulsating variable stars withperiods from 3 to 8 days. The strength, depth, and shape of Hαvary throughout the cycles of the stars in a way consistent with thetemperature changes. Otherwise, they are quite uniform among all thestars, with a single exception. In FM Del, Hα is weaker and has asmaller central depth than in the other stars. This and the wavelengthshifts of the core are attributed to incipient emission. Thedifferential velocity of Hα relative to the metal lines is lessthan 25 km s-1 for all the stars except QY Cyg, FM Del, andEF Tau. We suggest that this indicates that only these stars are type IICepheids despite the large distances of some of the others from theGalactic plane.Based in part on observations obtained with the Apache Point Observatory3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
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Two Period-Radius Relations for Classical Cepheids: Determining the Pulsation Mode and the Distance Scale
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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
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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
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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.
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Galactic Cepheids. Catalogue of light-curve parameters and distances
We report a new version of the catalogue of distances and light-curveparameters for Galactic classical Cepheids. The catalogue listsamplitudes, magnitudes at maximum light, and intensity means for 455stars in BVRI filters of the Johnson system and (RI)_C filters of theCron-Cousins system. The distances are based on our new multicolour setof PL relations and on our Cepheid-based solution for interstellarextinction law parameters and are referred to an LMC distance modulus of18.25. The catalogue is only available in electronic form at the CDS viaanonymous ftp (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Détermination des rayons de Céphéides. V. Vitesses radiales et dimensions de 22 Céphéides galactiques. Determination of the radii of Cepheids V. Radial velocities and dimensions of 22 galactic Cepheids
We present radial velocity data for 22 galactic Cepheid stars obtainedwith Coravel spectrometer. Continuous observation over several years hasenabled us to obtain 852 individual velocities covering all the phasesof the pulsation. The mean number of measurements per star is 39,ranging from 20 to 113. For each star radial velocity versus phasediagrams have been fitted by analytical relation, and the stellar radiusvariation has been derived by integration of this relation over thewhole period. Using recent ubv photometry of the literature and velocitycurves, we have calculated the radii of the stars using a method basedon the Baade-Wesselink concept. For these 22 Cepheids we give a linearlogarithmic period-radius relation with a range of 2,4 to 45 days. Lesobservations ont été effectuées àl'Observatoire de Haute-Provence (CNRS). Le tableau 1 est disponibleseulement sous forme électronique au CDS via ftp àcdsarc.u-strasbg.fr (130.79.128.5) ou viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Direct calibration of the Cepheid period-luminosity relation
After the first release of Hipparcos data, Feast & Catchpole gave anew value for the zero-point of the visual Cepheid period-luminosityrelation, based on trigonometric parallaxes. Because of the largeuncertainties on these parallaxes, the way in which individualmeasurements are weighted is of crucial importance. We thereforeconclude that the choice of the best weighting system can be aided by aMonte Carlo simulation. On the basis of such a simulation, it is shownthat (i) a cut-off in π or in σ_ππ introduces a strongbias; (ii) the zero-point is more stable when only the brightestCepheids are used; and (iii) the Feast & Catchpole weighting givesthe best zero-point and the lowest dispersion. After correction, theadopted visual period-luminosity relation is=-2.77logP-1.44+/-0.05. Moreover, we extend this study to thephotometric I band (Cousins) and obtain=-3.05logP-1.81+/-0.09.
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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.
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Monitoring Cepheid Period Changes From Saint Mary's University
CCD observations in blue light with the 0.4m telescope at Saint Mary'sUniversity are presented for the Cepheids SU Cyg, V402 Cyg, V1154 Cyg,V386 Cyg, V924 Cyg, MW Cyg, BB Her, GH Cyg, VY Cyg, TX Cyg, SZ Cyg, XCyg, CD Cyg, and CV Vul. The data are used to establish new times oflight maximum for the sample, and analyses of the new andpreviously-published O-C residuals are used to derive improved valuesfor the rates of period change for each program object. The new valuesagree closely with predictions from stellar evolutionary theory for therates at which intermediate-mass stars evolve through the Cepheidinstability strip, and provide an excellent means of establishing theinstability strip crossing mode for each variable.
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Spectroscopic survey of field Type II Cepheids
A sample of relatively bright, short- and intermediate-period (P=1-10d)Type II Cepheids in the Galactic field have been observedspectroscopically with an intermediate-resolution(lambda/Deltalambda=11000) spectrograph. The wavelength region was6500-6700A, including the Hα line and some photospheric ironlines. The signal-to-noise ratio (S/N) was usually between 50 and 100,depending on weather conditions and the brightness of target stars.Radial velocities were determined by cross-correlating the Cepheidspectra with those of selected IAU velocity standard stars having F-Gspectral types. The internal error of the velocity determination processwas calculated to be about 1 km s^-1. Hα emission and strong linesplitting were observed in BL Her during the expansion phase, but nosimilar phenomenon was detected in any other stars in this programme,except for AU Peg which has an unusual Hα line showing a PCygni-like profile. The velocity curve agrees well with recent CORAVELmeasurements. The velocity gradients in Cepheid atmospheres are studiedusing the Hα minus metallic velocities. Similar data are collectedfrom the literature. It seems that having large velocity differences(v_Hα-v_metal>40 km s^-1) is a characteristic feature of thevery short-period (P<1.5d) and longer period (P>10d) Cepheids.Between these period regions the Cepheid atmospheres exhibit smallervelocity differences. Most of the Type II Cepheids observed in thepresent study fall into this latter category. There might be a tendencyfor classical Cepheids of intermediate period to have larger maximumvelocity differences.
