An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solution

Abstract

We have obtained the most extensive and most accurate photometric data of a Blazhko variable MW Lyr during the 2006-2007 observing seasons. The data within each 0.05 phase bin of the modulation period (P_m=1/f_m) cover the entire light cycle of the primary pulsation period (P_0=1/f_0), making possible a very rigorous and complete analysis. The modulation period is found to be 16.5462 d, which is about half of that was reported earlier from visual observations. Previously unknown features of the modulation have been detected. Besides the main modulation frequency f_m, sidelobe modulation frequencies around the pulsation frequency and its harmonics appear at +/- 2 f_m, +/- 4 f_m, and +/- 12.5 f_m separations as well. Residual signals in the prewhitened light curve larger than the observational noise appear at the minimum-rising branch-maximum phase of the pulsation, which most probably arise from some stochastic/chaotic behaviour of the pulsation/modulation. The Fourier parameters of the mean light curve differ significantly from the averages of the Fourier parameters of the observed light curves in the different phases of the Blazhko cycle. Consequently, the mean light curve of MW Lyrae never matches its actual light variation. The Phi_21, Phi_31 phase differences in different phases of the modulation show unexpected stability during the Blazhko cycle. A new phenomenological description of the light curve variation is defined that separates the amplitude and phase (period) modulations utilising the phase coherency of the lower order Fourier phases.

Accepted for publication in MNRAS. 15 pages, 14 figures, and 7 printed tables (2 of them available in electronic form)

References in corpus (3)

• The shortest modulation period Blazhko RR Lyrae star: SS Cnc
• First quintuplet frequency solution of a Blazhko variable: light curve analysis of RV UMa
• Studying Blazhko RR Lyrae stars with the 24-inch telescope of the Konkoly Observatory

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• Known Galactic field Blazhko stars
• Variable turbulent convection as the cause of the Blazhko effect - testing the Stothers model
• Revisiting the Kepler non-Blazhko RR Lyrae sample: Cycle-to-cyle variations and additional modes
• Frequency analysis of the first-overtone RR Lyrae stars based on the Extended Aperture Photometry from the K2 data
• Intriguing triple-mode RR Lyrae star with period doubling
• On the connection between almost periodic functions and Blazhko light curves