Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes
Context: The dependence of amplitude on the pulsation period differsfrom other Cepheid-related relationships. Aims: We attempt torevise the period-amplitude (P-A) relationship of Galactic Cepheidsbased on multi-colour photometric and radial velocity data. Reliable P-Agraphs for Galactic Cepheids constructed for the U, B, V, R_C, andIC photometric bands and pulsational radial velocityvariations facilitate investigations of previously poorly studiedinterrelations between observable amplitudes. The effects of bothbinarity and metallicity on the observed amplitude, and the dichotomybetween short- and long-period Cepheids can both be studied. Methods: A homogeneous data set was created that contains basicphysical and phenomenological properties of 369 Galactic Cepheids.Pulsation periods were revised and amplitudes were determined by theFourier method. P-A graphs were constructed and an upper envelope to thedata points was determined in each graph. Correlations between variousamplitudes and amplitude-related parameters were searched for, usingCepheids without known companions. Results: Large amplitudeCepheids with companions exhibit smaller photometric amplitudes onaverage than solitary ones, as expected, while s-Cepheids pulsate withan arbitrary (although small) amplitude. The ratio of the observedradial velocity to blue photometric amplitudes, AV_RAD/A_B,is not as good an indicator of the pulsation mode as predictedtheoretically. This may be caused by an incorrect mode assignment to anumber of small amplitude Cepheids, which are not necessarily firstovertone pulsators. The dependence of the pulsation amplitudes onwavelength is used to identify duplicity of Cepheids. More than twentystars previously classified as solitary Cepheids are now suspected tohave a companion. The ratio of photometric amplitudes observed invarious bands confirms the existence of a dichotomy among normalamplitude Cepheids. The limiting period separating short- andlong-period Cepheids is 10.47 days. Conclusions:Interdependences of pulsational amplitudes, the period dependence of theamplitude parameters, and the dichotomy have to be taken into account asconstraints in modelling the structure and pulsation of Cepheids.Studies of the P-L relationship must comply with the break at 10.47°instead of the currently used “convenient” value of 10 days.Table 1 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/504/959
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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.
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Reddenings of FGK supergiants and classical Cepheids from spectroscopic data
Accurate and homogeneous atmospheric parameters(Teff,logg,Vt, [Fe/H]) are derived for 74 FGKnon-variable supergiants from high-resolution, high signal-to-noiseratio, echelle spectra. Extremely high precision for the inferredeffective temperatures (10-40K) is achieved by using the line-depthratio method. The new data are combined with atmospheric values for 164classical Cepheids, observed at 675 different pulsation phases, takenfrom our previously published studies. The derived values are correlatedwith unreddened B - V colours compiled from the literature for theinvestigated stars in order to obtain an empirical relationship of theform (B - V)0 = 57.984 -10.3587(logTeff)2 +1.67572(logTeff)3 - 3.356logg +0.0321Vt + 0.2615[Fe/H] + 0.8833(logg)(logTeff).The expression is used to estimate colour excesses E(B - V) forindividual supergiants and classical Cepheids, with a precision of+/-0.05 mag for supergiants and Cepheids with n = 1-2 spectra, reaching+/-0.025mag for Cepheids with n > 2 spectra, matching uncertaintiesfor the most sophisticated photometric techniques. The reddening scaleis also a close match to the system of space reddenings for Cepheids.The application range is for spectral types F0-K0 and luminosity classesI and II.
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Photoelectric observations of Cepheids in UBV(RI)c (Berdnikov, 2008)
This catalog gathers the observation of 894 Cepheids made between 1986to 2004.Observations are listed in alphabetical order of the constellations. Thestandard deviation for every magnitude and color is 0.01mag.This version supersedes the 1997 edition (Cat. )(3 data files).
