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Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes
We present a method which separates field dwarfs and field giants bytheir 2MASS and V apparent magnitudes. This method is based onspectroscopically selected standards and is hence reliable. We appliedit to stars in two fields, SA 54 and SA 82, and we estimated a full setof Galactic model parameters for giants including their total localspace density. Our results are in agreement with the ones given in therecent literature.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/165}
| Evidence for Low-dimensional Chaos in Semiregular Variable Stars
We present an analysis of the photometric observations of the lightcurves of the five large-amplitude, irregularly pulsating stars R UMi,RS Cyg, V CVn, UX Dra, and SX Her. First, multiperiodicity is eliminatedfor these pulsations; i.e., they are not caused by the excitation of asmall number of pulsation modes with constant amplitudes. Next, on thebasis of energetics we also eliminate stochasticity as a cause, leavinglow-dimensional chaos as the only alternative. We then use a global flowreconstruction technique in an attempt to extract quantitativeinformation from the light curves and to uncover common physicalfeatures in this class of irregular variable stars that straddle the RVTau to the Mira variables. Evidence is presented that the pulsationalbehavior of R UMi, RS Cyg, V CVn, and UX Dra takes place in afour-dimensional dynamical phase space, suggesting that two vibrationalmodes are involved in the pulsation. A linear stability analysis of thefixed points of the maps further indicates the existence of a two-moderesonance, similar to the one we had uncovered earlier in R Sct. Theirregular pulsations are the result of a continual energy exchangebetween two strongly nonadiabatic modes, a lower frequency pulsationmode and an overtone that are in a close 2:1 resonance. The evidence isparticularly convincing for R UMi, RS Cyg, and V CVn, but much weakerfor UX Dra. In contrast, the pulsations of SX Her appear to be morecomplex and may require a six-dimensional space.
| Self-Correlation Studies of RV Tauri Variables and Related Objects
RV Tauri (RVT) variables are old, low-mass, yellow supergiant pulsatingvariable stars whose light curves show alternating deep and shallowminima. They are related to Population II Cepheid (CW) variables and toyellow semiregular (SRD) variables. We describe the results ofself-correlation analysis of a large body of visual photometry of 9bright RVT and SRd variables, namely AG Aur, AV Cyg, SU Gem, AC Her, SXHer, TT Oph, UZ Oph, TX Per, and V Vul. Self-correlation analysis, whichprobes the cycle-to-cycle behavior of a variable, averaged over adataset, has proven to be a useful tool for investigating these stars,because their classification is actually based on their cycle-to-cyclebehavior. Our results are consistent with those of our analysis of RVTand CW variables in the Large Magellanic Cloud (Percy, Hosic, and Leigh2003), and support the view that the RV Tauri phenomenon has twodimensions: (i) the relative depths of the primary and secondary minima,and (ii) the number of cycles over which the alternating minimacorrelate. If the RVT phenomenon is due to the presence of two pulsationmodes, then these dimensions are equivalent to: (i) the relativeamplitudes of the two modes, and (ii) the closeness of the ratio of thepulsation periods to 2:1. There is therefore a "spectrum" of behaviorfrom CW to RVT to SRd, depending on the values of these two parameters.
| A weakly non-adiabatic one-zone model of stellar pulsations: application to Mira stars
There is growing observational evidence that the irregular changes inthe light curves of certain variable stars might be due to deterministicchaos. Supporting these conclusions, several simple models of non-linearoscillators have been shown to be capable of reproducing the observedcomplex behaviour. In this paper, we introduce a non-linear,non-adiabatic one-zone model intended to reveal the factors leading toirregular luminosity variations in some pulsating stars. We have studiedand characterized the dynamical behaviour of the oscillator as the inputparameters are varied. The parametric study implied values correspondingto stellar models in the family of long period variables and inparticular of Mira-type stars. We draw attention to certain solutionsthat reproduce with reasonable accuracy the observed behaviour of somepeculiar Mira variables.
