Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars

Szabo, Robert M.; Kollath, Zoltán; Molnár, L.; Kolenberg, K.; Kurtz, D. W.; Bryson, Steve; Benkő, J. M.; Christensen‐Dalsgaard, J.; Kjeldsen, H.; Borucki, W. J.; Koch, David; Twicken, Joseph D.; Chadid, M.; Criscienzo, M. Di; Jeon, Young‐Beom; Moskalik, P.; Nemec, J. M.; Nuspl, J.

doi:10.1111/j.1365-2966.2010.17386.x

Cited by 133 publications

(214 citation statements)

References 27 publications

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“…The frequencies located between the HIFs and 2f 0 harmonics belong to the second radial overtone (f 2 ), while peaks between f 0 and HIFs are identified as the frequency of the first radial overtone mode (f 1 ). The explanation of the huge number of surrounding peaks around all three cases is mathematical: the amplitude of the additional frequencies for both the PD effect and overtone modes changes in time (see, e.g., Benkő et al 2010;Szabó et al 2010Szabó et al , 2014Guggenberger et al 2012). Such a variable signal results in a forest of peaks in the Fourier spectra as it was shown by Szabó et al (2010).…”

Section: Fourier Analysis Of the Light Curvesmentioning

confidence: 99%

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

Benkő

Plachy

Szabo

et al. 2014

ApJS

Self Cite

163

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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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Section: Fourier Analysis Of the Light Curvesmentioning

confidence: 99%

“…The middle ones belong to the period doubling (PD) phenomenon Szabó et al 2010;Kolláth et al 2011). The half-integer frequencies (HIFs: 0.5f 0 , 1.5f 0 , .…”

Section: Fourier Analysis Of the Light Curvesmentioning

confidence: 99%

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

Benkő

Plachy

Szabo

et al. 2014

ApJS

Self Cite

163

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“…To reduce the number of false positives, i.e., periodic variability not related to stellar rotation, we discarded 17 eclipsing binaries 2 , 878 planetary candidates 3 , 2 RR Lyrae stars Szabó et al 2010;Benkő et al 2010;Guggenberger et al 2012;Nemec et al 2011Nemec et al , 2013Moskalik et al 2012;Molnár et al 2012), and 84 γ Doradus and δ Scuti stars Ulusoy et al 2014;Balona et al 2011;Uytterhoeven et al 2011;Lampens et al 2013;Balona 2014). In total, 981 stars were discarded, leaving 23 143 targets, which are analyzed as described in the following section.…”

Section: Kepler Datamentioning

confidence: 99%

Rotation, differential rotation, and gyrochronology of activeKeplerstars

Reinhold

Gizon

2015

A&A

180

170

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Context. In addition to the discovery of hundreds of exoplanets, the high-precision photometry from the CoRoT and Kepler satellites has led to measurements of surface rotation periods for tens of thousands of stars, which can potentially be used to infer stellar ages via gyrochronology. Aims. Our main goal is to derive ages of thousands of field stars using consistent rotation period measurements derived by different methods. Multiple rotation periods are interpreted as surface differential rotation (DR). We study the dependence of DR with rotation period and effective temperature. Methods. We reanalyze a previously studied sample of 24 124 Kepler stars using different approaches based on the Lomb-Scargle periodogram. Each quarter (Q1-Q14) is treated individually using a prewhitening approach. Additionally, the full time series and their different segments are analyzed. Results. For more than 18 500 stars our results are consistent with the rotation periods from McQuillan et al. (2014, ApJS, 211, 24). Of these, more than 12 300 stars show multiple significant peaks, which we interpret as DR. Dependencies of the DR with rotation period and effective temperature could be confirmed, e.g., the relative DR increases with rotation period. Gyrochronology ages between 100 Myr and 10 Gyr were derived for more than 17 000 stars using different gyrochronology relations, most of them with uncertainties dominated by period variations. We find a bimodal age distribution for T eff between 3200-4700 K. The derived ages reveal an empirical activity-age relation using photometric variability as stellar activity proxy. Additionally, we found 1079 stars with extremely stable (mostly short) periods. Half of these periods may be associated with rotation stabilized by non-eclipsing companions, the other half might be due to pulsations. Conclusions. The derived gyrochronology ages are well constrained since more than ∼93.0% of the stars seem to be younger than the Sun where calibration is most reliable. Explaining the bimodality in the age distribution is challenging, and limits accurate stellar age predictions. The relation between activity and age is interesting, and requires further investigation. The existence of cool stars with almost constant rotation period over more than three years of observation might be explained by synchronization with stellar companions, or a dynamo mechanism keeping the spot configurations extremely stable.

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“…Molnár et al in these proceedings). Besides the half-integer frequencies due to period-doubling [12], extra frequencies have been found around the expected location of the second radial overtone frequency [13], around P X /P 1 = 0.61 [14], where P 1 and P X are the periods of first radial overtone and a presumably nonradial mode which seems to be ubiquitous in RRc and RRd stars [15]. In addition, anomalous first overtone / fundamental mode (P 1 /P 0 ) period ratios were uncovered [16], [17], [18], [19].…”

Section: Preliminary Resultsmentioning

confidence: 99%

The K2 RR Lyrae Survey

et al. 2017

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Abstract. We have initiated a large survey with K2 to observe thousands of RR Lyrae stars along the Ecliptic. The high photometric precision and the 80-90-day continuous coverage will allow us to investigate the light variation of these galactic structure tracer variable stars with an unprecedented detail. The survey will help us to conduct a thorough statistical study of RR Lyrae pulsation dynamics including old and recently discovered dynamical phenomena, like resonances, non-radial modes, period doubling, and the Blazhko effect. We describe the survey, present the first results and discuss the prospects of combining the K2 RR Lyrae survey, Gaia, and LSST in the context of galactic structure studies.

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Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars

Cited by 133 publications

References 27 publications

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

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

Rotation, differential rotation, and gyrochronology of activeKeplerstars

The K2 RR Lyrae Survey

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