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Period and Amplitude Variability of the High-amplitude ? Scuti Star GP Andromedae
Extensive differential time-series CCD photometry has been carried outbetween 2003 and 2009 for the high-amplitude ? Scuti (HADS) starGP And. We acquired 12,583 new measurements consisting of 41 nights(153.3 hr) spanning over 2221 days. This is the largest time-series dataset to date for the star. Based upon these data and others available inthe literature, a comprehensive analysis has been conducted toinvestigate the pulsational properties of the star. Except for the knownfundamental period and its harmonics we failed to detect any additionalpulsation periods either radial or nonradial. We show clear amplitudevariability, but we failed to verify the previously claimed periodicamplitude modulation. Classic O-C analysis indicates that thefundamental pulsation period of GP And is slowly increasing at a rate of\dot{P}/P = (5.49\,+/-\, 0.1)\times 10^{-8} yr-1 inaccordance with the predictions of stellar evolutionary models. Findingsof nonradial oscillations in previously known radial high-amplitudepulsators are being increasingly reported. We have briefly reviewed thecurrent status of multiperiodicity and nonradial pulsation featuresamong the high-amplitude pulsators in the classic instability strip.
| 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.
| The CoRoT star 105288363: strong cycle-to-cycle changes of the Blazhko modulation
We present an analysis of the COnvection, ROtation and planetaryTransits (CoRoT) star 105288363, a new Blazhko RR Lyrae star of typeRRab (f0= 1.7623 d-1), observed with the CoRoTspacecraft during the second long run in the direction of the GalacticCentre (LRc02, time-base 145 d). The CoRoT data are characterized by anexcellent time-sampling and a low noise amplitude of 0.07 mmag in the2-12 d-1 range and allow us to study not only the finedetails of the variability of the star, but also long-term changes inthe pulsation behaviour and the stability of the Blazhko cycle. We use,among other methods, standard Fourier analysis techniques and O-Cdiagrams to investigate the pulsational behaviour of the Blazhko star105288363. In addition to the frequency pattern expected for a BlazhkoRR Lyrae star, we find an independent mode (f1= 2.984d-1) showing a f0/f1 ratio of 0.59which is similar to that observed in other Blazhko RR Lyrae stars. Thebump and hump phenomena are also analysed, with their variations overthe Blazhko cycle. We carefully investigated the strong cycle-to-cyclechanges in the Blazhko modulation (PB= 35.6 d), which seem tohappen independently and partly diametrically in the amplitude and phasemodulations. Furthermore, the phasing between the two types ofmodulations is found to change during the course of the observations.
| Long-term photometric monitoring of Messier 5 variables - II. Blazhko stars
The light curves of 50 RRab (RR0) stars in M5 collected in Szeidl et al.(Paper I) are investigated to detect Blazhko modulation. 18 Blazhkostars are identified, and modulation is suspected in two additionalcases. The mean pulsation period of Blazhko stars is 0.04 d shorter thanthe mean period of the entire RRab sample in M5. Among the RRab starswith period shorter than 0.55 d the incidence rate of the modulation isas high as 60 per cent. The mean B-V colours of Blazhko stars overlapwith the colours of first overtone RRc (RR1) pulsators. The mean Vmagnitudes of Blazhko stars are on the average 0.05-mag fainter thanthose of the RRab stars with stable light curves. Blazhko stars tend tobe situated close to the zero-age horizontal branch at the blue edge ofthe fundamental-mode instability strip in M5. We speculate that thisspecific location hints that the Blazhko effect may have an evolutionaryconnection with the mode switch from the fundamental to theovertone-mode pulsation.
| 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.
| Observational Evidence of Convective Cycles as the Cause of the Blazhko Effect in RR Lyrae Stars
Among RR Lyrae stars displaying the Blazhko effect, a few show no periodmodulation in spite of striking changes in their light amplitudes. Thisanomalous behavior and the mean period of the affected variables arepredicted correctly by the theory of slow convective cycles in thestellar envelope.
| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Stern der saison: RR Lyrae.
