Contents
Images
Upload your image
DSS Images Other Images
Related articles
Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Proper identification of RR Lyrae stars brighter than 12.5 mag
RR Lyrae stars are of great importance for investigations of Galacticstructure. However, a complete compendium of all RR-Lyraes in the solarneighbourhood with accurate classifications and coordinates does notexist to this day. Here we present a catalogue of 561 local RR-Lyraestars (V_max ≤ 12.5 mag) according to the magnitudes given in theCombined General Catalogue of Variable Stars (GCVS) and 16 fainter ones.The Tycho2 catalogue contains ≃100 RR Lyr stars. However, manyobjects have inaccurate coordinates in the GCVS, the primary source ofvariable star information, so that a reliable cross-identification isdifficult. We identified RR Lyrae from both catalogues based on anintensive literature search. In dubious cases we carried out photometryof fields to identify the variable. Mennessier & Colome (2002,A&A, 390, 173) have published a paper with Tyc2-GCVSidentifications, but we found that many of their identifications arewrong.
| The Monoperiodic δ Scuti Star UY Camelopardalis: An Analog to SX Phoenicis and RR Lyrae Variables
We present the results of a 4 year photometric study of thehigh-amplitude δ Scuti (HADS) star UY Camelopardalis. Analysis ofthe available data from 1985 to 2003 shows that UY Cam is monoperiodic.Fourier solutions for individual data sets do not reveal period changesin the star. Although forced parabolic fits to the O-C residualsindicate a measurable period change, the distribution of the data pointsin the O-C diagram and the deviations between fits and observationssuggest that the existence of the period change still has not beenestablished. We demonstrate the presence of amplitude variations fromcycle to cycle and on longer timescales. The pulsation amplitude seemedto change from 1985 to the 2000s, but it remained constant in 2000-2003.UY Cam is located in the upper portion of the δ Scuti instabilityregion. Its photometric properties and estimated physical parametersreveal that UY Cam is an interesting object in terms of its poormetallicity, long period, high luminosity, low surface gravity, andlarge radius among the HADS stars. UY Cam could be a younger (0.7+/-0.1Gyr) Population I HADS star with low metal abundance (Z=0.004) evolvingon its post-main-sequence shell hydrogen burning evolutionary phase. UYCam intervenes among the Population I/II HADS and type c RR Lyraevariables. These characteristics suggest the star to be an analog ofHADS, SX Phoenicis, and RRc variables.
| Asteroseismology of HADS stars: V974 Oph, a radial pulsator flavoured by nonradial components
The analysis of a dense time-series on V974 Oph disclosed the richpulsational content (at least five independent terms) of thishigh-amplitude (0.60 mag in B-light) delta Scts star. A mode with afrequency very close to the main one (probably the fundamental radialmode) has been detected: such a doublet is not a common feature in starsof the same class. Also another term can be considered a radial one, butthe high ratio (0.786) raises some problems that can be solved only byadmitting very low metallicity. It is quite evident that someundetectable terms are again hidden in the noise, as the least-squaresfit leaves a rms residual much higher than the observational noise. Allthat considered, nonradial modes seem to play a key rôle in thelight variability of V974 Oph. Revealing an unsuspected asteroseismicinterest, V974 Oph provides a link between low- and high-amplitude deltaScts stars.Based on observations collected at Europan Southern Observatory, LaSilla, Chile
| delta Sct-type nature of the variable V2109 Cyg
We present the results of simultaneous uvbybeta photometry carried outfrom 1999 to 2001 of the variable V2109 Cyg together with aspectroscopic analysis based on one high resolution spectrum obtained in2000. From this study, the star is definitively classified as an evolveddelta Sct-type variable with solar metal abundances. This conclusion isalso supported by the detected multiperiodic pulsational behaviour andthe observed variation of the m1 index over the pulsationcycle. This variation is slightly reversed relative to the V lightcurve, in very good agreement with the m1 variation expectedfrom the photometric calibrations. Besides the main frequencyf1=5.3745 cd-1 and its first harmonic2f1, a secondary peak is found at f2=5.8332cd-1 (f1/f2=0.92) with f1identified as a radial mode and f2 as non-radial. Whereas nosignificant variations are found in the amplitude of f1 fromseason to season, the amplitude of f2 changes strongly.Moreover, the main period has remained constant since 1990, within theobservational uncertainties. Additional secondary frequencies may alsobe excited in this variable.Based on observations collected at the Sierra Nevada, San PedroMártir and Haute-Provence observatories.Tables 2, 5 and 7 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi -bin/qcat?J/A+A/407/1059
| A comprehensive study of the delta Scuti star AN Lyncis
We present new time-series CCD photometry on the delta Scuti star ANLyn. Analyses based on all the available data show that the amplitude ofthe main frequency increased from 1994 to 2000 at a rate of 0.006 mmagyr-1. Considering all the existing amplitudes, the amplitudevariations seem sinusoidal since 1980. In both periods of 1980-1983 and1994-2001 with data available the amplitudes increased linearly withtime. The amplitudes in the earlier 1980s were higher and they increasedat a higher rate than those in 1994-2001. Amplitude variations of theother frequencies are also present from season to season. The lightvariation of AN Lyn can be explained currently by amplitude variabilityplus multiperiodic pulsation. However, no conclusion can be drawnregarding change of periods and new oscillation contents. The twoindependent frequencies f1=10.1756 cycle d-1 andf2=18.1310 cycle d-1 are confirmed and aresuggested to be the solution of the light variation of AN Lyn. Themixture of radial and nonradial modes of the two frequencies most likelycharacterize the pulsation of the star.
