The Blazhko Effect of AR Herculis

Smith, Horace A.; Barnett, Michael; Silbermann, N. A.

doi:10.1086/300912

Cited by 26 publications

(23 citation statements)

References 12 publications

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“…This structure can be followed up to the third or fourth harmonic. We note in passing, that the observed frequency pattern is the same as found in several well-studied field RR Lyrae Blazhko variables (Borkowski 1980;Smith et al 1994Smith et al , 1999Kovács 1995;Nagy 1998;Szeidl & Kolláth 2000).…”

Section: Rr-bl Stars: Blazhko Variables With Three Symmetrically Spacsupporting

confidence: 84%

Fourier decomposition and frequency analysis of the pulsating stars with $P < $ 1 d in the OGLE database

Moskalik

Poretti

2003

A&A

101

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Abstract. We present the results of a systematic search for multiperiodic pulsators among the Galactic Bulge RR Lyrae stars of the OGLE-1 sample. We identify one "canonical" double-mode variable (RRd star) pulsating in two radial modes. In 38 stars we detect secondary periodicities very close to the primary pulsation frequency. This type of multiperiodic variables constitute ∼23% of RRab and ∼5% of RRc population of the Bulge. With the observed period ratios of 0.95−1.02 the secondary periods must correspond to nonradial modes of oscillation. Their beating with the primary (radial) pulsation leads to a long-term amplitude and phase modulation, known as the Blazhko effect. The Blazhko RRab variables occur more frequently in the Galactic Bulge than in the LMC. The opposite tendency is seen in case of the RRd stars. The differences of incidence rates are most likely caused by different metallicity of the two populations. We discuss pulsation properties of the OGLE-1 Blazhko stars and compare them with predictions of theoretical models. We argue, that the oblique magnetic pulsator model of Shibahashi (2000) cannot account for the observations and should be ruled out.

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Section: Rr-bl Stars: Blazhko Variables With Three Symmetrically Spacsupporting

confidence: 84%

Fourier decomposition and frequency analysis of the pulsating stars with $P < $ 1 d in the OGLE database

Moskalik

Poretti

2003

A&A

101

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“…4 the V light curve is folded according to this modulation period; sinusoidal variation in the height of maximum light is evident. The ephemerides of maximum pulsation light and maximum pulsation amplitude determined The currently viable theoretical explanations of the Blazhko phenomenon predict approximate equality of the amplitude ratios, and phase differences between the side lobe frequencies of the different order components in each colour (Kovács 1995;Shibahashi 2000;Smith et al 1999;Nowakowski & Dziembowski 2001). Although these predictions are based on simplified models it is worth checking the stability of these components in our data.…”

Section: Photometric Resultsmentioning

confidence: 99%

The Blazhko behaviour of RR Geminorum I

Jurcsik¹,

Sódor

Váradi

et al. 2005

A&A

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Abstract. Extended CCD monitoring of RR Gem revealed that it is a Blazhko type RRab star with the shortest Blazhko period (7.d 23) and smallest modulation amplitude (∆M max < 0.1 mag) currently known. The short period of the modulation cycle enabled us to obtain complete phase coverage of the pulsation at each phase of the modulation. This is the first multicolour observation of a Blazhko star which is extended enough to define accurate mean magnitudes and colours of the variable at different Blazhko phases. Small, but real, changes in the intensity mean colours at different Blazhko phases have been detected. The Fourier analysis of the light curves shows that, in spite of the mmag and smaller order of the amplitudes, the triplet structure is noticeable up to about the 14th harmonic. The modulation is concentrated to a very narrow, 0.2 phase range of the pulsation, centred on the supposed onset of the H emission during rising light. These observational results raise further complications for theoretical explanation of the long known but poorly understood Blazhko phenomenon.

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“…Quasi‐continuous, space‐based photometry allowed us to calculate the instantaneous periods for a few modulated stars: four CoRoT RR Lyrae stars revealed variations (Δ P / P total amplitudes) between 0.2 and 1.3 per cent (Szabó et al 2009) while V783 Cyg, observed with Kepler , showed a period change of ∼1.1 per cent (Kolenberg et al 2010b). We estimated period changes from published phase modulation plots and pulsation–modulation frequency values in Molnár & Kolláth (2010): four stars, SS Cnc (Jurcsik et al 2006), RR Lyr (Kolenberg et al 2006), AR Her (Smith et al 1999) and MW Lyr (Jurcsik et al 2008) have quite similar values to each other and to V783 Cyg, between 0.8 and 1.2 per cent, while for RR Gem (Jurcsik et al 2006) and DM Cyg (Jurcsik et al 2009a) it is somewhat lower, ∼0.3 per cent. To achieve such changes in the linear periods however, quite large variations are required in convective parameters.…”

Section: The Model and The Approachmentioning

confidence: 99%

Can turbulent convective variations drive the Blazhko cycle? Dynamical investigation of the Stothers idea

Molnár

Kollath

Szabo

2012

Monthly Notices of the Royal Astronomical Society

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The Blazhko phenomenon, the modulation of the pulsation of RR Lyrae stars, remains one of the most stubborn unsolved problems of stellar pulsation. The recent idea of Stothers proposes that periodic variations in the properties of the convective envelope may be behind the amplitude and phase modulation. In this work, we approximated the mechanism by introducing variations in the convective parameters of the Florida–Budapest hydrodynamic code and also by means of amplitude equations. We found that the process is only effective for long modulation periods, typically for more than 100 d, in agreement with the thermal time‐scales of the pulsation in RR Lyrae stars. Due to the slow response of the pulsation to the structure changes, short‐period, high‐amplitude Blazhko modulation cannot be reproduced with this mechanism or would require implausible variations in the convective parameters on short time‐scales. We also found that the modulation of the mixing length results in strong differences between both the luminosity and radius variations and the respective phase modulations of the two quantities, suggesting notable differences between the energy output of the photosphere and the mechanical variations of the layers. The findings suggest that the convective cycle model is not well suited as a stand‐alone mechanism behind the Blazhko effect.

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The Blazhko Effect of AR Herculis

Cited by 26 publications

References 12 publications

Fourier decomposition and frequency analysis of the pulsating stars with $P < $ 1 d in the OGLE database

Fourier decomposition and frequency analysis of the pulsating stars with $P < $ 1 d in the OGLE database

The Blazhko behaviour of RR Geminorum I

Can turbulent convective variations drive the Blazhko cycle? Dynamical investigation of the Stothers idea

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