| Spectroscopic Binaries, Velocity Jitter, and Rotation in Field Metal-poor Red Giant and Red Horizontal-Branch Stars
We summarize 2007 radial velocity measurements of 91 metal-poor fieldred giants. Excluding binary systems with orbital solutions, ourcoverage averages 13.7 yr per star, with a maximum of 18.0 yr. We reportfour significant findings. (1) Sixteen stars are found to bespectroscopic binaries, and we present orbital solutions for 14 of them.The spectroscopic binary frequency of the metal-poor red giants, with[Fe/H]<=-1.4, for periods less than 6000 days, is 16%+/-4%, which isnot significantly different from that of comparable-metallicity fielddwarfs, 17%+/-2%. The two CH stars in our program, BD -1°2582 and HD135148, are both spectroscopic binaries. (2) Velocity jitter is presentamong about 40% of the giants with MV<=-1.4. The twobest-observed cases, HD 3008 and BD +22°2411, showpseudoperiodicities of 172 and 186 days, longer than any knownlong-period variable in metal-poor globular clusters. Photometricvariability seen in HD 3008 and three other stars showing velocityjitter hints that starspots are the cause. However, the phasing of thevelocity data with the photometry data from Hipparcos is not consistentwith a simple starspot model for HD 3008. We argue against orbitalmotion effects and radial pulsation, so rotational modulation remainsthe best explanation. The implied rotational velocities for HD 3008 andBD +22°2411, both with MV<=-1.4 and R~50Rsolar, exceed 12 km s-1. (3) Including HD 3008and BD +22°2411, we have found signs of significant excess linebroadening in eight of the 17 red giants with MV<=-1.4,which we interpret as rotation. In three cases, BD +30°2034, CD-37°14010, and HD 218732, the rotation is probably induced by tidallocking between axial rotation and the observed orbital motion with astellar companion. But this cannot explain the other five stars in oursample that display signs of significant rotation. This high frequencyof elevated rotational velocities does not appear to be caused bystellar mass transfer or mergers: there are too few main-sequencebinaries with short enough periods. We also note that the lack of anynoticeable increase in mean rotation at the magnitude level of the redgiant branch luminosity function ``bump'' argues against the rapidrotation's being caused by the transport of internal angular momentum tothe surface. Capture of a planetary-mass companion as a red giantexpands in radius could explain the high rotational velocities. (4) Wealso find significant rotation in at least six of the roughly 15 (40%)red horizontal-branch stars in our survey. It is likely that theenhanced rotation seen among a significant fraction of both blue and redhorizontal-branch stars arose when these stars were luminous red giants.Rapid rotation alone therefore appears insufficient cause to populatethe blue side of the horizontal branch. While the largest projectedrotational velocities seen among field blue and red horizontal-branchstars are consistent with their different sizes, neither are consistentwith the large values we find for the largest red giants. This suggeststhat some form of angular momentum loss (and possibly mass loss) hasbeen at work. Also puzzling is the apparent absence of rotation seen infield RR Lyrae variables. Angular momentum transfer and conservation inevolved metal-poor field stars thus pose many interesting questions forthe evolution of low-mass stars.
| Studies of the RV Tauri phenomenon.