| Physical Parameter Determination of the δ Scuti Star V1719 Cygni
New uvbyβ photoelectric photometry of the short-period variablestar V1719 Cygni (HD 200925) has been secured. A period analysis ofthese data and those reported in the literature has provided us withstable pulsation frequencies that fit all the available observationscovering a time span of 20 yr. The frequencies determined are 3.7411556,7.4823111, 11.2234667, and 4.6777749 cycles day-1 and ofsmaller amplitude 8.4189900 cycles day-1. It was found thatthis Population I star has logg around 3.1 and an effective temperatureof 6750 K.
| Variable stars in the Tycho photometric observations. I. Detection
We present an original way to detect variable stars in the Tychophotometric observations. A modified Kolmogorov-Smirnov statistical testhas been constructed, based on a model of most of the satellite'sparameters, leading to the dispersion in the measurements. This allowsus to build a treatment taking into account truncated detections andcensored measurements, and to search for variability in the faint partof the catalogue. The selection threshold of variable stars has beencalibrated to minimize false alarm rate. Reliable results were thusobtained for stars as faint as 11 mag. One thousand and ninety-onesuspected variable stars have been listed, 407 of which are alreadyknown in Hipparcos, GCVS or NSV, and 684 of which are suspected variablestars to be identified soon.
| delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The light curves of the short-period variable stars in omega Centauri
The Fourier decomposition was applied to the light curves of the shortperiod variable stars discovered by the OGLE team (Kaluzny et al. 1996,1997) in omega Cen. The progression of the {f_2} u parameter as afunction of the period is extended toward very short periods as the newvalues connected directly to those of stars located in the Galaxy.However, two groups of stars deviate: the first is located around 0.038d and it shows rather high {f_2} u values; the second is the origin of asmall change in the slope around 0.050 d. The reality of the twofeatures is discussed. The peculiarity of the light curve of OGLEGC 26is also emphasized.
| Mode identification and asteroseismology of delta Scuti stars
The use of multicolour photometry for mode identification in pulsatingstars is discussed. We present a new, statistically based, algorithm forfinding the best estimate of the spherical harmonic degree, and aconfidence level from which the uniqueness can be ascertained. Themethod is applied to some well-observed delta Sct stars with multicolourphotometry. We also propose an algorithm to deduce the effectivetemperature, luminosity and equatorial velocity from the observedfrequencies. We find that fixing the modes of at least some frequenciesis essential for a unique solution. The method is applied to a subset ofthe delta Sct stars which have a suitable number of frequencies and modeidentifications.
| The delta Scuti Star GSC 2985-01044
GSC 2985-01044 is a delta Scuti star with a period of 0.0933584 days anda V-magnitude range of 11.85-12.05 its light curve is slightly variable.The location, space motion, and other properties of this star indicatethat it is a higher amplitude delta Scuti star (or ``dwarf Cepheid'')that is a member of the old disk population. The problem of determiningthe local space densities of the various populations of the higheramplitude delta Scuti stars is discussed.