Not Available
| 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.
| First Quintuplet Frequency Solution of a Blazhko Variable: Light Curve Analysis of RV UMa
RV UMa is one of the RRab stars showing regular large-amplitudelight-curve modulation. Extended photoelectric observations of RV UMaobtained at the Konkoly Observatory were published by Kanyó, andthe data were analysed by Kovács. After detecting an error in thereduction procedure of the published Konkoly data, corrected photometricdata are presented with additional, previously unpublished measurements.The re-analysis of the combination of the corrected Konkoly datasupplemented by Preston & Spinrad's observations has led to thediscovery that the appropriate mathematical model of the light curve is,in fact, a quintuplet frequency solution, rather than, a triplet. Thisfinding has crucial importance in the interpretation of the Blazhkophenomenon, as a triplet (doublet) is the preferred structure inresonance models, quintuplet in magnetic models. Period changes of boththe pulsation and modulation light variations of RV UMa have beendetected based on its century-long photometric observations. An overallanticorrelation between the pulsation and modulation period changes canbe defined by dPBl /dP 0 = -8.6 ×104 gradient, i.e., the modulation period is longer if thepulsation period is shorter. Between 1946 and 1975 the pulsation andmodulation periods showed, however, parallel changes, which points tothe fact that there is no strict relation between the changes in theperiods of the pulsation and modulation.
| The BRITE satellite and Delta Scuti Stars: The Magnificent Seven
This paper examines the prospect of observing ? Scuti variableswith BRITE. In particular, some of the astrophysical questions, whichcan be investigated, are discussed together with the methods to beapplied. Finally, the seven bright stars suitable for BRITE arepresented.
| Korrekturen zu Vorhersagen im BAV Circular 2008.
Not Available
| 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
| The Blazhko behavior of RV UMa
RV UMa is one of the most extensively studied RR Lyrae stars showingBlazhko modulation. Its photometric observations cover more than 90years. The published photoelectric observations of RV UMa obtained atthe Konkoly Observatory (Kanyó 1976) were re-considered andcompleted with previously unpublished data. During the time interval ofthe observations the periods of both the pulsation and the modulationvaried within the ranges of 0.000007 and 0.9 days, respectively. We havefound a definite but not strict inverse relation between the pulsationand modulation periods of RV UMa.
| Studying Blazhko RR Lyrae stars with the 24-inch telescope of the Konkoly Observatory
About a dozen field RR Lyrae stars have been observed with the 24-inchHeyde-Zeiss telescope of the Konkoly Observatory at Svábhegy,Budapest, since its refurbishment in 2003. Most of the observing time isallocated for the investigation of the Blazhko modulation, a phenomenonthat still does not have a satisfactory explanation. The obtainedmulticolour CCD observations are unique in extent. The accuracy of themeasurements makes it possible to detect low amplitude modulation of thelight curve as well. The discovery of Blazhko stars with low modulationamplitudes warns that the incidence rate of the Blazhko modulation is,in fact, much larger than it was previously expected. This makes theefforts exploring the cause of the modulation even more important. Asummary of our measurements and results achieved during the last 3 yearsis presented.
