An extensive photometric study of the Blazhko RR Lyrae star DM Cyg

Jurcsik, J.; Sódor, Á.; Hajdu, G.; Szeidl, B.; Dózsa, Á.; Posztobányi, K.; Smitola, P.; Belucz, B.; Fehér, Virág Piroska; Kővári, Zs.; Kriskovics, L.; Kun, Emma; Molnár, L.; Nagy, I.; Vida, K.; Görög, N.

doi:10.1111/j.1365-2966.2009.14919.x

Cited by 35 publications

(47 citation statements)

References 16 publications

(28 reference statements)

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“…The nonwhite distribution of the photometric residuals is the cause of the small bunches of frequencies observed in the residual spectrum. The Blazhko variables RR Gem and DM Cyg show the same light curve shape and the same residual distribution as CoRoT 101128793 (Jurcsik et al 2005(Jurcsik et al , 2009a.…”

Section: The Main F 0 Term and Its Harmonicsmentioning

confidence: 75%

“…The real mechanism must be able to reproduce both the regular structure of the sidepeaks in the frequency spectra and the observed variability on a long-term scale. In this context, it can be useful to stress that CoRoT 101128793, similar to DM Cyg (Jurcsik et al 2009a) 2 We note that there is a 1 d −1 spacing between the terms of the first couple and between those of the second one. This spacing is always a bit suspicious for observations collected mostly from one site, but we consider the frequency detection performed by Jurcsik et al (2008) as a well-established one.…”

Section: Discussionmentioning

confidence: 99%

“…The observation of Blazhko RR Lyrae stars was performed with remarkable success by means of extensive ground-based surveys. Well-defined findings (e.g., changes in the Blazhko period, modulation features, systematic changes in the global mean physical parameters, high-order multiplets, long-term changes) have recently been obtained on RR Lyr itself , MW Lyr (Jurcsik et al 2008), XZ Cyg (LaCluyzé et al 2004), RR Gem (Jurcsik et al 2005;Sódor et al 2007), and DM Cyg (Jurcsik et al 2009a).…”

Section: Introductionmentioning

confidence: 99%

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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 Main F 0 Term and Its Harmonicsmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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CoRoT light curves of RR Lyrae stars

Poretti¹,

Paparó

Deleuil

et al. 2010

A&A

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“…Extensive multicolor photometric observations of high modulation amplitude RRab Blazhko stars have been performed by Jurcsik et al (2009a) for MW Lyr, by Jurcsik et al (2009b) for DM Cyg, by Sodor (2009) for RR Gem and SS Cnc, by Jurcsik et al (2011a) for CZ Lac, by Jurcsik et al (2012) for RZ Lyr, and by Sodor et al (2012) for XY And and UZ Vir. The average effective temperature is derived from the mean light curves by an inverse photometric Baade-Wesselink method using static-atmosphere models (Sodor 2009).…”

Section: The Second Required Process: the Decrease Of The Average Effmentioning

confidence: 99%

Atmospheric dynamics in RR Lyrae stars

Gillet

2013

A&A

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Context. Discovered in 1907, the Blazhko effect is a modulation of the light variations of about half of the RR Lyr stars. It has remained unexplained for over 100 years, despite more than a dozen proposed explanations. Today it represents an ongoing challenge in variable-star research. Aims. We propose a new explanation. It is based on the observation that Blazhko stars seem to be located in the region of the instability strip where fundamental and first overtone modes are excited at the same time.Methods. An analysis of nonlinear and nonadiabatic pulsation models of RR Lyrae stars shows that a specific shock (called first overtone shock) may be generated by the perturbation of the fundamental mode by the transient first overtone. Results. The first overtone shock induces a sharp slowdown of the atmospheric layers during their infalling motion. This slowdown in turn affects the compression rate on the deep photospheric layers and the intensity of the κ-mechanism. After an amplification phase, the intensity of the main shock wave before the Blazhko maximum becomes high enough to provoke large radiative losses. These can be at least equal to 70% of the total energy flux of the shock, which induces a small decrease of the effective temperature at each pulsation cycle. In these conditions, when the intensity of the main shock reaches its highest critical value at the Blazhko maximum, it completely desynchronizes the motion of the phostospheric layers. At this point, the atmosphere relaxes and reaches a new synchronous state that occurs at the Blazhko minimum. Conclusions. The combined effects of these two shocks on the atmosphere cause the Blazhko effect. This effect can only exist if the first overtone mode is excited together with the fundamental mode. Because the involved physical mechanisms are essentially nonlinear (shocks, atmospheric dynamics, radiative losses, mode excitations), the Blazhko process is expected to be unstable and irregular. Consequently, the Blazhko process has a specific random nature that is in contrast with the pulsation of non-Blazhko stars.

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“…The appearance of the Blazhko modulation frequency f m itself was a long-standing debate. However, it has always been detected in the spectra of extended enough photometric data sets (Kovács 1995;Nagy 1998;Jurcsik et al 2005Jurcsik et al , 2006Jurcsik et al , 2008Jurcsik et al , 2009). In the case of MW Lyr it was found together with its first harmonics 2 f m .…”

Section: Frequency Analysismentioning

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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An extensive photometric study of the Blazhko RR Lyrae star DM Cyg

Cited by 35 publications

References 16 publications

CoRoT light curves of RR Lyrae stars

CoRoT light curves of RR Lyrae stars

Atmospheric dynamics in RR Lyrae stars

First CoRoT light curves of RR Lyrae stars

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