| CCD Photometry of the High-Amplitude delta Scuti Stars V798 Cygni and V831 Tauri
New CCD measurements of the two high-amplitude delta Scuti stars V798Cyg and V831 Tau were carried out. The double-mode pulsation of V798 Cygis demonstrated beyond any doubt. The f_1/f_2 ratio of 0.800 isconfirmed to be related to the unusual shape of the f_1 light curve. Theproperties of the Fourier parameters were revisited also by consideringthe new light curve of V831 Tau. In particular, the classicaldouble-mode pulsators cannot fill the gap in the R_21 distribution. Twonew variable stars were discovered in the field of V798 Cyg.
| Fourier Coefficients of OGLE Variables. III. delta Scuti Stars
Fourier coefficients for delta Scuti from the OGLE dark matter survey ofthe Galactic bulge are compared to the coefficients of similar stars,mainly High Amplitude delta Scuti and SX Phe stars. While in previousstudies there appears to be a division amongst the delta Scuti starsbased upon the R21 parameter, such a division is not apparentin the OGLE stars. There does though appear to be a separation of thedelta Scuti stars based upon the phi31 variable. Thisseparation is not likely due to a metal variation and its cause is notknown. Values for the extinction towards the Galactic bulge can be usedto estimate a distance of approximately 7.6 kpc for the delta Scutistars. One variable does appear to be located beyond the Galactic bulgeat a distance of approximately 21 kpc.
| The absolute magnitudes of RR Lyraes from HIPPARCOS parallaxes and proper motions
We have used HIPPARCOS proper motions and the method of StatisticalParallax to estimate the absolute magnitude of RR Lyrae stars. Inaddition we used the HIPPARCOS parallax of RR Lyrae itself to determineit's absolute magnitude. These two results are in excellent agreementwith each other and give a zero-point for the RR Lyrae M_v,[Fe/H]relation of 0.77+/-0.15 at [Fe/H]=-1.53. This zero-point is in goodagreement with that obtained recently by several groups usingBaade-Wesselink methods which, averaged over the results from thedifferent groups, gives M_v = 0.73+/-0.14 at [Fe/H]=-1.53. Taking theHIPPARCOS based zero-point and a value of 0.18+/-0.03 for the slope ofthe M_v,[Fe/H] relation from the literature we find firstly, thedistance modulus of the LMC is 18.26+/-0.15 and secondly, the mean ageof the Globular Clusters is 17.4+/-3.0 GYrs. These values are comparedwith recent estimates based on other "standard candles" that have alsobeen calibrated with HIPPARCOS data. It is clear that, in addition toastrophysical problems, there are also problems in the application ofHIPPARCOS data that are not yet fully understood. Table 1, whichcontains the basic data for the RR Lyraes, is available only at CDS. Itmay be retrieved via anonymous FTP at cdsarc.u-strasbg.fr (130.79.128.5)or via the Web at http://cdsweb.u-strasbg.fr/Abstract.html
| The impact of HIPPARCOS on the RR Lyrae Distance Scale
Not Available
| Multiperiodicity in the atypical delta SCT star AN Lyn
New uvby data collected of AN Lyn together with the reanalysis of olddata establish that this star is a multiperiodic pulsator. Threeindependent frequencies (nu _1=10.1756, nu _2=18.1309 and nu _3=9.5598cd(-1) ) and some interactions between them are found to be present inthe light curve. Changes in amplitude with a large time scale areconfirmed for the main frequency. Moreover, changes in amplitude arealso present for the secondary frequencies, especially for nu _3. Aftersubtraction of the secondary frequencies from the light curves, theclassical O-C method has been used to analyse the behaviour of the mainperiod. A comparison is made between AN Lyn and the other two knowndelta Sct stars with atypical light curves, i.e., V1719 Cyg and V798Cyg. New uvby data have been also collected for V1719 Cyg and the O-Cmethod has been used to analyse the behaviour of the main period. It isfound that the main pulsation of this star can be well described bymeans of a linear ephemeris with a period of P=0.(d) 26729700 over thelast eighteen years. Finally, analysis of the different data setsavailable in the literature do not reveal significative changes in theamplitude of the main frequency of V1719 Cyg. Table 5 will be accessibleonly in electronic form at the CDS
| Luminosities of SX Phoenicis, Large-Amplitude Delta Scuti, and RR Lyrae Stars
Strömgren _uvbyβ photometry of SX Phoenicis andlarge-amplitude δ Scuti variables is analyzed to determine themean temperatures, metal abundances, and surface gravities of the stars.The mean temperatures and fundamental periods are used in conjunctionwith the pulsation equation and stellar models to derive masses, radii,surface gravities, and M_bol of the variables. The stars exhibit aperiod-luminosity relation. With the aid of Hipparcos trigonometricparallaxes the zero-point of the M_v, p is set. We find M_v = -3.725 logP - 1.933. This P-L relation is utilized to find the M-v values of RRLyrae stars or horizontal-branch stars in globular clusters and theCarina galaxy-objects that contain both SX Phe, and RR Lyrae variables,or horizontal-branch stars. The M_v values of the metal-poor RR Lyraestars are found to be consistent with M_v [Fe/H] calibrations derived bySandage (1993) and by McNamara (1997) from revised Baade- Wesselink M_vvalues. At [Fe/H] = -1.9 M_v is 0.42. Feast and Catchpole (1997)suggestion that M_v = 0.25 at [Fe/H] = -1.9 for RR Lyrae is discussed.This M_v value is too luminous because it makes the (T_eff) of RR Lyraestoo high-well off any (T_eff) = _f (color index) calibration. (SECTION:Stars)
| Radial velocities and iron abundances of field RR Lyraes. I.
