Variable Stars in NSVS Database I. 86 New Variables in Andromeda
A search for light curves with variability in the NSVS data was carriedout in a 46 square-degree area in Andromeda. The field contains 51955light curves. We found 136 variables, 86 of them were not knownpreviously. Extrapolating the density of the variables in the field tothe whole NSVS, the total number of variables in the survey is estimatedto be 52000 - 61000.
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Chemical composition of semi-regular variable giants
Aims.The aim of this work was to derive chemical abundances in 5 starsthat were previously reported to be SRd variable stars from the halopopulation, and, in particular, to check if manganese does showsignificant underabundance in our program stars similar to that of TYVir, first detected by Luck & Bond. Methods: Elemental abundanceshave been found through the LTE and NLTE analyses, applied tohigh-resolution (R˜50 000) spectra. Results: We have derived theabundances of 18 chemical elements in RX Vir, AB Leo, CK Vir, SV UMa,and TY Vir, and made the following conclusions. Conclusions: .RX Vir isa typical solar-like star. Its classification as a halo population SRdvariable star should be ruled out. The remaining four stars of ourprogram have chemical composition and fundamental parameters thatconfirm their status as metal-deficient halo giants. All studied SRdgiants have relative-to-solar elemental abundances typical of the fieldhalo stars of metallicity -1.8. There is only one exception, which isthe relative manganese abundance. All SRd program stars show uniform[Mn/Fe] ratios that are typical of the stars with metallicity [Fe/H]≈ -3.5. The reason for such a low manganese abundance in these starsis unknown.Based on observations obtained at the Canada-France-Hawaii Telescope(CFHT), which is operated by the National Research Council of Canada,the Institute National des Sciences de l'Univers of the Centre Nationalde la Recherche Scientifique of France, and the University of Hawaii.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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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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The Chemical Compositions of the SRD Variable Stars. III. KK Aquilae, AG Aurigae, Z Aurigae, W Leo Minoris, and WW Tauri
Chemical compositions are derived from high-resolution spectra for fivefield SRd variables. These supergiants not previously analyzed are shownto be metal poor: KK Aql with [Fe/H]=-1.2, AG Aur with [Fe/H]=-1.8, ZAur with [Fe/H]=-1.4, W LMi with [Fe/H]=-1.1, and WW Tau with[Fe/H]=-1.1. Their compositions are, except for two anomalies, identicalto within the measurement errors to the compositions of subdwarfs,subgiants, and less evolved giants of the same [Fe/H]. One anomaly is ans-process enrichment for KK Aql, the first such enrichment reported foran SRd variable. The second and more remarkable anomaly is a stronglithium enrichment for W LMi, also a first for field SRd variables. TheLi I λ6707 profile is not simply that of a photospheric line butincludes strong absorption from redshifted gas, suggesting, perhaps,that lithium enrichment results from accretion of Li-rich gas. Thispotential clue to lithium enrichment is discussed in light of variousproposals for lithium synthesis in evolved stars.
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Studies of Yellow Semiregular(SRd) Variables
We have used the Hipparcos database of epoch photometry to study thevariability of several yellow semiregular(SRd) variables. For some ofthe stars (V847 Cas, RW Cep, BM Sco, CE Vir), the results wereinconclusive. For SX Lac and TY Vir, the periods found were consistentwith the General Catalogue of Variable Stars (190 and 50 daysrespectively). For UU Her, the known periods of about 45 and 72 dayswere recovered. For WY And, RU Cep, and SX Her, reliable periods werefound; we used archival data to construct (O-C) diagrams to study boththe random and systematic period changes in these three stars.
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The Chemical Compositions of the SRD Variable Stars. II. WY Andromedae, VW Eridani, and UW Librae
Chemical compositions are derived from high-resolution spectra for threestars classed as SRd variables in the General Catalogue of VariableStars. These stars are shown to be metal-poor supergiants: WY And with[Fe/H]=-1.0, VW Eri with [Fe/H]=-1.8, and UW Lib with [Fe/H]=-1.2. Theircompositions are identical to within the measurement errors to thecompositions of subdwarfs, subgiants, and less evolved giants of thesame [Fe/H]. The stars are at the tip of the first giant branch or inthe early stages of evolution along the asymptotic giant branch (AGB).There is no convincing evidence that these SRd variables areexperiencing thermal pulsing and the third dredge-up on the AGB. The SRdvariables appear to be at the cool limit of the sequence of RV Taurivariables.
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Classification of Population II Stars in the Vilnius Photometric System. I. Methods
The methods used for classification of Population II stars in theVilnius photometric system are described. An extensive set of standardswith known astrophysical parameters compiled from the literature sourcesis given. These standard stars are classified in the Vilnius photometricsystem using the methods described. The accuracy of classification isevaluated by a comparison of the astrophysical parameters derived fromthe Vilnius photometric system with those estimated from spectroscopicstudies as well as from photometric data in other systems. For dwarfsand subdwarfs, we find a satisfactory agreement between our reddeningsand those estimated in the uvbyscriptstyle beta system. The standarddeviation of [Fe/H] deter mined in the Vilnius system is about 0.2 dex.The absolute magnitude for dwarfs and subdwarfs is estimated with anaccuracy of scriptstyle <=0.5 mag.
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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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Professional-amateur collaboration in variable star research: V. Observations of yellow semi-regular variables
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V487 Cassiopeiae (HD 6474): a UU Herculis variable in the galactic plane?
