On Machine-learned Classification of Variable Stars with Sparse and Noisy Time-series Data
With the coming data deluge from synoptic surveys, there is a need forframeworks that can quickly and automatically produce calibratedclassification probabilities for newly observed variables based on smallnumbers of time-series measurements. In this paper, we introduce amethodology for variable-star classification, drawing from modernmachine-learning techniques. We describe how to homogenize theinformation gleaned from light curves by selection and computation ofreal-numbered metrics (features), detail methods to robustly estimateperiodic features, introduce tree-ensemble methods for accuratevariable-star classification, and show how to rigorously evaluate aclassifier using cross validation. On a 25-class data set of 1542well-studied variable stars, we achieve a 22.8% error rate using therandom forest (RF) classifier; this represents a 24% improvement overthe best previous classifier on these data. This methodology iseffective for identifying samples of specific science classes: forpulsational variables used in Milky Way tomography we obtain a discoveryefficiency of 98.2% and for eclipsing systems we find an efficiency of99.1%, both at 95% purity. The RF classifier is superior to othermethods in terms of accuracy, speed, and relative immunity to irrelevantfeatures; the RF can also be used to estimate the importance of eachfeature in classification. Additionally, we present the firstastronomical use of hierarchical classification methods to incorporate aknown class taxonomy in the classifier, which reduces the catastrophicerror rate from 8% to 7.8%. Excluding low-amplitude sources, the overallerror rate improves to 14%, with a catastrophic error rate of 3.5%.
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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.
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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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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
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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.
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The impact of HIPPARCOS on the RR Lyrae Distance Scale
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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
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Structural Properties of Pulsating Star Light Curves Through Fuzzy Divisive Hierarchical Clustering
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RR Lyrae Star Metallicities From Caby Photometry
Abstract image available at:http://adsabs.harvard.edu/abs/1996AJ....112.2132B
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The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
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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.
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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
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Quasi-160-minute oscillation period of Delta Scuti stars
The resonance power spectrum (or commensurability spectrum) computed for217 Delta Scuti stars indicates that the dominant (most commensurate)period for the total set of oscillation periods of these stars is 162.2+ or - 2.8 min. Within the error limits, this period coincidesapproximately with the 160-min period of global oscillations of the sun.
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Fourier decomposition of the light curves of high amplitude Delta Scuti and SX Phe stars
The light curves of monoperiodic, high amplitude ? Scuti and SXPhe stars have been Fourier decomposed in order to study theirstructural properties. The computed phase differences show a trend toincrease with the period similar to the trend observed in short periodCepheids and RR Lyrae stars. There is some evidence of a separation ofthe light curves in two groups, which indicates the presence of twotypes of pulsation. The proposed separation is discussed taking alsointo account the amplitude-amplitude diagrams, and some comparisons withRR Lyrae star light curves are made. For the present there are noevident physical differences between the stars in the two groups whichcan explain the separation.
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Revised list of pulsating stars with ultra-short periods
A comprehensive list of 178 known Delta Scuti and RR Lyrae-stars ispresented. Using this revised list a HR diagram for these ultra shortperiod pulsating stars is plotted and the blue and red edges of theresultant instability strip are determined. Selection effects arediscussed, and the PLC relationship of Breger (1979) is tested usingdata from this list. Stars lying outside the defined instability regionare discussed.
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IAU Archives of Unpublished Observations of Variable Stars
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The nature of dwarf Cepheids. V - Analysis and conclusions
The various observational arguments that can be or have been used todetermine the nature of dwarf Cepheids are examined. Three evolutionaryhypotheses are outlined and shown to lead to different expected periodchanges. Despite careful analysis, the derived period changes do notprovide definite information on the evolutionary stage of most of thestars examined. Evidence for the Population I nature of most dwarfCepheids (which are normal delta Scuti stars with large amplitudes) ispresented.
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The classification of intrinsic variables. VIII - Ultrashort period Cepheids
The photometric and astrometric data for ultrashort-period Cepheids withmaximum visual magnitudes brighter than 11.5 are collected anddiscussed. Most of these variables are high-mass, little-evolved starswhich, in the halo and disk populations, are blue stragglers. Theluminosities are calibrated from membership in disk and halo populationgroups; the visual magnitude equals 8(1-/c1/sub c) for disk stars, where(C1)sub c is a reddening- and temperature-free parameter.
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Intermediate Band and Hbeta Photometry of Ultrashort Period Cepheids
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Intermediate Band Photometry of BB Lyrae Stars. II. Colors of RR Lyrae and Ultra-Short Period Variables
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJS...25..487J&db_key=AST
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The short-period variable HDE 302013 = V753 CEN
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58th Name-List of Variable Stars
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HDE 302013 - a New Short-Period Variable Star
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INHABITED SKY