We present systemic velocities and iron abundances for 56 RR Lyraes, themajority of which have been observed by the HIPPARCOS satellite.Comparison between our systemic velocities and previous valuesidentifies several binary candidates only one of which, TU UMa, waspreviously suspected of being a binary. However, spectra of the unusualRR Lyrae BB Vir show no evidence of line doubling and hence do notsupport the recent claims that this star may have a Blue HorizontalBranch companion. Comparison between our abundances and previousdeterminations shows reasonable agreement except with the recent work of\cite[Layden (1994)]{Lay94} where we find systematic differences.Several of the stars included on the HIPPARCOS observing list as RRLyraes are shown to be mis-classified. Of particular interest are thestars V363 Cas and AT And which, by analogy with XZ Cet, may beanomalous Cepheids. The Appendix is available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A Photometric Study of V798 Cygni
New photometric $(uvby\beta)$ observations of the intrinsic variablestar V798 Cyg have been secured and used to derive values of foregroundreddening, E($b - y$) = 0\fm117, and metallicity, [Fe/H] = 0.64.Intrinsic ($b - y$) and $c1$ values indicate a mean effectivetemperature, $< Teff >$ = 7150 K, and a mean surfacegravity, $< \log g >$ = 3.39. Pulsation theory and theoreticalevolutionary tracks yield a mass of 2.3$M_{\odot}$ and an age of 0.63Gyrs. Although V798 Cyg has been described as being multi-periodic, thisconclusion is not confirmed by our observations. V798 Cyg in mostrespects resembles a typical population I dwarf Cepheid. (SECTION:Stars)
| AN Lyn: an unusual medium amplitude δ SCT star.
Simultaneous uvbyβ photometric observations of the medium amplitudeδ Sct star AN Lyn have been collected and new times of lightmaxima have been obtained. The Fourier transform and classical O-Cmethods are used to analyse the pulsation of this star. The light curvesare peculiar in the sense that the descending branches are steeper thanthe ascending ones. Amplitude variations are shown to be present fromseason to season. The analysis of the phase shifts between observedlight and colour variations suggests that this star is a radialpulsator. In addition, intrinsic b-y, m_1_ and c_1_ values are alsoderived and the physical parameters are determined indicating that thisvariable is a nearly cold and evolved δ Sct star showing solarmetal abundances and pulsating in the second overtone.
