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Random forest automated supervised classification of Hipparcos periodic variable stars
We present an evaluation of the performance of an automatedclassification of the Hipparcos periodic variable stars into 26 types.The sub-sample with the most reliable variability types available in theliterature is used to train supervised algorithms to characterize thetype dependencies on a number of attributes. The most useful attributesevaluated with the random forest methodology include, in decreasingorder of importance, the period, the amplitude, the V-I colour index,the absolute magnitude, the residual around the folded light-curvemodel, the magnitude distribution skewness and the amplitude of thesecond harmonic of the Fourier series model relative to that of thefundamental frequency. Random forests and a multi-stage scheme involvingBayesian network and Gaussian mixture methods lead to statisticallyequivalent results. In standard 10-fold cross-validation (CV)experiments, the rate of correct classification is between 90 and 100per cent, depending on the variability type. The main mis-classificationcases, up to a rate of about 10 per cent, arise due to confusion betweenSPB and ACV blue variables and between eclipsing binaries, ellipsoidalvariables and other variability types. Our training set and thepredicted types for the other Hipparcos periodic stars are availableonline.
| The luminosities and distance scales of type II Cepheid and RR Lyrae variables
Infrared and optical absolute magnitudes are derived for the type IICepheids κ Pav and VY Pyx using revised Hipparcos parallaxes andfor κ Pav, V553 Cen and SW Tau from pulsational parallaxes.Revised Hipparcos and HST parallaxes for RR Lyrae agree satisfactorilyand are combined in deriving absolute magnitudes. Phase-corrected J, Hand Ks mags are given for 142 Hipparcos RR Lyraes based onTwo-Micron All-Sky Survey observations. Pulsation and trigonometricalparallaxes for classical Cepheids are compared to establish the bestvalue for the projection factor (p) used in pulsational analyses.The MV of RR Lyrae itself is 0.16 +/- 0.12 mag brighter thanpredicted from an MV-[Fe/H] relation based on RR Lyrae starsin the Large Magellanic Cloud (LMC) at a modulus of 18.39 +/- 0.05 asfound from classical Cepheids. This is consistent with the prediction ofCatelan & Cortés that it is overluminous for its metallicity.The results for the metal- and carbon-rich Galactic disc stars, V553 Cenand SW Tau, each with small internal errors (+/-0.08 mag) have a meandeviation of only 0.02 mag from the period-luminosity (PL) relationestablished by Matsunaga et al. for type II Cepheids in globularclusters and with a zero-point based on the same LMC-scale. Comparingdirectly the luminosities of these two stars with published data on typeII Cepheids in the LMC and in the Galactic bulge leads to an LMC modulusof 18.37 +/- 0.09 and a distance to the Galactic Centre of R0= 7.64 +/- 0.21kpc. The data for VY Pyx agree with these results withinthe uncertainties set by its parallax. Evidence is presented thatκ Pav may have a close companion and possible implications of thisare discussed. If the pulsational parallax of this star is incorporatedin the analyses, the distance scales just discussed will be increased by~0.15 +/- 0.15 mag. V553 Cen and SW Tau show that at optical wavelengthsPL relations are wider for field stars than for those in globularclusters. This is probably due to a narrower range of masses in thelatter case.
| The Recent Period Evolution of the RRc stars HY Com, RU Psc and AP Ser
The first overtone RR Lyrae stars HY Com, RU Psc and AP Ser have shownfrequent sudden period changes in recent years, as calculated from NSVSand ASAS-3 data.
| Korrekturen zu Vorhersagen im BAV Circular 2008.
