Blazhko RR Lyrae light curves as modulated signals
We present an analytical formalism for the description of Blazhko RRLyrae light curves. In this formalism the amplitude and frequencymodulations are treated in a manner similar to the theory of electronicsignal transmission. We consider monoperiodic RR Lyrae light curves tobe carrier waves, and modulate their amplitude (AM), frequency (FM) andphase (PM); as a general case we discuss simultaneous AM and FM. Themain advantages of this method are the following: (i) the mathematicalformalism naturally explains numerous light-curve characteristics foundin the Blazhko RR Lyrae stars such as mean brightness variations,complicated envelope curves and non-sinusoidal frequency variations;(ii) our elucidation also explains the properties of the Fourier spectrasuch as apparent higher order multiplets, amplitude distribution of thesidepeaks, the appearance of the modulation frequency itself and itsharmonics. In addition, compared to the traditional methods, ourlight-curve solutions reduce the number of necessary parameters. Thisformalism can be applied to any type of modulated light curves, not justto Blazhko RR Lyrae star light curves.
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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.
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A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
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BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Automated Variable Star Classification Using the Northern Sky Variability Survey
We have identified 4659 variable objects in the Northern Sky VariabilitySurvey. We have classified each of these objects into one of the fivevariable star classes: (1) Algol/β Lyr systems includingsemidetached, and detached eclipsing binaries, (2) W Ursae Majorisovercontact and ellipsoidal variables, (3) long-period variables such asCepheid and Mira-type objects, (4) RR Lyr pulsating variables, and (5)short-period variables including δ Scuti stars. All the candidateshave outside of eclipse magnitudes of ~10-13. The primary classificationtool is the use of Fourier coefficients combined with period informationand light-curve properties to make the initial classification. Briefmanual inspection was done on all light curves to remove nonperiodicvariables that happened to slip through the process and to quantify anyerrors in the classification pipeline. We list the coordinates, period,Two Micron All Sky Survey colors, total amplitude variation, and anyprevious classification of the object. 548 objects previously identifiedas Algols in our previous paper are not included here.
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The unique frequency spectrum of the Blazhko RRc Star LS Her
The Blazhko effect in RR Lyrae stars is still poorly understoodtheoretically. Stars with multiple Blazhko periods or in which theBlazhko effect itself varies are particularly challenging. This studyinvestigates the Blazhko effect in the RRc star LS Her. Detailed CCDphotometry in the V, RC and IC band has beenperformed on 63 nights during six months. LS Her is confirmed to have aBlazhko period of 12.75 +/- 0.02 d. However, where normally the sidefrequencies of the Blazhko triplet are expected, an equidistant group ofthree frequencies is found on both sides of the main pulsationfrequency. As a consequence, the period and amplitude of the Blazhkoeffect itself vary in a cycle of 109 +/- 4 d. LS Her is a unique objectturning out to be very important in the verification of the theories forthe Blazhko effect.
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Multiperiodic Galactic field RR Lyrae stars in the ASAS catalogue
The All Sky Automated Survey (ASAS) monitors bright stars (8 < V <14 mag) south of declination +28°. The ASAS Catalogue of VariableStars (ACVS) presently contains 50099 objects; among them are 2212objects classified as RR Lyrae pulsating variables. We use ASASphotometric V-band data to search for multiperiodicity in those stars.We find that 73 of 1435 RRab stars and 49 of 756 RRc stars exhibit theBlazhko effect. We observe a deficiency of RRab Blazhko variables withmain pulsation periods greater than 0.65 d. The Blazhko periods of RRcstars exhibit a strongly bimodal distribution. During our study wediscovered the Blazhko effect with multiple periods in object ASAS050747-3351.9 = SU Col. Blazhko periods of 89.3 and 65.8 d and acandidate of 29.5 d were identified with periodogram peaks near thefirst three harmonics of the main pulsation. These observations mayinspire new models of the Blazhko effect, which has eluded a consistenttheory since its discovery about one hundred years ago. Long-term lightcurve changes were found in 29 stars. We also found 19 Galactic doublemode pulsators (RRd), of which four are new discoveries, raising thenumber of ASAS discoveries of such objects to 16, out of 27 known in thefield of our Galaxy.
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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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Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
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Photoelectric Maxima of Selected Pulsating Stars
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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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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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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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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Photoelectric Minima and Maxima of Selected Eclipsing and Pulsating Variables
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The Behlen Observatory variable star survey. Paper 3.
Finding charts, accurate coordinates and light curves are presented for146 variable stars including three which are newly discovered.Parameters descriptive of the light curves are tabulated includingperiods for eight stars which lacked them in the General Catalogue ofVariable Stars (the GCVS). GCVS periods of twelve stars were found to beseriously in error. The classification of the stars is discussed.Revisions or refinements of the classifications from the GeneralCatalogue of Variable of Stars are suggested for thirty-one stars. Ofthe nineteen stars classified as Bailey type c RR Lyrae stars in theGeneral Catalogue of Variable Stars, five are found to be short periodeclipsing or ellipsoidal variables. Seventeen percent of the Bailey typeab RR Lyrae stars and 14% of the type c's show scatter in their lightcurves which is suggestive of the Blazhko effect.
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CCD Observations of Short-Period Variables at Middlebury College
The Middlebury College Observatory is equipped with a 0.41-m reflectingtelescope and a CCD imaging camera. Among the observational programs wehave undertaken is the photometric study of short-period variable stars,especially delta Sct variables. There are many short-period (P < 6h)variables with amplitudes of several hundredths of a magnitude orgreater, which are ideal objects for study with CCDs on smalltelescopes, especially in educational settings.
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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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IAU Archives of Unpublished Observations of Variable Stars
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Osculating elements of 11 RR Lyrae-type stars.
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Strömgren four-colour observations of Northern Hemisphere binary systems
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Photoelectric observations of six eclipsing binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....6..131V&db_key=AST
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The light variations of XY Bootis and LS Herculis.
Abstract image available at:http://adsabs.harvard.edu/abs/1971AJ.....76..923B
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162 neue Veräderliche
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