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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Simulating observable comets. III. Real stellar perturbers of the Oort cloud and their output
Context: .This is the third of a series of papers on simulating themechanisms acting currently on the Oort cloud and producing the observedlong-period comets.Aims.In this paper we investigate the influence ofcurrent stellar perturbers on the Oort cloud of comets under thesimultaneous galactic disk tide. We also analyse the past motion of theobserved long-period comets under the same dynamical model to verify thewidely used definition of dynamically new comets. Methods.The action ofnearby stars and the galactic disk tide on the Oort cloud was simulated.The original orbital elements of all 386 long-period comets of qualityclasses 1 and 2 were calculated, and their motion was followednumerically for one orbital revolution into the past, down to theprevious perihelion. We also simulated the output of the close futurepass of GJ 710 through the Oort cloud. Results.The simulated flux of theobservable comets resulting from the current stellar and galacticperturbations, as well as the distribution of perihelion direction, wasobtained. The same data are presented for the future passage of GJ 710.A detailed description is given of the past evolution of aphelion andperihelion distances of the observed long-period comets. Conclusions. Weobtained no fingerprints of the stellar perturbations in the simulatedflux and its directional structure. The mechanisms producing observablecomets are highly dominated by galactic disk tide because all currentstellar perturbers are too weak. Also the effect of the close passage ofthe star GJ 710 is very difficult to recognise on the background of theGalactic-driven observable comets. For the observed comets we found only45 to be really dynamically "new" according to our definition based onthe previous perihelion distance value.
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Galactic Cepheids. I. Elemental Abundances and Their Implementation for Stellar and Galactic Evolution
We have added data for 16 distant Cepheids observed with the echellespectrograph of the Apache Point 3.5 m telescope to improve thecorrelations of abundance parameters with pulsation period and distancefrom the Galactic center (RG ). While we see no importanttrends with pulsation period, some important ratios are closely relatedto the evolution of stars through the instability strip. The mostinteresting is the N/C ratio, which is predicted to be enhanced by afactor of 4 when an evolving supergiant cools to Teff=4000 Kand the outer convection zone reaches the depth at which CN processinghas converted C to N. We find a Gaussian distribution around a value of[N/C]=0.6, just as predicted. The ratio of about 30:1 mixed to unmixedstars can be taken as the ratio of evolutionary time spent on the blueloop to the time spent on the first crossing through the instabilitystrip. According to stellar models, the main mixing event takes placewhen Teff drops below 4000 K, which is outside the red edgeof the instability strip; i.e., after stars have crossed the instabilitystrip for the first time. We have confirmed previously knowncorrelations of [Fe/H] with RG. We find that [Fe/H] shows agradient of -0.06 Kpc-1. The only other significant gradientis that of [Eu/Fe], which increases with RG, thereby showingan increasing ratio of SN II/SN Ia in the outer Galaxy.
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New Period-Luminosity and Period-Color relations of classical Cepheids: I. Cepheids in the Galaxy
321 Galactic fundamental-mode Cepheids with good B, V, and (in mostcases) I photometry by Berdnikov et al. (\cite{Berdnikov:etal:00}) andwith homogenized color excesses E(B-V) based on Fernie et al.(\cite{Fernie:etal:95}) are used to determine their period-color (P-C)relation in the range 0.4~ 1.4). The latter effect is enhanced by asuggestive break of the P-L relation of LMC and SMC at log P = 1.0towards still shallower values as shown in a forthcoming paper.Table 1 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/404/423
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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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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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New spectroscopic binaries among classical Cepheids. II.
Radial velocity measurements of classical Cepheids obtained by theCORAVEL and ELODIE spectrographs have been analysed. The comparison withearlier radial velocity data resulted in the discovery of eight newspectroscopic binaries (in the 9.7'-12.4' interval of meanV-brightness). An updated value of the pulsation period is alsodetermined for the new SB-Cepheids.
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The shape and scale of Galactic rotation from Cepheid kinematics
A catalog of Cepheid variables is used to probe the kinematics of theGalactic disk. Radial velocities are measured for eight distant Cepheidstoward l = 300 deg; these new Cepheids provide a particularly goodconstraint on the distance to the Galactic center, R0. We model the diskwith both an axisymmetric rotation curve and one with a weak ellipticalcomponent, and find evidence for an ellipticity of 0.043 +/- 0.016 nearthe sun. Using these models, we derive R0 = 7.66 +/- 0.32 kpc andv(circ) = 237 +/- 12 km/s. The distance to the Galactic center agreeswell with recent determinations from the distribution of RR Lyraevariables and disfavors most models with large ellipticities at thesolar orbit.