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| Laszlo Detre and the Konkoly Observatory
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| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| A catalogue of RR Lyrae stars from the Northern Sky Variability Survey
A search for RR Lyrae stars has been conducted in the publicly availabledata of the Northern Sky Variability Survey. Candidates have beenselected by the statistical properties of their variation; the standarddeviation, skewness and kurtosis with appropriate limits determined froma sample 314 known RRab and RRc stars listed in the General Catalogue ofVariable Stars. From the period analysis and light-curve shape of over3000 candidates 785 RR Lyrae have been identified of which 188 arepreviously unknown. The light curves were examined for the Blazhkoeffect and several new stars showing this were found. Six double-mode RRLyrae stars were also found of which two are new discoveries. Somepreviously known variables have been reclassified as RR Lyrae stars andsimilarly some RR Lyrae stars have been found to be other types ofvariable, or not variable at all.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| 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.
| RR Lyrae stars: kinematics, orbits and z-distribution
RR Lyrae stars in the Milky Way are good tracers to study the kinematicbehaviour and spatial distribution of older stellar populations. Arecently established well documented sample of 217 RR Lyr stars withV<12.5 mag, for which accurate distances and radial velocities aswell as proper motions from the Hipparcos and Tycho-2 catalogues areavailable, has been used to reinvestigate these structural parameters.The kinematic parameters allowed to calculate the orbits of the stars.Nearly 1/3 of the stars of our sample have orbits staying near the MilkyWay plane. Of the 217 stars, 163 have halo-like orbits fulfilling one ofthe following criteria: Θ < 100 km s-1, orbiteccentricity >0.4, and normalized maximum orbital z-distance>0.45. Of these stars roughly half have retrograde orbits. Thez-distance probability distribution of this sample shows scale heightsof 1.3±0.1 kpc for the disk component and 4.6±0.3 kpc forthe halo component. With our orbit statistics method we found a(vertical) spatial distribution which, out to z=20 kpc, is similar tothat found with other methods. This distribution is also compatible withthe ones found for blue (HBA and sdB) halo stars. The circular velocityΘ, the orbit eccentricity, orbit z-extent and [Fe/H] are employedto look for possible correlations. If any, it is that the metal poorstars with [Fe/H] <1.0 have a wide symmetric distribution aboutΘ=0, thus for this subsample on average a motion independent ofdisk rotation. We conclude that the Milky Way possesses a halo componentof old and metal poor stars with a scale height of 4-5 kpc having randomorbits. The presence in our sample of a few metal poor stars (thus partof the halo population) with thin disk-like orbits is statistically notsurprising. The midplane density ratio of halo to disk stars is found tobe 0.16, a value very dependent on proper sample statistics.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| RR Lyrae Sterne und ihre Bahnen in der Galaxis.
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| Unterschiedliche Helligkeitsauspragungen des Blazhko-Effectes.
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| Periode des Blazhko-Effektes im BAV Circular 2003.
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| Metallicities for Double-Mode RR Lyrae Stars in the Large Magellanic Cloud
Metallicities for six double-mode RR Lyrae stars (RRd's) in the LargeMagellanic Cloud have been estimated using the ΔS method. Thederived [Fe/H] values are in the range [Fe/H]=-1.09 to -1.78 (or -0.95to -1.58, adopting a different calibration of [Fe/H] versus ΔS).Two stars in our sample are at the very metal-rich limit of all RRd'sfor which metal abundance has been estimated, either by direct measure(for field objects) or on the basis of the hosting system (for objectsin globular clusters or external galaxies). These metal abundances,coupled with mass determinations from pulsational models and thePetersen diagram, are used to compare the mass-metallicity distributionof field and cluster RR Lyrae variables. We find that field and clusterRRd's seem to follow the same mass-metallicity distribution, within theobservational errors, strengthening the case for uniformity ofproperties between field and cluster variables. At odds to what isusually assumed, we find no significant difference in mass for RR Lyraevariables in globular clusters of different metallicity and Oosterhofftypes, or there may even be a difference contrary to the commonlyaccepted one, depending on the metallicity scale adopted to derive themasses. This ``unusual'' result for the mass-metallicity relation isprobably due, at least in part, to the inclusion of updated opacitytables in the computation of metal-dependent pulsation models. Based onobservations collected at the European Southern Observatories, Chile.
| 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.
