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The Distribution of the Elements in the Galactic Disk. III. A Reconsideration of Cepheids from l = 30° to 250°
This paper reports on the spectroscopic investigation of 238 Cepheids inthe northern sky. Of these stars, about 150 are new to the study of thegalactic abundance gradient. These new Cepheids bring the total numberof Cepheids involved in abundance distribution studies to over 400. Inthis work, we also consider systematics between various studies and alsothose which result from the choice of models. We find that systematicvariations exist at the 0.06 dex level both between studies and modelatmospheres. In order to control the systematic effects our finalgradients depend only on abundances derived herein. A simple linear fitto the Cepheid data from 398 stars yields a gradient d[Fe/H]/dRG = -0.062 ± 0.002 dex kpc-1which is in good agreement with previously determined values. We havealso re-examined the region of the "metallicity island" of Luck et al.With the doubling of the sample in that region and our internallyconsistent abundances, we find that there is scant evidence for adistinct island. We also find in our sample the first reported Cepheid(V1033 Cyg) with a pronounced Li feature. The Li abundance is consistentwith the star being on its redward pass toward the first giant branch.
| A High-resolution, Multi-epoch Spectral Atlas of Peculiar Stars Including RAVE, GAIA , and HERMES Wavelength Ranges
We present an Echelle+CCD, high signal-to-noise ratio, high-resolution(R = 20,000) spectroscopic atlas of 108 well-known objectsrepresentative of the most common types of peculiar and variable stars.The wavelength interval extends from 4600 to 9400 Å and includesthe RAVE, Gaia, and HERMES wavelength ranges. Multi-epoch spectra areprovided for the majority of the observed stars. A total of 425 spectraof peculiar stars, which were collected during 56 observing nightsbetween 1998 November and 2002 August, are presented. The spectra aregiven in FITS format and heliocentric wavelengths, with accuratesubtraction of both the sky background and the scattered light.Auxiliary material useful for custom applications (telluric dividers,spectrophotometric stars, flat-field tracings) is also provided. Theatlas aims to provide a homogeneous database of the spectral appearanceof stellar peculiarities, a tool useful both for classification purposesand inter-comparison studies. It could also serve in the planning anddevelopment of automated classification algorithms designed for RAVE,Gaia, HERMES, and other large-scale spectral surveys. The spectrum of XXOph is discussed in some detail as an example of the content of thepresent atlas.
| KP Cyg: An Unusual Metal-Rich RR Lyr Type Star of Long Period
We present the results of a detailedspectroscopic study of the long-period (P=0.856 days) RR Lyrae star, KPCyg. We derived abundances of many chemical elements including the lightspecies, iron-group elements and elements of the s-processes. Most RRLyrae stars with periods longer than 0.7 days are metal-deficientobjects. Surprisingly, our results show that KP Cyg is very metal rich([Fe/H]=+0.18±0.23). By comparison with a number of short-period(P=1˜6 days), metal-rich CWB stars, we suggest that KP Cyg may bea very short-period CWB star (BL Her star) rather than an RR Lyrae star.As seen in some CWB stars, KP Cyg shows strong excesses of carbon andnitrogen in its atmosphere. This indicates that the surface of KP Cyghas been polluted by material that has undergone helium burning (toenhance carbon) and proton capture (to transform carbon into nitrogen).We also note that UY CrB, whose period is 0.929 days, also shows anenhancement of C and N, and that two carbon Cepheids of short period,V553 Cen and RT TrA, show similar excesses of carbon and nitrogen.
| Pulsation and orbit of AU Pegasi
AU Pegasi is a pulsating star in a spectroscopic binary system with anorbital period of 53.26 days. Between 1960 and 1990 an extremely rapidperiod increase was observed in the value of the pulsation period, butin the last 15 years the observation show that the period set in 2.411days. Fourier analysis of photometric data obtained during the ASASproject and those taken at the Piszkésteto Mountain Station ofthe Konkoly Observatory during 1994-2005 indicate that AU Pegasi ispulsating in two modes simultaneously, and the ratio of the frequenciesof the two modes is 0.706, a value common for double-mode classicalCepheids. A careful analysis of other photometric observations obtainedduring the era of the strong period increase also revealed existence ofa second mode. This may suggest that this star is not a Type II Cepheid,despite its galactic position.