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Galactic kinematics of Cepheids from HIPPARCOS proper motions
The Hipparcos proper motions of 220 Galactic Cepheids, together withrelevant ground-based photometry, have been analyzed. The effects ofGalactic rotation are very clearly seen. Mean values of the Oortconstants, A = 14.82 +/- 0.84 km/s kpc, and B = -12.37 +/- 0.64 km/skpc, and of the angular velocity of circular rotation at the sun, 27.19+/- 0.87 km/s kpc, are derived. A comparison of the value of A withvalues derived from recent radial velocity solutions confirms, withinthe errors, the zero-points of the period-luminosity andperiod-luminosity-color relations derived directly from the Hipparcostrigonometrical parallaxes of the same stars. The proper motion resultssuggest that the Galactic rotation curve is declining slowly at thesolar distance from the Galactic Center (-2.4 +/- 1.2 km/s kpc). Thecomponent of the solar motion towards the North Galactic Pole is foundto be +7.61 +/- 0.64 km/s. Based on the increased distance scale deducedin the present paper, the distance to the Galactic Center derived in aprevious radial velocity study is increased to 8.5 +/- 0.5 kpc.
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Rotation of the outer disc from classical cepheids.
Radial velocities and distances have been measured for a sample of 48remote classical cepheids located in the outer disc of the Galaxy(118deg
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The Behlen Observatory Variable Star Survey.IV.
Finding charts, accurate coordinates, and light curves are presented for106 variable stars including 6 which are newly discovered. Parametersdescriptive of the light curves are tabulated including periods for 16stars which lacked them. The periods from the General Catalog ofVariable Stars for ten stars were found to be seriously in error. Theclassification of the stars is discussed. Revisions or refinements ofthe classifications from the General Catalogue of Variable Stars aresuggested for 20 stars and classifications are given for 7 which werepreviously unclassified. 15%-23% of the Bailey type ab RR Lyrae starsshow scatter in their light curves which is suggestive of the Blazhkoeffect.
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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
Not Available
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New radial velocities for classical cepheids. Local galactic rotation revisited
New centre-of-mass radial velocities are calculated for 107 classicalcepheids from CORAVEL observations. We generally determine thesevelocities from four to six measurements carefully spaced in phase, byfitting a "typical" radial velocity curve or the mirror image of thelight curve. A decomposition in Fourier series is used for stars withmore than 10 measurements. Distances are then computed through aperiod-luminosity-colour relation for 278 classical cepheids with knownradial velocity, and an axisymmetric galactic rotation model is appliedto the sample, using a generalised non-linear least square method withuncertainties on both the velocities and the distances. The bestresults, with a rotation curve modelled as a third order polynomial,are: Rsun_=8.09 +/-0.30 kpc, A=15.92 +/-0.34 km/s/kpc, 2ARsun_=257 +/-7 km/s, A2=d^2theta(R)/d R^2^=-3.38+/-0.38 km/s/kpc^2^, A3=d^3theta(R)/d R^3^=1.99 +/-0.62km/s/kpc^3^, u_0_=9.32 +/-0.80 km/s, v_0_=11.18 +/-0.65 km/s. The effectof modifying the distance scale of cepheids, the absorption coefficientor the fitting procedure algorithm are examined. It appears that theproduct 2 A Rsun_ is very robust towards these changes. Theextended sample of classical cepheids with known radial velocitypresented in this paper seems to imply a higher value for A thananterior studies. The radial velocity residuals show a systematic k-termof about 2 km/s. New evidence from cluster cepheids excludes anintrinsic cause for this shift, and a dynamical cause is proposed from acomparison with a N-body simulation of the Galaxy. The simulation showsthat a systematic bias of this magnitude is typical. The structure ofthe local residual velocity field is examined in some detail.