| Kinematics of Metal-poor Stars in the Galaxy. II. Proper Motions for a Large Nonkinematically Selected Sample
We present a revised catalog of 2106 Galactic stars, selected withoutkinematic bias and with available radial velocities, distance estimates,and metal abundances in the range -4.0<=[Fe/H]<=0.0. This updateof the 1995 Beers & Sommer-Larsen catalog includes newly derivedhomogeneous photometric distance estimates, revised radial velocitiesfor a number of stars with recently obtained high-resolution spectra,and refined metallicities for stars originally identified in the HKobjective-prism survey (which account for nearly half of the catalog)based on a recent recalibration. A subset of 1258 stars in this cataloghave available proper motions based on measurements obtained with theHipparcos astrometry satellite or taken from the updated AstrographicCatalogue (second epoch positions from either the Hubble Space TelescopeGuide Star Catalog or the Tycho Catalogue), the Yale/San Juan SouthernProper Motion Catalog 2.0, and the Lick Northern Proper Motion Catalog.Our present catalog includes 388 RR Lyrae variables (182 of which arenewly added), 38 variables of other types, and 1680 nonvariables, withdistances in the range 0.1 to 40 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
| Early evolution of the Galactic halo revealed from Hipparcos observations of metal-poor stars
The kinematics of 122 red giant and 124 RR Lyrae stars in the solarneighborhood are studied using accurate measurements of their propermotions obtained by the Hipparcos astrometry satellite, combined withtheir published photometric distances, metal abundances, and radialvelocities. A majority of these sample stars have metal abundances of(Fe/H) = -1 or less and thus represent the old stellar populations inthe Galaxy. The halo component, with (Fe/H) = -1.6 or less, ischaracterized by a lack of systemic rotation and a radially elongatedvelocity ellipsoid. About 16 percent of such metal-poor stars have loworbital eccentricities, and we see no evidence of a correlation between(Fe/H) and e. Based on the model for the e-distribution of orbits, weshow that this fraction of low-e stars for (Fe/H) = -1.6 or less isexplained by the halo component alone, without introducing the extradisk component claimed by recent workers. This is also supported by theabsence of a significant change in the e-distribution with height fromthe Galactic plane. In the intermediate-metallicity range, we find thatstars with disklike kinematics have only modest effects on thedistributions of rotational velocities and e for the sample at absolutevalue of z less than 1 kpc. This disk component appears to constituteonly 10 percent for (Fe/H) between -1.6 and -1 and 20 percent for (Fe/H)between -1.4 and -1.
| Structural Properties of Pulsating Star Light Curves Through Fuzzy Divisive Hierarchical Clustering
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| Photoelectric Minima and Maxima of Selected Eclipsing and Pulsating Variables
Not Available
| The Rotation of RR Lyrae Stars
We report upper limits to rotation from the measurement of line breadthsvia cross-correlation analysis for 27 RR Lyrae variables. The eightbest-observed stars of type RRab show the same variation of breadth withphase: the breadth peaks sharply during the rise to maximum light, dropsgradually, and reaches a broad minimum during the phase of maximumradius. During this phase the breadth is always narrow, consistent withinstrumental resolution and turbulence alone. For the threewell-observed RRc variables, the breadth is this narrow at all phasesexcept for a slight increase during the rise to maximum light. Theremaining stars also conform to these patterns, albeit with sparse phasecoverage and lower signal-to-noise ratio. We interpret these results asindicating that lines are broadened in RRab stars by shock-inducedplumes or turbulence during the rise to maximum light, and perhaps byother causes as well, but not by rotation in RR Lyrae stars of eithertype. We estimate an upper limit of v sin i < 10 km s-1 in all cases.This is in stark contrast to the rotation seen in field blue horizontalbranch stars, where v sin i > 10 km s-1 in three out of sixwell-studied field stars, and to the more rapid rotation, oftenexceeding 100 km s-1, of the Population I delta Scuti variables whichoccupy adjacent regions of the instability strip.
| 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.
| Kinematics of metal-poor stars in the galaxy
We discuss the kinematic properties of a sample of 1936 Galactic stars,selected without kinematic bias, and with abundances (Fe/H) is less thanor equal to -0.6. The stars selected for this study all have measuredradial velocities, and the majority have abundances determined fromspectroscopic or narrow-/intermediate-band photometric techniques. Incontrast to previous examinations of the kinematics of the metal-poorstars in the Galaxy, our sample contains large numbers of stars that arelocated at distances in excess of 1 kpc from the Galactic plane. Thus, amuch clearer picture of the nature of the metal-deficient populations inthe Galaxy can now be drawn.
