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Known Galactic field Blazhko stars
A list of known Galactic field stars exhibiting Blazhko effectcontaining 242 stars is presented. All the entries including theirdesignations, positions, pulsation, and Blazhko periods were collectedfrom the available literature. The actual values of parameters aregiven.
| The All-sky GEOS RR Lyr Survey with the TAROT Telescopes: Analysis of the Blazhko Effect
We used the GEOS database to study the Blazhko effect of galactic RRabstars. The database is continuously enriched by maxima supplied byamateur astronomers and by a dedicated survey by means of the two TAROTrobotic telescopes. The same value of the Blazhko period is observed atdifferent values of the pulsation periods and different values of theBlazhko periods are observed at the same value of the pulsation period.There are clues suggesting that the Blazhko effect is changing from onecycle to the next. The secular changes in the pulsation and Blazhkoperiods of Z CVn are anticorrelated. The diagrams of magnitudes againstphases of the maxima clearly show that the light curves of Blazhkovariables can be explained as modulated signals, both in amplitude andin frequency. The closed curves describing the Blazhko cycles in suchdiagrams have different shapes, reflecting the phase shifts between theepochs of the brightest maximum and the maximum O - C. Our sampleshows that both clockwise and counterclockwise directions are possiblefor similar shapes. The improved observational knowledge of the Blazhkoeffect, in addition to some peculiarities of the light curves, has yetto be explained by a satisfactory physical mechanism.
| Can turbulent convective variations drive the Blazhko cycle? Dynamical investigation of the Stothers idea
The Blazhko phenomenon, the modulation of the pulsation of RR Lyraestars, remains one of the most stubborn unsolved problems of stellarpulsation. The recent idea of Stothers proposes that periodic variationsin the properties of the convective envelope may be behind the amplitudeand phase modulation. In this work, we approximated the mechanism byintroducing variations in the convective parameters of theFlorida-Budapest hydrodynamic code and also by means of amplitudeequations. We found that the process is only effective for longmodulation periods, typically for more than 100 d, in agreement with thethermal time-scales of the pulsation in RR Lyrae stars. Due to the slowresponse of the pulsation to the structure changes, short-period,high-amplitude Blazhko modulation cannot be reproduced with thismechanism or would require implausible variations in the convectiveparameters on short time-scales. We also found that the modulation ofthe mixing length results in strong differences between both theluminosity and radius variations and the respective phase modulations ofthe two quantities, suggesting notable differences between the energyoutput of the photosphere and the mechanical variations of the layers.The findings suggest that the convective cycle model is not well suitedas a stand-alone mechanism behind the Blazhko effect.
| Mid-infrared Period-luminosity Relations of RR Lyrae Stars Derived from the WISE Preliminary Data Release
Interstellar dust presents a significant challenge to extendingparallax-determined distances of optically observed pulsationalvariables to larger volumes. Distance ladder work at mid-infraredwavebands, where dust effects are negligible and metallicitycorrelations are minimized, has been largely focused on few-epochCepheid studies. Here we present the first determination of mid-infraredperiod-luminosity (PL) relations of RR Lyrae stars from phase-resolvedimaging using the preliminary data release of the Wide-field InfraredSurvey Explorer (WISE). We present a novel statistical framework topredict posterior distances of 76 well observed RR Lyrae that uses theoptically constructed prior distance moduli while simultaneouslyimposing a power-law PL relation to WISE-determined mean magnitudes. Wefind that the absolute magnitude in the bluest WISE filter is MW1 = (- 0.421 ± 0.014) - (1.681 ±0.147)log10(P/0.50118 day), with no evidence for acorrelation with metallicity. Combining the results from the threebluest WISE filters, we find that a typical star in our sample has adistance measurement uncertainty of 0.97% (statistical) plus 1.17%(systematic). We do not fundamentalize the periods of RRc stars toimprove their fit to the relations. Taking the Hipparcos-derived meanV-band magnitudes, we use the distance posteriors to determine a newoptical metallicity-luminosity relation. The results of this analysiswill soon be tested by Hubble Space Telescope parallax measurements and,eventually, with the GAIA astrometric mission.
| 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.
