Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Near-infrared (JHK) Photometry of 131 Northern Galactic Classical Cepheids
Near-infrared photometric measurements for 131 Northern GalacticCepheids are presented. The Cepheid light curves are sampled with anaverage of 22 measurements per star fully covering the phase of eachCepheid. The J, H, and K light curves for each Cepheid were uniformlyinterpolated to find the intensity mean magnitudes within each band. Theresults are consistent within ±1% for 26 stars in common withprevious studies. This paper is the first in a projected series of twopapers which will provide additional fundamental data for Cepheids inthe Galaxy, namely, NIR photometry and line-of-sight extinction. In thecourse of this project, 93 additional variables were fortuitouslyobserved within the Cepheid program fields, 82 of which have previouslynot been identified.
| 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
| 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).
| 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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| Two Period-Radius Relations for Classical Cepheids: Determining the Pulsation Mode and the Distance Scale
Not Available
| 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.
| 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
| Multi-colour PL-relations of Cepheids in the bt HIPPARCOS catalogue and the distance to the LMC
We analyse a sample of 236 Cepheids from the hipparcos catalog, usingthe method of ``reduced parallaxes'' in V, I, K and the reddening-free``Wesenheit-index''. We compare our sample to those considered by Feast& Catchpole (1997) and Lanoix et al. (1999), and argue that oursample is the most carefully selected one with respect to completeness,the flagging of overtone pulsators, and the removal of Cepheids that mayinfluence the analyses for various reasons (double-mode Cepheids,unreliable hipparcos solutions, possible contaminated photometry due tobinary companions). From numerical simulations, and confirmed by theobserved parallax distribution, we derive a (vertical) scale height ofCepheids of 70 pc, as expected for a population of 3-10 Msunstars. This has consequences for Malmquist- and Lutz-Kelker (Lutz &Kelker 1973, Oudmaijer et al. 1998) type corrections which are smallerfor a disk population than for a spherical population. The V and I datasuggest that the slope of the Galactic PL-relations may be shallowerthan that observed for LMC Cepheids, either for the whole period range,or that there is a break at short periods (near log P_0 ~ 0.7-0.8). Westress the importance of two systematic effects which influence thedistance to the LMC: the slopes of the Galactic PL-relations andmetallicity corrections. In order to assess the influence of thesevarious effects, we present 27 distance moduli (DM) to the LMC. Theseare based on three different colours (V,I,K), three different slopes(the slope observed for Cepheids in the LMC, a shallower slope predictedfrom one set of theoretical models, and a steeper slope as derived forGalactic Cepheids from the surface-brightness technique), and threedifferent metallicity corrections (no correction as predicted by one setof theoretical models, one implying larger DM as predicted by anotherset of theoretical models, and one implying shorter DM based onempirical evidence). We derive DM between 18.45 +/- 0.18 and 18.86 +/-0.12. The DM based on K are shorter than those based on V and I andrange from 18.45 +/- 0.18 to 18.62 +/- 0.19, but the DM in K could besystematically too low by about 0.1 magnitude because of a bias due tothe fact that NIR photometry is available only for a limited number ofstars. From the Wesenheit-index we derive a DM of 18.60 +/- 0.11,assuming the observed slope of LMC Cepheids and no metallicitycorrection, for want of more information. The DM to the LMC based on theparallax data can be summarised as follows. Based on the PL-relation inV and I, and the Wesenheit-index, the DM is 18.60 ± 0.11(± 0.08 slope)(^{+0.08}_{-0.15} ;metallicity), which is ourcurrent best estimate. Based on the PL-relation in K the DM is ;;;;18.52 +/- 0.18 (± 0.03 ;slope) (± 0.06 ;metallicity)(^{+0.10}_{-0} ;sampling ;bias). The random error is mostly due to thegiven accuracy of the hipparcos parallaxes and the number of Cepheids inthe respective samples. The terms between parentheses indicate thepossible systematic uncertainties due to the slope of the GalacticPL-relations, the metallicity corrections, and in the K-band, due to thelimited number of stars. Recent work by Sandage et al. (1999) indicatesthat the effect of metallicity towards shorter distances may be smallerin V and I than indicated here. From this, we point out the importanceof obtaining NIR photometry for more (closeby) Cepheids, as for themoment NIR photometry is only available for 27% of the total sample.This would eliminate the possible bias due to the limited number ofstars, and would reduce the random error estimate from 0.18 to about0.10 mag. Furthermore, the sensitivity of the DM to reddening,metallicity correction and slope are smallest in the K-band. Based ondata from the ESA HP astrometry satellite.
| 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.
| 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.