| Summary of Delta S metallicity measurements for bright RR Lyrae variables observed at Lick Observatory and KPNO between 1972 and 1987
From 1972 to 1987 we conducted a survey of the metallicity of faint RRLyrae variables in the Galactic halo, using the 'Butler system' of DeltaS. As part of the calibration of this program, we made approximately 500observations of bright RR Lyraes as abundance standards. We summarizeall the observations of these bright field RR Lyraes and provideaveraged values for the metallicity parameter Delta S. These averagesrepresent the most precise definition of the Butler system for themeasurement of RR Lyrae metallicities. The typical mean error is 0.3units in Delta S, which corresponds to 0.05 dex in (Fe/H). We alsobriefly discuss the weaknesses in the determination of (Fe/H) from DeltaS.
| AH Cam: A metal-rich RR Lyrae star with the shortest known Blazhko period
Analysis of 746 new V-band observations of the RR Lyrae star AH Camobtained during 1989 - 1992 clearly show that its light curve cannot bedescribed by a single period. In fact, at first glance, the Fourierspectrum of the photometry resembles that of a double-mode pulsator,with peaks at a fundamental period of 0.3686 d and an apparent secondaryperiod of 0.2628 d. Nevertheless, the dual-mode solution is a poor fitto the data. Rather, we believe that AH Cam is a single-mode RR Lyraestar undergoing the Blazhko effect: periodic modulation of the amplitudeand shape of its light curve. What was originally taken to be the periodof the second mode is instead the 1-cycle/d alias of a modulationsidelobe in the Fourier spectrum. The data are well described by amodulation period of just under 11 d, which is the shortest Blazhkoperiod reported to date in the literature and confirms the earliersuggestion by Goranskii. A low-resolution spectrum of AH Cam indicatesthat it is relatively metal rich, with delta-S less than or = 2. Itshigh metallicity and short modulation period may provide a critical testof at least one theory for the Blazhko effect. Moskalik's internalresonance model makes specific predictions of the growth rate of thefundamental model vs fundamental period. AH Cam falls outside the regimeof other known Blazhko variables and resonance model predictions, butthese are appropriate for metal-poor RR Lyrae stars. If the theorymatches the behavior of AH Cam for a metal-rich stellar model, thiswould bolster the resonance hypothesis.
| Infrared photometry and radial velocities of field RR Lyraes
Infrared photometry of 110 field RR Lyraes is presented along withradial velocities of 13 field RR Lyraes. The methods used are described.
| A re-analysis of the period shifts in RR Lyrae stars
The period shift in both field and globular cluster RR Lyrae stars isexamined. The stellar pulsation theory called the Sandage Period Shiftto determine the mean M(V) of RR Lyrae stars is investigated. Theadvantages of (V-K) compared to (B-V) as a temperature indicator for RRLyraes are discussed in detail. Period shift-metallicity relations arederived using recently published infrared photometry of field RR Lyraesand globular cluster RR Lyraes. Other method for determining mean M(V)for RR Lyraes are critically reviewed. It is argued that results formain sequence fitting, statistical parallax, and Red Giant Branch theoryare presently too uncertain to be used. The slope of themass-metallicity relation from pulsation theory is in seriousdisagreement with that from Horizontal Branch Theory.
| Detection of a galactic color gradient for blue horizontal-branch stars of the halo field and implications for the halo age and density distributions
Abstract image available at:http://adsabs.harvard.edu/abs/1991ApJ...375..121P
| Period analysis of the RR Lyrae star RU PISCIUM
RU Psc is a c-type RR Lyrae star (period P = 0.39 d) known for irregularcycle-to-cycle brightness variations and a possible 28 d Blazhko period.Using proven period-finding techniques over 1100 extant photometricobservations were analyzed to see if RU Psc might also be a double-modeRR Lyrae star of the kind recently discovered in the globular clusters M15, M 3, and IC 4499 (Cox et al. 1983; Clement et al. 1986), and in theDraco dwarf galaxy (Nemec 1985). It is concluded that the peculiaritiesseen in the photometry of RU Psc are due primarily to rapid andirregular period changes, and are not due to low-amplitude oscillationscaused by a secondary period.
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