Not Available
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 166: HR 2054 and 7 Lyncis
Not Available
| Period-doubling events in the light curve of R Cygni: Evidence for chaotic behaviour
A detailed analysis of the century long visual light curve of thelong-period Mira star R Cygni is presented and discussed. The data werecollected from the publicly available databases of the AFOEV, the BAAVSSand the VSOLJ. The full light curve consists of 26655 individual pointsobtained between 1901 and 2001. The light curve and its periodicity wereanalysed with help of the O-C diagram, Fourier analysis andtime-frequency analysis. The results demonstrate the limitations ofthese linear methods. The next step was to investigate the possiblepresence of low-dimensional chaos in the light curve. For this, asmoothed and noise-filtered signal was created from the averaged dataand with the help of time delay embedding, we have tried to reconstructthe attractor of the system. The main result is that R Cygni shows suchperiod-doubling events that can be interpreted as being caused by arepetitive bifurcation of the chaotic attractor between a period 2Torbit and chaos. The switch between these two states occurs in a certaincompact region of the phase space, where the light curve ischaracterized by ~ 1500-day long transients. The Lyapunov spectrum wascomputed for various embedding parameters confirming the chaoticattractor, although the exponents suffer from quite high uncertaintybecause of the applied approximation. Finally, the light curve iscompared with a simple one zone model generated by a third-orderdifferential equation which exhibits well-expressed period-doublingbifurcation. The strong resemblance is another argument for chaoticbehaviour. Further studies should address the problem of global flowreconstruction, including the determination of the accurate Lyapunovexponents and dimension.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Polarimetry of 167 Cool Variable Stars: Data
Multicolor photoelectric polarimetry is presented for 167 stars, most ofwhich are variable stars. The observations constitute a data set thatfor some stars covers a time span of 35 yr. Complex variations are foundover time and wavelength and in both the amount of polarization and itsposition angle, providing constraints for understanding the polarizingenvironments in and around these cool stars.
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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.
| 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.
| Speckle Interferometry of New and Problem HIPPARCOS Binaries
The ESA Hipparcos satellite made measurements of over 12,000 doublestars and discovered 3406 new systems. In addition to these, 4706entries in the Hipparcos Catalogue correspond to double star solutionsthat did not provide the classical parameters of separation and positionangle (rho,theta) but were the so-called problem stars, flagged ``G,''``O,'' ``V,'' or ``X'' (field H59 of the main catalog). An additionalsubset of 6981 entries were treated as single objects but classified byHipparcos as ``suspected nonsingle'' (flag ``S'' in field H61), thusyielding a total of 11,687 ``problem stars.'' Of the many ground-basedtechniques for the study of double stars, probably the one with thegreatest potential for exploration of these new and problem Hipparcosbinaries is speckle interferometry. Results are presented from aninspection of 848 new and problem Hipparcos binaries, using botharchival and new speckle observations obtained with the USNO and CHARAspeckle cameras.
| Polarimetric and Photometric Observations of Long-Period Variables
Not Available
| IRAS Detections of Metal-poor Red Giants
A number of relatively bright metal-poor red giants from the HD and BDcatalogs are found to have been detected by the IRAS satellite. Data forthese stars have been retrieved from the IRAS Point Source Catalog (PSC)and/or the Faint Source Catalog (FSC). The majority of metal-poor giantsin these samples fall along relatively well-defined sequences in plotsof V-[12] versus B-V and V-I; for these stars, the 12 μm fluxdetected is presumed to arise from the photosphere. Only a subset ofstars detected at 12 μm were detected at 25 μm these are displayedin a plot of [12]-[25] versus V-[12]. There are a small number of giantsthat exhibit notable 12 and/or 25 μm excesses relative to the meansequences defined by the bulk of the sample. Those stars with the mostunambiguous evidence for infrared excesses are variable stars, eitherlong-period or semiregular variables or RV Tauri stars. As such, thosestars exhibiting infrared excesses in the metal-poor giant sample arelikely in the asymptotic giant branch (AGB) or post-AGB phase ofevolution. There is no clear evidence for nonvariable first-ascent redgiants having been detected among the infrared-excess stars. In fact,some metal-poor red giants known to exhibit outflows in theirchromospheres do not show infrared excesses. A Population II starascending the red giant branch for the first time appears to have toolow a mass-loss rate to be recognizable as an infrared-excess star inthe IRAS PSC or FSC.
