Nonlinear beat Cepheid and RR Lyrae models

Kollath, Zoltán; Buchler, J. R.; Szabo, Robert M.; Csubry, Z.

doi:10.1051/0004-6361:20020182

Cited by 95 publications

(105 citation statements)

References 15 publications

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“…3, right panel in the bottom row). We obtained an independent confirmation of the Blazhko frequency from the magnitudes at the maximum brightness (see above) and from the application of the analytic signal method (Kolláth et al 2002). The magnitudes at maximum oscillate in a peak-to-peak interval of 0.06 mag (Fig.…”

Section: The Blazhko Frequency F Mmentioning

confidence: 79%

CoRoT light curves of RR Lyrae stars

Poretti¹,

Paparó

Deleuil

et al. 2010

A&A

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Context. The CoRoT (Convection, Rotation and planetary Transits) space mission provides a valuable opportunity to monitor stars with uninterrupted time sampling for up to 150 days at a time. The study of RR Lyrae stars, performed in the framework of the Additional Programmes belonging to the exoplanetary field, will particularly benefit from such dense, long-duration monitoring. Aims. The Blazhko effect in RR Lyrae stars is a long-standing, unsolved problem of stellar astrophysics. We used the CoRoT data of the new RR Lyrae variable CoRoT 101128793 ( f 0 = 2.119 d −1 , P = 0.4719296 d) to provide us with more detailed observational facts to understand the physical process behind the phenomenon. Methods. The CoRoT data were corrected for one jump and the long-term drift. We applied different period-finding techniques to the corrected timeseries to investigate amplitude and phase modulation. We detected 79 frequencies in the light curve of CoRoT 101128793. They have been identified as the main frequency f 0 and its harmonics, two independent terms, the terms related to the Blazhko frequency f m , and to several combination terms. Results. A Blazhko frequency f m = 0.056 d −1 and a triplet structure around the fundamental radial mode and harmonics were detected, as were a long-term variability on the Blazhko modulation. Indeed, the amplitude of the main oscillation is decreasing along the CoRoT survey. The Blazhko modulation is one of the smallest observed in RR Lyrae stars. Moreover, the additional modes f 1 = 3.630 and f 2 = 3.159 d −1 are detected. Taking its ratio with the fundamental radial mode into account, the term f 1 could be the identified as the second radial overtone. Detecting of these modes in horizontal branch stars is a new result obtained by CoRoT.

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Section: The Blazhko Frequency F Mmentioning

confidence: 79%

CoRoT light curves of RR Lyrae stars

Poretti¹,

Paparó

Deleuil

et al. 2010

A&A

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“…There are numerous opportunities for following frequency/ period variations from the traditional O − C diagram (Sterken 2005) to the analytic signal method (Kolláth et al 2002), or we can transform it to phase variation as, for example, N13. We have chosen here the O − C diagram analysis as a simple and clear method.…”

Section: Analysis Of the O − C Diagrammentioning

confidence: 99%

LONG-TIMESCALE BEHAVIOR OF THE BLAZHKO EFFECT FROM RECTIFIED KEPLER DATA

Benkő

Plachy

Szabo

et al. 2014

ApJS

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In order to benefit from the four year unprecedented precision of the Kepler data, we extracted light curves from the pixel photometric data of the Kepler space telescope for 15 Blazhko RR Lyrae stars. To collect all the flux from a given target as accurately as possible, we defined tailor-made apertures for each star and quarter. In some cases, the aperture finding process yielded sub-optimal results, because some flux have been lost even if the aperture contains all available pixels around the star. This fact stresses the importance of those methods that rely on the whole light curve instead of focusing on the extrema (O − C diagrams and other amplitude independent methods). We carried out detailed Fourier analysis of the light curves and the amplitude independent O − C diagram. We found 12 (80%) multiperiodically modulated stars in our sample. This ratio is much higher than previously found. Resonant coupling between radial modes, a recent theory for explaining the Blazhko effect, allows single, multiperiodic, or even chaotic modulations. Among the stars with two modulations, we found three stars (V355 Lyr, V366 Lyr, and V450 Lyr) where one of the periods dominates in amplitude modulation, but the other period has a larger frequency modulation amplitude. The ratio between the primary and secondary modulation periods is almost always very close to the ratios of small integer numbers. It may indicate the effect of undiscovered resonances. Furthermore, we detected the excitation of the second radial overtone mode f 2 for three stars where this feature was formerly unknown. Our data set comprises the longest continuous, most precise observations of Blazhko RR Lyrae stars ever published. These data are made publicly available and will be unrivaled for years to come.

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“…In this work we applied another approach, namely the analytical signal method (Kolláth et al 2002). It uses the mathematical theorem that connects the real and imaginary part of any complex function which is analytic in the upper half plane.…”

Section: Instantaneous Amplitude and Periodmentioning

confidence: 99%

First CoRoT light curves of RR Lyrae stars

Chadid¹,

Benkő

Szabo

et al. 2010

A&A

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Context. The CoRoT -Convection Rotation and planetary Transits -space mission is a great opportunity for monitoring stars with excellent time-sampling and unprecedented photometric precision for up to 150 days. As an important benefit, high-quality RR Lyrae light curves are obtained with a quasi-uninterrupted coverage over several pulsation and Blazhko cycles. Aims. The Blazhko effect in RR Lyrae stars is an unsolved problem of astrophysics. We used the high-precision space data to contribute more precise knowledge to explain the possible physical processes behind the phenomenon. Methods. We applied different period-finding techniques including Period04, MuFrAn, PDM and SigSpec. Amplitude and phase modulation were investigated by an analytical function method as well as with the traditional O-C diagrams. Results. The Blazhko modulation frequency is directly detected in the spectrum, as well as its first and second harmonics. It shows the non-linear nature of the Blazhko modulation. Besides the triplets, further higher-order modulation side peaks appear around the pulsation frequency as quintuplet, septuplet, nonuplet, undecaplet, tredecaplet, quindecaplet and sepdecaplet structures. Additional frequencies, not belonging to the classical multiplet structures, are detected, as well as their linear combinations with the fundamental radial mode. We interpret these additional terms as non-radial modes. During the five consecutive Blazhko cycles, there is a shift of the maximum phase around 0.011 pulsation phase which is likely the consequence of a long term modulation.

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Nonlinear beat Cepheid and RR Lyrae models

Cited by 95 publications

References 15 publications

CoRoT light curves of RR Lyrae stars

CoRoT light curves of RR Lyrae stars

LONG-TIMESCALE BEHAVIOR OF THE BLAZHKO EFFECT FROM RECTIFIED KEPLER DATA

First CoRoT light curves of RR Lyrae stars

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