New photoelectric photometry of V487 Cassiopeiae (HD 6474) made between1984 and 1992 is presented. The star has a rather complicated lightvariation: at least two periods (P1 = 160.3 days andP2 = 99.6 days) are present in the light curve, one of thempossibly with variable amplitude. The period ratio(P2/P1 = 0.62) and the nature of the lightvariation (i.e. the simultaneous presence of two modes, the amplitudechange) are both very similar to that of UU Herculis. This similarityindicates that V487 Cassiopeiae is a UU Her-type variable though it isin the galactic plane. A distinction between the UU Her-type and 89Her-type variables is suggested.
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The reddening of type AB RR Lyrae stars
The paper modifies Sturch's (1966) method for deriving, from observednear-minimum light colors, EB-V values for RR Lyrae starswith Bailey's types for a or b light curves in order to avoid the use ofreddening and metallicity-sensitive U-B colors. The Delta(S), (Fe/H)calibration is examined, and blanketing corrections are derived fromsynthetic colors of models by Kurucz (1975, 1979). Sturch's finding thatthe intrinsic blanketing-corrected near-minimum light B-V color of avariable can be estimated from its period is verified. The inherentaccuracy of the method is discussed and found to depend appreciably oncycle-to-cycle color variations. Comparisons are made with otherreddening determinations. The blanketing corrections determined bySturch from delta(U-B) values are found to make his EB-Vvalues less than those found in the present study, while his estimatedintrinsic colors make his EB-V values greater than thosefound in this study.
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Classification of Population II supergiants and related stars in the Vilnius system
The results of photometric classification in the Vilnius system of 117Population II supergiants, suspected supergiants, and related stars aregiven. Their photometric spectral types, intrinsic color indices (Y-V)0,color excesses E(Y-V), metallicities Fe/H, and absolute magnitudes MVare determined. It is shown that the system allows us to detect the UUHerculis-type supergiants photometrically. The analyzed SRd star samplefalls into two groups of metallicity and luminosity. Our photometricclassification assigns luminosity classes from III to V to 37 F-K starswith /b/ greater than 16 deg classified by Bartaya (1979) from objectiveprism spectra as supergiants.
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Chaotic behavior in nonlinear radial oscillations of one-zone stellar models
Nonlinear radial oscillations of one-zone stellar models wereinvestigated. The nonlinear oscillation of Baker's (1986) modelbifurcates and develops into chaos through period-doubling, when thesaturation of the excitation mechanism for pulsation is taken intoaccount. First return maps were compared with those derived from theobservational materials of RV Tauri stars and other semiregular variablestars. The complex feature of observed return maps seems to fit those ofthe nonlinear one-zone model.
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Factor analysis of the DDO colours of RV Tauri and SRd stars
The properties of RV Tauri and SRd stars in the DDO photometric systemhave been examined by means of the factor analysis. Within the limitsdue to the restricted sample, this analysis supports the spectroscopicclassification of these objects, and confirms the usefulness of the DDOphotometry to study them. Some objects with peculiar characteristics arediscussed.
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On the similarity of the statistics of high-velocity clouds and stars of the spherical component of the Galaxy
An account is given of a comparison, for the first time, ofhigh-velocity H I clouds (HVCs) with objects of the spherical subsystemof the Galaxy. The dependence of the radial velocities of the HVCs ongalactic longitude is similar to Stromberg's asymmetry. The galacticrotational velocity and the velocity dispersion of the HVCs are the sameas for the objects of the spherical subsystem (subdwarfs, RR Lyraevariables, globular clusters). Like the subdwarfs near them, the HVCs donot exhibit a concentration near the center of the Galaxy. There areelongated groups of stars, including Kapteyn's group, that are projectedonto (or are in the neighborhood of) C II, the 'Magellanic Stream', andother complexes with the same radial velocities as these HVCs. Thedistances of the majority of the stars of these groups are on the orderof 100 pc.
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Three-dimensional calssification of F-M type halo stars in the Vilnius photometric system
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A photometric investigation of RV Tauri and yellow semiregular variables
Results are presented for DDO and UBV photoelectric photometry of 52 RVTau and semiregular variables and candidates. CN abundances, effectivetemperatures, surface gravities, absolute visual magnitudes, and massestimates are derived in the framework of the spectroscopic groupingsproposed by Preston et al. (1963). The photometry suggests a furtherdivision of Preston's group A, and a possible physical connection isindicated between this group and the semiregular variables. Thespectroscopic groups are shown to be well separated in the DDOcolor-color diagrams when mean colors are used for individual stars. Anupper limit of about 3 solar masses is determined for stars in eachgroup. A correlation between derived iron abundances and published IRexcesses obtained from flux measurements at 3.6 and 11.3 microns isfound which supports the contention that dust production incircumstellar shells increases with increasing metallicity.
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Mean absolute magnitude of the RR Lyrae stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&A....24..313H
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On the Interpretation of the Motions of the Mira Variables
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Investigation of the polarization of radiation of variable stars. I.
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Reversal of the Bright H? Line in the Spectrum of T Centauri
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The Spectrum of BD+67°922.
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The Semiregular Variable Stars of the RV Tauri and Related Classes.
Abstract image available at:http://adsabs.harvard.edu/abs/1952ApJ...115...25J
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The Spectra of Variables of the RV Tauri and Yellow Semiregular Types.
Abstract image available at:http://adsabs.harvard.edu/abs/1951ApJ...113...60R
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Spectra of Ninety-four Variable Stars
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