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A catalog of Cepheid radial velocities measured in 1995-1998 with the correlation spectrometer.
Not Available
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The radii of 62 classical Cepheids.
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Monitoring the Evolution of Cepheid Variables
Described here are preliminary results of a pilot project to monitorchanges in the ephemerides of northern hemisphere Cepheid's using anSBIG camera attached to the 0.4-m telescope of the campus obversatory atSaint Mary's University. Epochs of maximum light for fifteen Cepheid'shave been derived using published light curves for each variable astemplates, and the results are being used to update the O-C ephemeridesfor the program stars. Results for BB Her are presented here. Periodchanges for Cepheid variables are demonstrated to be an excellent meansof pinpointing their evolutionary status, as well as for investigatingother peculiarities of the class.
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Baade-Wesselink Radius Determination of Type II Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113.1833B&db_key=AST
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A catalog of Cepheid radial velocities measured in 1992-1995 with a correlation spectrometer.
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Mean radial velocities and binarity of Cepheids from 1987-1995 measurements.
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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.
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Rotation Curve of the System of Classical Cepheids and the Distance to the Galactic Center
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Catalog of radial velocities for northern Cepheids measured with a correlation spectrometer
A catalog containing 1446 individual radial velocity values for 79 fieldCepheids and three Cepheids in globular clusters, and 32 averaged radialvelocities of the Cepheid Alpha UMi derived from 100 individual velocityparameters is presented. A table of gamma velocities for 30 Cepheidswith sufficiently good coverage of Vr curves is included. Radialvelocity observations of CE Cas A and CF Cas, which are photometricmembers of the open cluster NGC 7790, made it possible to estimate theradial velocity of the cluster (-78.0 km/s).
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The SVS Numbering Series Discontinued
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Color Excesses on a Uniform Scale for 328 Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990ApJS...72..153F&db_key=AST
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The catalogue of light curves parameters, distances and space coordinates of classical Cepheids.
Not Available
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Structural properties of the light curves of s-Cepheids
Fourier decomposition of light curves of short period Cepheids ands-Cepheids has been performed in order to investigate the properties ofs-Cepheid light curves, compare them with those of classical Cepheidsand detect suspected overtone pulsators. In general, the low orderamplitude ratio and phase difference of s-Cepheid light curves aredifferent from those of classical Cepheids. In particular, thedistribution of phase difference values against the period indicates thepossible presence of two different trends separated by a discontinuitynear 3 days. This property has been interpreted tentatively as theeffect of a new type of resonance between pulsation modes. Among thestars taken into account in the present work, only IR Cep is a suspectedovertone pulsator.
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Population I pulsating stars. I - Period-luminosity (-colour) relations
Luminosities of Population I pulsating stars (Delta Scuti variables andclassical cepheids) are investigated. From data for 80 Delta Scutistars, semiempirical period-luminosity-color (P-L-C) relations andperiod-luminosity (P-L) relations are obtained for the four lowest modesof radial pulsations. The improvement of the accuracy of the stellarluminosity is determined when a P-L-C relation is used instead of thecorresponding P-L relation. From data for 155 classical cepheids,empirical P-L relations are derived for short-period stars, long-periodstars, and s-cepheids. The comparison of the P-L relations for the twotypes of variable stars shows good agreement, but between them there isa 'gap' with a dim nature.
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A catalogue of field Type II Cepheids
A catalogue of field Type II Cepheids is presented. The primary listconsists of 152 Cepheids sufficiently far from the galactic plane to bevery probably Type II stars. A second list contains 56 additional starsthat are likely, but less certain, Type II Cepheids, including bothstars estimated to be at large distances from the galactic plane butwith uncertain distances and stars close to the galactic plane believedto be Type II for independent reasons.
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Kinematics of field Type II Cepheid variables
The spectra of 49 field Type II Cepheids have been assembled andcombined with 14 additional stars with previously published radialvelocities in order to investigate the kinematics and spectralcharacteristics of these stars. Many of the stars have low peculiarvelocities consistent with circular rotation around the galaxy, whilesome are high-velocity stars. Outside the nuclear bulge, the velocitiesare correlated with photometric metallicities in the sense thatmetal-rich stars show a nearly normal, disklike rotation velocity and alow velocity dispersion. This correlation shows that the low-velocity,metal-rich stars have an old-disk origin. Fewer Cepheids are found inthe field than expected relative to clusters, suggesting a differencebetween the populations of the halo field and clusters. The kinematicproperties of Cepheids in the nuclear bulge appear to be different inthat both metal-poor and metal-rich Cepheids have a high velocitydispersion and show little systematic galactic rotation.
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Period changes of Cepheid variables. I - Secular period changes
Secular period changes of one hundred northern Cepheids are investigatedwith the help of O-C diagrams. With the classical Cepheids the rate ofobserved period changes is in good agreement with that determined fromstellar evolution theory. The period noise cannot mask the evolutionaryperiod changes especially in longer period Cepheids for which theoccurrence of parabolic O-C graphs is unusually frequent.
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