| Fourier Decomposition of the Light Curves of Three Dwarf Cepheids: CY Aquarii, XX Cygni, and V798 Cygni
The three dwarf Cepheid variable stars CY Aquarii, XX Cygni, and V798Cygni were examined with CCD time series ensemble photometry. TheFourier decomposition of the light curves showed no evidence that any ofthe three stars was a double-mode variable. CY Aqr was fit with a nineterm harmonic series with a residual error of 10 mmag. XX Cyg was fitwith a ten term harmonic series with a residual error of 10 mmag. V798Cyg was fit with a four term harmonic series with a residual error of 7mmag. In addition, we examined a set of double-mode dwarf Cepheids withthe same Fourier decomposition techniques. We present evidence thatthese double-mode dwarf Cepheids fill the gap in the amplitude ratiodistribution reported by Antonello et al.(1986) and Poretti et al.(1990.(SECTION: Stars)
| Spectroscopic survey of delta Scuti stars. I. Rotation velocities and effective temperatures
Projected rotational velocities and effective temperatures for 68 deltaSct stars as well as 41 non-variable stars of similar spectral type andluminosity are presented here. The rotational velocities have beencalculated following the method developed in \cite[Gray (1992)]{ref38}and effective temperatures have been derived using the Balmer lineprofiles. The temperatures obtained from this method are shown to be inreasonable agreement with those calculated using the Infrared FluxMethod (IRFM) or spectrophotometric methods. This result has allowed usto use our temperatures to compare different uvby beta photometriccalibrations. We find that the calibration given by \cite[Moon \&Dworetsky (1985)]{ref72} is the most consistent. In the second part ofthis paper we have studied the relation between the pulsationalproperties (periods and amplitudes) and the physical parameters (v sin iand Teff). Where pulsation modes have been determined, thelow amplitude $\delta$ Scutis tend to be multimode (radial andnon-radial) pulsators, consistent with the theory that non-linearcoupling between modes acts to limit the amplitude in these stars. Wehave compared the distribution of v sin i for low amplitude $\delta$Scutis and non-variable stars. This shows the $\delta$ Scutis have abroader distribution in v sin i suggesting that a high rotation velocitymay favour pulsation. We find that the large amplitude delta Scuti starstend to have longer periods, cooler temperatures and lower rotationvelocities. Given that the large amplitude stars are also relativelyrare all the above are consistent with the hypothesis that these starsare more evolved (sub-giants) than the low amplitude delta Scutis (mainsequence or early post-main sequence).
| Pulsation in high amplitude delta Scuti stars.
It has been pointed out by earlier authors that radial pulsation seemsto be the only type present in high amplitude δ Sct stars, atleast for monoperiodic stars. In order to confirm this or not, we havecollected all the multicolor data available for these stars in theStroemgren and Johnson photometric systems. Then, the type of pulsationhas been analysed on the basis of the phase shifts and amplitude ratiosbetween observed light and colour variations. The results indicate thatall the stars analysed, including both high amplitude δ Sct(Population I) and SX Phe (Population II) stars, are radial pulsators.This is also true for the monoperiodic medium amplitude δ Sctstars analysed.
| 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 catalogue of variable stars in the lower instability strip.
Identifications, positions, photometry, spectra, some pulsationalfeatures, other astrophysical parameters and literature for 302pulsating variable stars in the lower instability strip, near the ZAMS,are given. About 185 stars have near homogeneous photometric informationin the Stroemgren's uvby-β photometric system. Thiscatalogue/database covers information published until November 1993.
| δ Scuti stars: a new revised list
An extensive and up to date list of δ Sct stars is presented. Thiscatalogue is intended to be a comprehensive review of observationalcharacteristics of all the δ Sct stars known until now, includingstars contained in earlier catalogues together with other new discoveredvariables, covering information published until November 1993. Globalinformation in the form of histograms and diagrams are also shown.
| Kinematics of Sandage-Fouts stars in three cardinal directions
V and (B - V) for 429, 442, and 427 stars are observed in the directionsof the anticenter, Cygnus, and the NGP, respectively, and DDO colors forthose stars G0 and later. The samples observed are ones for whichSandage and Fouts (1987) have published radial velocities. W, V, and Wcomponents of space velocity are derived from DDO distances withavailable proper motions. A clear correlation was found to exist betweenthe velocity dispersions and Fe/H with the dispersions decreasing asFe/H increases to about + 0.00, where V then becomes significantlynegative. The 'thick disk' component is clearly recognized, with sigma(W) approximately equal to 36 km/sec. In the 'old thin disk' and the'young thin disk', 43 percent and 42 percent of the stars have negativeV values, respectively.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Κύκνος |
| Right ascension: | 21h04m32.92s |
| Declination: | +50°47'03.3" |
| Apparent magnitude: | 7.995 |
| Distance: | 233.645 parsecs |
| Proper motion RA: | -2.7 |
| Proper motion Dec: | -5.7 |
| B-T magnitude: | 8.487 |
| V-T magnitude: | 8.036 |
Catalogs and designations:
|