| The GEOS RR Lyr Survey
Not Available
| 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
| The GEOS RR Lyr Survey
Not Available
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| The Blazhko effect of RR Lyrae in 2003-2004
Aims.Extensive photometry of RR Lyr was obtained over a 421-day intervalin 2003-2004, covering more than 10 Blazhko cycles in a multisitecampaign. The length and density of this data set allow for a detailedanalysis. Methods: .We used Fourier techniques to study RR Lyr'sbehavior over the pulsation and the Blazhko cycle. We propose atwo-frequency model for decomposing the frequency spectrum.Results: .The light variations were fitted with the main radialfrequency, its harmonics up to 11th order, and the detected tripletfrequencies. No significant quintuplet components were found in thefrequency spectrum. Given the total time span of the measurements, wecan now unambiguously conclude that the Blazhko period has becomenotably shorter than the previously known value of 40.8 days, whereasthe main pulsation period remained roughly the same. Changes in themodulation period have been reported for other well-studied Blazhkovariables. They challenge the explanations for the Blazhko effect whichlink the modulation period directly to the rotation period. The newphotometry reveals an interval in the pulsation cycle of RR Lyr duringwhich the star's intensity barely changes over the Blazhko cycle. Thisinterval occurs during the infalling motion and between the supposedphases of the early and the main shock. The data also permit a moredetailed study of the light curve shape at different phases in theBlazhko period through Fourier parameters.
| 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.
| The GEOS RR Lyr Survey
Not Available
| 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.
| Amplitude variability or close frequencies in pulsating stars - the δ Scuti star FG Vir
The nature of the observed amplitude variability of several modes in theδ Scuti star FG Vir is examined. This is made possible by theextensive photometry obtained during 2002-04, as well as the longphotometric time-base starting in 1992. In this star, three frequenciesshow strong amplitude and phase variations. In the power spectrum, thesefrequencies also show up as frequency doublets. However, since trueamplitude variability of a single frequency can also lead to (false)frequency doublets in the power spectrum, a specific test examining indetail the observed amplitude and the phase variations of an assumedsingle frequency is applied. For the frequencies at 12.15 and 23.40cycle d-1, it is shown that the amplitude variability of asingle mode can be ruled out. In particular, an important property ofbeating between two modes is fulfilled: the amplitude and the phase varysynchronously with a phase shift close to 90°. The origin of theamplitude variability of a third mode, namely, near 19.86 cycled-1, is not clear due to the long beat period of 20+ yr, forwhich the amplitude-phase test suffers from gaps in the coverage.However, even for this frequency, the amplitude variations can beexpressed well by a mathematical two-mode model.If we examine these three close frequency pairs together with other(usually more widely separated) close frequencies in FG Vir, 18 pairs offrequencies with separations closer than 0.10 cycle d-1 havebeen detected. It is shown that the majority of the pairs occur near thetheoretically expected frequencies of radial modes. Mode identificationsare available for only a few modes: the only detected radial mode at12.15 cycle d-1 is part of a close pair.It is shown that accidental agreements between the frequencies ofexcited modes can be ruled out because of the large number of detectedclose frequency doublets.
| The GEOS RR Lyr Survey
Not Available
| Blazhko effect and double-mode RR Lyrae stars .
There are two kinds of multi-periodic RR Lyrae stars. The Blazhko effectis a modulation of the primary light cycle that takes place on a typicaltimescale of tens of days. Double-mode RR Lyrae stars pulsatesimultaneously in the fundamental and first overtone radial modes. Thestate of our knowledge of these multi-periodic variables is reviewed.
| Close frequencies in pulsating stars: common and mysterious! .
Amplitude and phase variability are commonly found in many differenttypes of pulsating stars. This suggests a common, presently unknownphysical origin. We have examined the phenomenon in several delta Scutistars with extensive data and find the beating of close frequencies tobe responsible. This is demonstrated for the star FG Vir by testing therelationship between the observed amplitude and phase variations. Mostclose frequency pairs are situated near the observed or theoreticallypredicted frequencies of radial modes. The large number of detectedclose frequencies excludes the possibility of accidental frequencyagreements.
| Beobachtungskampagne SW Boo, was kam heraus?
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| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.
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| On the Distribution of the Modulation Amplitudes of Blazhko Type RRab Stars
Using all available data on the modulation properties of Blazhko RRabvariables connection has been found between the pulsation period and theamplitude of the modulation. The possible largest value of themodulation amplitude, defined as the sum of the Fourier amplitudes ofthe first four modulation frequency components, increases towardsshorter period variables.
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