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The separation of S-Cepheids from classical Cepheids and a new definition of the class
Fourier decomposition has been applied to a sample of 184 classical andS-Cepheids with P less than 8 d and a careful evaluation of errors inthe determination of the parameters has been made. The S-Cepheids starsare redefined by the authors as Population I Cepheids that do not followthe Hertzsprung progression, but have a progression of their own. In thephi(21)-P plane, the S- and classical Cepheids are characterized by twosequences well separated for P less than 5.5 d. In the period range Pbetween 3d and 5.5 d, two different progressions are also present in thephi(31)-P plane while a discriminating value R(21) = 0.20 can be seen inthe R(21)-P plane. The first overtone pulsation seems to be wellestablished for S-Cepheids with P less then 3.2 d; it is probable forall the stars of the redefined subclass. A discontinuity is clearlyvisible at about 3 d in the S-Cepheid sequence in the phi(21)-P plane;it is interpreted as a resonance effect. An apparent decrease in thenumber of stars is present in the classical sequence for P less than 3d.
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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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Classical Cepheids - Their distances and space distribution
A simplified method of calculating classical Cepheid distances isproposed. It is based on photometric data, without the use of thereddenings. By means of results obtained in this way the followingproblems are discussed: Cepheid double and more numerous aggregates andproperties of the cluster and association Cepheid.
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Milky Way rotation and the distance to the galactic center from Cepheid variables
The compiled photometry, reddenings, and radial velocities of GalacticCepheids are fit with an axisymmetric Galactic rotation model. R(0) =7.8 + or - 0.7 kpc and 2AR(0) = 228 + or - 19 km/s are derived. The LMCdistance modulus is 18.45 on the same absolute calibration. ObservedCepheid gamma velocities appear on average to be 30 + or - 1 km/s morenegative than the true corresponding center-of-mass velocities. Thetrend of increasing blueness toward larger Galactocentric radiusconfirms the radial metallicity gradient found spectroscopically.
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The catalogue of light curves parameters, distances and space coordinates of classical Cepheids.
Not Available
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Classification of intrinsic variables. IX - The Cepheid domain
The present H-beta, RI and intermediate band observations obtained for135 high mass, long- and short-period Cepheids (LPC and SPC) throughoutthe cycle of variation are combined with observations for 100 ultrashortperiod Cepheids in order to delineate the Cepheid domain in the (beta,/C1/) and (M-bol, log Te) planes. The independently derived luminositycalibrations for bright giants and supergiants previously published arefound to closely reproduce the luminosities derived from theSandage-Tammann (1968) PL relation for most variables. The majority ofthe LPC appear to be overabundant in metals by comparison to the sun,and reddening determinations for the LPC suggest a small systematiccorrection to previous results.
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The Catalogue of Distances and Light Absorption for Cepheids
Not Available
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Photometric abundances of classical Cepheids and the gradient in the galactic disk
Washington-system colors and V magnitudes are described for 102classical Cepheids with a wide range of positions in the disk of thegalaxy. A period-color relation is derived and, with a period-luminosityrelation, is used to determine reddenings and distances. The colors areinterpreted in terms of abundances, with a calibration based on observedstars with known abundances and on model-atmosphere colors. The Cepheidsshow (1) a gradient in the disk of the derivative with respect to r ofthe derived metal abundance, logarithmic relative to the sun =-0.07/kpc, approximately linear over 10 kpc; (2) a small scatter in theabundances of most stars at a given galactic position; and (3) a fewstars with colors indicating peculiar abundances. The possible effectsof companion stars, helium abundance variations, and peculiar reddeningare discussed and are shown to be unimportant. The implications forgalactic evolution are discussed.
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Supergiant and Variable Stars in Chi-Persei and H-Persei Cluster Region
Not Available
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The structure of the Cepheid instability strip
The properties of Cepheids in the Galaxy, LMC, and SMC are analyzed tocompare them with theoretical models. The PLC relationships of the LMCand SMC agree with theoretically derived PLC relationships when fittingof data is done by the maximum likelihood method. Differences in the tworelationships can be ascribed to abundance differences. Empirical blueedges in the period-color plane agree with models for log P not greaterthan 1.1, but have significantly steeper slopes at longer periods; theredoes not seem to be any satisfactory explanation of this.
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