| Structural properties of s-Cepheid velocity curves Constraining the location of the omega_4 = 2omega_1 resonance
The light curves of the first overtone Pop. I Cepheids (s-Cepheids) showa discontinuity in their phi_ {21} vs. {P} diagram, near {P} = 3.2 day.This feature, commonly attributed to the 2:1 resonance between the firstand the fourth overtones (omega_4 ~ 2omega_1 ), is not reproduced by thehydrodynamical models. With the goal of reexamining the resonancehypothesis, we have obtained new CORAVEL radial velocity curves for 14overtone Cepheids. Together with 10 objects of Krzyt et al.( te{krzyt}), the combined sample covers the whole range of overtoneCepheid periods. The velocity Fourier parameters display a strongcharacteristic resonant behavior. In striking contrast to photometricones, they vary smoothly with the pulsation period and show no jump at3.2 day. The existing radiative hydrodynamical models match the velocityparameters very well. The center of the omega_4 = 2omega_1 resonance isestimated to occur at {P}r = 4.58\pm 0.04 day, i.e. at aperiod considerably longer than previously assumed (3.2 day). Weidentify two new members of the s-Cepheid group: MYPup and V440 Per. Based on observationscollected at the European Southern Observatory (La Silla, Chile) and atthe Observatoire de Haute-Provence (France)}
| A catalog of Cepheid radial velocities measured in 1995-1998 with the correlation spectrometer
We present a catalog of 2444 original radial-velocity measurements for108 Cepheids based on the 1995-1998 observations with the correlationspectrometer. Detailed radial-velocity curves are given for 12 Cepheidsfor the first time.
| The radii of 62 classical Cepheids
Based on dense series of photoelectric observations and on ourradial-velocity measurements, we calculated the radii of 62 northernCepheids by Balona's method. We derived the following period-radiusrelation: log R = 1.23(+/-0.03) + 0.62(+/-0.03) log P. Our detailedanalysis shows that the distance scale for Cepheids cannot be refinedusing their radii by an independent method which is unrelated to thedistances to young open clusters because of the random and systematicerrors of the Baade-Wesselink technique.
| 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.
| A catalog of Cepheid radial velocities measured in 1992-1995 with a correlation spectrometer
Not Available
| Mean radial velocities and binarity of cepheids from the 1987-1995 measurements
Not Available
| The Fourier decomposition of new light curves of Cepheids with P<7 D
In this paper the Fourier decomposition was applied to photoelectric andCCD measurements of faint Cepheids for which the light curve wassupplied for the first time with a sufficient accuracy. The Fourierdecomposition is confirmed to be a pulsation mode discriminator and thisproperty is discussed by considering also the case of the double-modeCepheid TU Cas. The analysis allowed us to detect three new firstovertone pulsators and to better define the behaviour of the Hertzsprungprogression for classical Cepheids with P<3 d. Some uncertainties areleft only for Cepheids located exactly on the discontinuity at P =~3 dand for Cepheids with an apparently perfect sinusoidal light curve. Atthe present time, the Fourier decomposition cannot be used todiscriminate safely between Pop. I and Pop. II stars. However, morenumerous and precise measurements should allow us to clarify also theseopen questions.
| The SVS Numbering Series Discontinued
Not Available
| Gamma velocities of 58 faint Milky Way Cepheids
Using new radial velocity measurements of 47 faint southern hemisphereGalactic Cepheids, together with additional velocity data from Metzgeret al. (1991), gamma velocities are found for 58 low galactic latitudeCepheids. The gamma velocity is determined by using the period of aCepheid to generate a 'typical' velocity curve, then fitting the curveto the velocity measurements using two free parameters, the gammavelocity, and the phase. The velocity curve is generated using a secondorder Fourier series with coefficients determined from the period. Forthe Cepheids with observations that sample the velocity curve over avariety of pulsation phases, gamma velocities are determined to betterthan 1.0 km/s. Good agreement between these gamma velocities andpreviously published values where they exist.
| Radial velocities of 26 northern Milky Way Cepheids
Spectra taken with the Palomar 60 inch echelle spectrograph are used toobtain 231 radial velocity measurements of 26 northern hemisphere MilkyWay Cepheids with latitude between 15 and 140 deg and b below 5 deg. Thetypical accuracy of the Cepheid velocities is 0.8 km/s. Radialvelocities of standard stars with accuracies of 0.6 km/s are alsoreported, and zero points determined from several systems are compared.The adopted zero point agrees with those of several other systems to +or - 0.1 km/s.
| The Catalogue of Distances and Light Absorption for Cepheids
Not Available
| Le type de population des céphéides galactiques; critères de distinction des types et catalogue
Not Available
| A search for Cepheids in galactic clusters.
Abstract image available at:http://adsabs.harvard.edu/abs/1957ApJ...126..323V
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Cigno |
| Ascensione retta: | 20h15m58.33s |
| Declinazione: | +35°00'53.0" |
| Magnitudine apparente: | 10.762 |
| Moto proprio RA: | -1.6 |
| Moto proprio Dec: | -4 |
| B-T magnitude: | 12.377 |
| V-T magnitude: | 10.896 |
Cataloghi e designazioni:
|