| The Chemical Compositions of the Type II Cepheids-The BL Herculis and W Virginis Variables
Abundance analyses from high-resolution optical spectra are presentedfor 19 type II Cepheids in the Galactic field. The sample includes bothshort-period (BL Her) and long-period (W Vir) stars. This is the firstextensive abundance analysis of these variables. The C, N, and Oabundances with similar spreads for the BL Her and W Vir show evidencefor an atmosphere contaminated with 3α process and CN-cyclingproducts. A notable anomaly of the BL Her stars is an overabundance ofNa by a factor of about 5 relative to their presumed initial abundances.This overabundance is not seen in the W Vir stars. The abundanceanomalies running from mild to extreme in W Vir stars but not seen inthe BL Her stars are attributed to dust-gas separation that provides anatmosphere deficient in elements of high condensation temperature,notably, Al, Ca, Sc, Ti, and s-process elements. Such anomalies havepreviously been seen among RV Tau stars which represent a long-periodextension of the variability enjoyed by the type II Cepheids. Commentsare offered on how the contrasting abundance anomalies of BL Her and WVir stars may be explained in terms of the stars' evolution from theblue horizontal branch.
| TYC 1031 01262 1: the first known Galactic eclipsing binary with a Type II Cepheid component
We present the discovery and CCD observations of the first eclipsingbinary with a Type II Cepheid component in our Galaxy. The pulsation andorbital periods are found to be 4.1523 and 51.38 d, respectively, i.e.this variable is the system with the shortest orbital period among knownCepheid binaries. Pulsations dominate the brightness variations. Theeclipses are assumed to be partial. The EB-subtype eclipsing light curveleads us to believe that the binary components are non-spherical.
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Cepheidenbeobachtung in der BAV: Ruckblick und Ausblick.
Not Available
| The Spectra of Type II Cepheids. I. The Hα Line in Short-Period Stars
We present 88 Hα profiles for 24 pulsating variable stars withperiods between 1 and 3 days in order to explore the behavior of thisline in type II as compared with classical Cepheids. Surprisingly, largevelocity differences were found between Hα and the metal lines insome type II Cepheids. Strong emission was observed in three stars, VZAql, NW Lyr, and V439 Oph, while line filling by incipient emission ispresent in seven others. All of the stars with emission and most withincipient emission belong to Diethelm's AHB2 class, and the emission isassociated with the secondary bump on the rising branch of the lightcurve. Two stars, BF Ser and MQ Aql, show doubling of the core nearmaximum light, and asymmetry of the line is noted in some spectra.Based in part on observations obtained with the Apache Point Observatory3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
| The Cepheids of Population II and Related Stars
The Type II Cepheids include most intrinsic variables with periodsbetween 1 and about 50 days, except for the classical Cepheids and theshortest semiregular variables of type M. The Type II Cepheids may bedivided in groups by period, such that the stars with periods beween 1and 5 days (BL Her class), 10-20 days (W Vir class), and greater than 20days (RV Tau class) have differing evolutionary histories. The chemicalcomposition of Type II Cepheids reflects the material they were madefrom as modified by their internal nuclear evolution and mixing.Finally, RV Tau stars are affected by mass loss by dust and speciesattached to the dust. The populations to which the various classes ofType II Cepheids are assigned constitute important clues to the originand evolution of the halo of our Galaxy and the dwarf spheroidal systemsfrom which at least part of the halo seems to have been accreted.
| The MACHO Project Large Magellanic Cloud Variable Star Inventory. XII. Three Cepheid Variables in Eclipsing Binaries
We present a method for solving the light curve of an eclipsing binarysystem that contains a Cepheid variable as one of its components as wellas the solutions for three eclipsing Cepheids in the Large MagellanicCloud (LMC). A geometric model is constructed in which the componentstars are assumed to be spherical and on circular orbits. The emergentsystem flux is computed as a function of time, with the intrinsicvariations in temperature and radius of the Cepheid treatedself-consistently. Fitting the adopted model to photometricobservations, incorporating data from multiple bandpasses, yields asingle parameter set best describing the system. This method is appliedto three eclipsing Cepheid systems from the MACHO project LMC database:MACHO 6.6454.5, 78.6338.24, and 81.8997.87. A best-fit value is obtainedfor each system's orbital period and inclination and for the relativeradius, color, and limb-darkening coefficients of each star. Pulsationperiods and parameterizations of the intrinsic color variations of theCepheids are also obtained, and the amplitude of the radial pulsation ofeach Cepheid is measured directly. The system 6.6454.5 is found tocontain a 4.97 day Cepheid, which cannot be definitely classified astype I or type II, with an unexpectedly brighter companion. The system78.6338.24 consists of a 17.7 day, W Virginis class type II Cepheid witha smaller, dimmer companion. The system 81.8997.87 contains anintermediate-mass, 2.03 day overtone Cepheid with a dimmer, red giantsecondary.
| Cepheiden: was wird beobachtet - was nicht ?