| Periodicity search as a tool for disentangling the contaminated colour light curve of CoRoT 102781750
Context. The CoRoT space mission (COnvection, ROtation and planetaryTransits) launched in December 2006, aims at finding transitingexoplanets and investigating stellar oscillation in adjacent stellarfields, called exo- and seismofields, respectively. Besides theseismofields, CoRoT has a strong potential for seismological research onthe exofields. Up to now, only a limited number of RR Lyrae stars havebeen classified among the CoRoT targets. Knowing the astrophysicalimportance of the RR Lyrae stars, we attempted to get useful informationeven from a contaminated light curve of a possible RR Lyrae pulsator. Aims: The star CoRoT 102781750 reveals a puzzle, showing a verycomplex and altering variation in different "CoRoT colours". Weestablished without doubt that more than a single star was situatedwithin the CoRoT mask. Using a search for periodicity as a tool, our aimis to disentangle the composite light curve and identify the type ofsources behind the variability. Methods: Both flux and magnitudelight curves were used. Conversion was applied after a jump- andtrend-filtering algorithm. We applied different types of period-findingtechniques including MuFrAn and Period04. Results: The amplitudeand phase peculiarities obtained from the independent analysis of CoRoTr, g, and b colours and ground-based follow-up photometric observationsruled out the possibility of either a background monoperiodic or aBlazhko type RR Lyrae star being in the mask. The main target, an activestar, shows at least two spotted areas that reveal a Prot =8.8 h (f0 = 2.735 c d-1) mean rotation period. Theevolution of the active regions helped to derive a period change ofdP/dt = 1.6 × 10-6 (18 s over the run) and adifferential rotation of ? = ??/? = 0.0074. The0.015m linear decrease and a local 0.005m increase in the dominantperiod's amplitude are interpreted as a decay of the old spotted regionand an appearance of a new one, respectively. A star that is detectedonly in the CoRoT b domain shows a f1 = 7.172 cd-1 pulsation connected to a 14.83d periodicity via anequidistant triplet structure. The best explanation for our observationis a ? Cep star with a corotating dust disk.The CoRoT space mission was developed and is operated by the Frenchspace agency CNES, with participation of ESA's RSSD and ScienceProgrammes, Austria, Belgium, Brazil, Germany, and Spain. Follow-upobservations were obtained at Piszkéstet?, the mountainstation of Konkoly Observatory.
| BAV-Results of observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
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| BAV-Results of Observations - Photoelectric minima of selected eclipsing binaries and maxima of pulsating stars.
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| Recent Maxima of 64 Short Period Pulsating Stars
This paper contains times of maxima for 64 short period pulsating stars(primarily RR Lyrae and d Scuti stars). This represents a portion of theCCD observations received by the AAVSO Short Period Pulsator (SPP)section through December 2009.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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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.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| BAV-Results of observations
This 62nd compilation contains the results of visual observations ofBAV-members from the years 2007 and 2008. Here we publish altogether 337minima and maxima of 201 eclipsing binaries, pulsating and eruptivestars. The data were acquired by 14 observers. The compilation containsalso one photographic- and two ccd-results.
| AR Her: phasenmodulation der lichtkurve.
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| BAV-Results observations.
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| 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 Extinction Toward the Galactic Bulge from RR Lyrae Stars
We present mean reddenings toward 3525 RR0 Lyrae stars from the Galacticbulge fields of the MACHO Survey. These reddenings are determined usingthe color at minimum V-band light of the RR0 Lyrae stars themselves andare found to be in general agreement with extinction estimates at thesame location obtained from other methods. Using 3256 stars located inthe Galactic Bulge, we derive the selective extinction coefficientRV,VR = AV/E(V - R) = 4.3 ± 0.2. This valueis what is expected for a standard extinction law with RV,BV= 3.1 ± 0.3.
| Die 22. Amateur-tagung der BAV fur beobachter veraenderlicher sterne.
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| AR Her: Periodenaenderung und Lichtkurve.
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| Korrekturen zu Vorhersagen im BAV Circular 2008.