| The Chemical Compositions of the SRd Variable Stars. I. XY Aquarii, RX Cephei, AB Leonis, and SV Ursae Majoris
Chemical compositions are derived from high-resolution spectra for fourstars classed as SRd variables in the General Catalogue of VariableStars. Two stars-XY Aquarii and RX Cephei-are of solar metallicity andmost likely not variable stars. Their spectroscopic effectivetemperatures and surface gravities correspond to the spectral types G0 Vfor XY Aqr and G8 III for RX Cep. Two stars are undisputed variables andshown here to be metal-poor supergiants: AB Leonis with [Fe/H] ~=-1.6and SV Ursae Majoris with [Fe/H] ~=-1.4. The metallicities and highradial velocities show them to be halo stars.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Atmospheric conditions in yellow and red variables
Pulsation occurs in late-type giant and supergiant stars under a widerange of atmospheric conditions and evolutionary stages. Longobservational baselines are necessary to distinguish pulsationbehaviors. Spectrographic and photometric observations of a variety oflate-type pulsators are considered in the context of light-curvetaxonomy and changing atmospheric conditions.
| Polarimetric observations of pulsating variable stars
Results are presented for polarimetric observations of 17 red giants andsupergiants, of which nine are long-period Mira variables, five aresemiregular variables (SR), and three are slowly fluctuating variables(Lb). Light polarization is detected for eight stars, seven of them forthe first time.
| 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.
| 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.
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&db_key=AST
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| 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.
| The nature of RV Tauri variables. I - Spectrophotometric atlas of selected field stars
Multiphase observations of a selected sample of field RV Tauri variablesare presented, consisting of 10-A resolution spectrophotometry in the3500-6200-A wavelength range. The data confirm the previous suggestionthat most of the RV Tau variables exhibit clear deviations from normalsupergiants which cannot be related simply to metallicity. Evidence isfound for strong molecular absorption (CN for AC Her and EP Lyr; TiO forR Sct and V Vul) at phases where the inferred stellar temperature isinconsistent with such absorption, possibly due to atmospheric shockswhich arise in at least two separate episodes (most notably, in the risefrom primary and secondary minimum).
| Determination of effective temperatures and surface gravities of metal-deficient K-G giants in the Vilnius photometric system
Not Available
| The kinematics of halo red giants
The present 337 radial velocities were obtained with typical accuraciesof 0.7 cm km/sec for 85 metal-poor field red giants, selected from thekinematically unbiased samples of Bond (1980) and Bidelman and MacConnel(1973). The multiply-observed stars suggest the field halo binaryfraction exceeds 10 percent. Using these velocities and those publishedby others, a sample of 174 red giants with Fe/H of not more than -1.5 isobtained. Their mean motion with respect to the local standard of restis -206 + or - 23 km/sec, and the velocity dispersions are sigma (R) of154 + or - 18 km/sec, sigma(theta) of 102 + or - 27 km/sec, andsigma(phi) of 107 + or - 15 km/sec. Using photometrically derivedabsolute magnitudes and published proper motions, orbital eccentricitiesare computed for 72 stars not already considered in a similar study ofsouthern stars by Norris et al. (1985). A few stars with e of less than0.4 are found.
| A catalogue of Fe/H determinations, 1984 edition
The present version of the Cayrel de Strobel et al. (1981) catalog ofFe/H abundance ratio determinations contains 1921 values for 1035 stars,which represents an augmentation over the previous publication of 48 and47 percent, respectively. In addition, the literature search conductedis complete up to December, 1983. Stellar metal abundance, effectivetemperature, spectroscopic gravity, spectral type, and photometricindices are covered.
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Osservazione e dati astrometrici
| Costellazione: | Ercole |
| Ascensione retta: | 16h07m27.25s |
| Declinazione: | +24°54'29.9" |
| Magnitudine apparente: | 8.351 |
| Distanza: | 515.464 parsec |
| Moto proprio RA: | -15.2 |
| Moto proprio Dec: | -36.8 |
| B-T magnitude: | 10.388 |
| V-T magnitude: | 8.52 |
Cataloghi e designazioni:
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