Not Available
| 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.
| Fourier Analysis of Hipparcos Photometry of Cepheid Variables
Fourier parameters have been computed for 240 field Cepheids observed bythe Hipparcos satellite. We have identified three new PopulationIovertone Cepheids: V411Lac, V898 Cen and V572 Aql. We have comparedFourier progressions of Population I and Population II Cepheids. Thepossibility of using Fourier parameters to distinguish between the twotypes is discussed.
| 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
| Period Changes in Population II Cepheids: TX Del and W Vir
We have used the Hipparcos database of epoch photometry to study thevariability of two Population II Cepheids: TX Del and W Vir. We haveconstructed (O-c) diagrams for these stars, using the new data and datafrom the literature. The period of TX Del is decreasing, at a ratewhich is consistent with evolutionary predictions. THe periodchange ofW Vir is uncertain because of the many recent gaps in the data of thisstar. We urge AAVSO visual and photoelectric observers to monitorPopulation II Cepheids more systematically, since amny of these starshave unstable periods, and at least one has an unstable amplitude.
| 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.
| 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.
| 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.
| 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.
| 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
| ST Pup: a binary Type II Cepheid with a peculiar chemical composition
Analysis of recent photometric observations of the W Vir star ST Pupreveals that it has experienced one sudden period change in the last 35years. This is in sharp contrast to its erratic behaviour in the firsthalf of this century when the period changed much more frequently.Application of the surface brightness version of the Baade-Wesselinkmethod to the observations yields M_v=-3.86+/-0.2. Using spectroscopicobservations spanning almost 7yr, we have discovered that ST Pup is asingle-lined spectroscopic binary. The orbital period, 410.4+/-2.9d, isconsiderably longer than that of the other three known binary Type IICepheids, which average about 100d. It has a very low orbitaleccentricity, implying that orbital circularization and mass transferhave already taken place in this system. We estimate that[Fe/H]=-1.47+/-0.13 from a local thermodynamic equilibrium (LTE) fineanalysis of high-resolution spectra obtained near minimum light. Thevalue of C/O is 0.3, demonstrating that ST Pup is not a carbon star eventhough it displays strong CH and CN bands near minimum light. Most ofthe elements show an abundance pattern that correlates with condensationtemperature similar to that of diffuse interstellar clouds and peculiarhigh-latitude A-F supergiants, which have been interpreted as low-masspost-AGB stars that have undergone selective mass-loss via grainformation. However, the Ca/Ti abundance ratio in the atmosphere of STPup is too high to be consistent with this interpretation. The Caanomaly may have been caused by overionization of Ca^+ by Lyalphaphotons when the star was losing mass. An infrared excess is seen at theJHKL and IRAS bands, indicating the presence of dust spanning a largerange in distance from ST Pup.
| A spectroscopic study of the pulsating star BL Her
Not Available
| 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
| 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.
| A new approach to the surface brightness method for cepheid radii determination.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994RMxAA..29..148R&db_key=AST
| Study of the population II Cepheid AU Pegasi
New photoelectric B and V observations of the Population II Cepheid AUPeg are presented. The available photometric measurements are collectedfrom the literature and all data are analyzed with severalperiod-finding methods. The period variation has been found to benon-linear, and between 1986 and 1990 the period increase stopped andseems to reverse. Since this Cepheid is a member of a binary systemwhere proximity of the components is a deterministic factor, it isprobable that the pulsation is perturbed by the companion's tidal force.However, such a period variation can hardly be explained by tidalinteraction alone. The surface brightness analysis resulted in newabsolute parameters indicating that AU Peg is on the red edge of theinstability strip.
| 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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Osservazione e dati astrometrici
| Costellazione: | Pegaso |
| Ascensione retta: | 21h24m00.24s |
| Declinazione: | +18°16'43.8" |
| Magnitudine apparente: | 9.23 |
| Moto proprio RA: | -1 |
| Moto proprio Dec: | -13.2 |
| B-T magnitude: | 10.364 |
| V-T magnitude: | 9.324 |
Cataloghi e designazioni:
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