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| Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
Context: The theory of stellar evolution can be more closely tested ifwe have the opportunity to measure new quantities. Nowadays,observations of galactic RR Lyr stars are available on a time baselineexceeding 100 years. Therefore, we can exploit the possibility ofinvestigating period changes, continuing the pioneering work started byV. P. Tsesevich in 1969. Aims: We collected the available times ofmaximum brightness of the galactic RR Lyr stars in the GEOS RR Lyrdatabase. Moreover, we also started new observational projects,including surveys with automated telescopes, to characterise the O-Cdiagrams better. Methods: The database we built has proved to be a verypowerful tool for tracing the period variations through the ages. Weanalyzed 123 stars showing a clear O-C pattern (constant, parabolic orerratic) by means of different least-squares methods. Results: Clearevidence of period increases or decreases at constant rates has beenfound, suggesting evolutionary effects. The median values are β =+0.14 d Myr-1 for the 27 stars showing a period increase andβ = -0.20 d Myr-1 for the 21 stars showing a perioddecrease. The large number of RR Lyr stars showing a period decrease(i.e., blueward evolution) is a new and intriguing result. There is anexcess of RR Lyr stars showing large, positive β values. Moreover,the observed β values are slightly larger than those predicted bytheoretical models.Tables 3, 4, 5 and Figs. 2, 3 are only available in electronic form athttp://www.aanda.org
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| The GEOS RR Lyr Survey
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| The Blazhko behaviour of RR Geminorum II. Long-term photometric results
Context: RR Gem is one of the few Blazhko RR Lyraethat has photometric observations available extended enough to study thelong-term courses of its pulsation and modulation properties in detail. Aims: We investigate the pulsation and modulation properties and therelations between them in RR Gem using photometricobservations from the past 70 years in order to gain further insightinto the nature of the Blazhko modulation. Methods: We studied thephotographic, photoelectric, and CCD light curves obtained at theKonkoly Observatory and other authors' published maxima observations.Detailed analysis of the light curves, maximum brightness, and O-C dataare carried out. Results: RR Gem showed modulationmost of the time it was observed. The modulation amplitude showed strongvariations from the undetectable level (less than 0.04 mag in maximumbrightness) to about 0.20 mag. The amplitudes of the amplitude and phasemodulations showed parallel changes, thus the total “power”of the modulation have changed during the past 70 years. Parallelchanges in the pulsation and modulation periods occur with adP_mod/dP_puls = 1.6 ± 0.8 × 103 ratio. We alsodetected 0.05-0.1 mag changes in the mean maximum brightness and meanpulsation amplitude.Tables 4-15 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/469/1033
| Equidistant frequency triplets in pulsating stars: the combination mode hypothesis
Context: .Multiplet structures are a common feature in pulsating stars,and can be the consequence of rotational splitting, mode interaction orsinusoidal amplitude variations. Aims: .In this paper we examinethe phenomenon of (nearly) equidistant triplets, which are unlikely tobe caused by rotational splitting, in different types of pulsatingstars: a δ Scuti variable (1 Mon), an RR Lyrae variable (RR Lyr)and a short-period Cepheid (V473 Lyr). We examine the hypothesis thatone of the modes forming the triplet results from a combination of theother two modes. Methods: .The analyses were carried out onrecent data sets by using multiple-frequency analyses and statisticswith the package PERIOD04. In particular, the small departures fromequidistance were calculated for the three selected stars.Results: .For the δ Scuti variable 1 Mon, the departure fromequidistance is only 0.000079 ± 0.000001 cd-1 (or 0.91± 0.01 nHz). For 1 Mon the Combination Mode Hypothesis with amode excited by resonance is the most probable explanation. For the starRR Lyr, the hypothesis of resonance through a combination of modesshould be considered. The results for the best-studied cepheid with aBlazhko period (V473 Lyr) are inconclusive because of an unfavorableperiod of 1.49d and insufficient data.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
We use data from the Northern Sky Variability Survey (NSVS), obtainedfrom the first-generation Robotic Optical Transient Search Experiment(ROTSE-I), to identify and study RR Lyrae variable stars in the solarneighborhood. We initially identified 1197 RRab (RR0) candidate starsbrighter than the ROTSE median magnitude V=14. Periods, amplitudes, andmean V magnitudes are determined for a subset of 1188 RRab stars withwell-defined light curves. Metallicities are determined for 589 stars bythe Fourier parameter method and by the relationship between period,amplitude, and [Fe/H]. We comment on the difficulties of clearlyclassifying RRc (RR1) variables in the NSVS data set. Distances to theRRab stars are calculated using an adopted luminosity-metallicityrelation with corrections for interstellar extinction. The 589 RRabstars in our final sample are used to study the properties of the RRabpopulation within 5 kpc of the Sun. The Bailey diagram of period versusamplitude shows that the largest component of this sample belongs toOosterhoff type I. Metal-rich ([Fe/H]>-1) RRab stars appear to beassociated with the Galactic disk. Our metal-rich RRab sample mayinclude a thin-disk, as well as a thick-disk population, although theuncertainties are too large to establish this. There is some evidenceamong the metal-rich RRab stars for a decline in scale height withincreasing [Fe/H], as was found by Layden. The distribution of RRabstars with -1<[Fe/H]<-1.25 indicates that within this metallicityrange the RRab stars are a mixture of stars belonging to halo and diskpopulations.
| 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.
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