Abstract
With the help of the Fourier transform, I verify that some stars classified as Blazhko variables are actually regularly pulsating RR Lyrae stars in binary systems.
Highlights
Introduction and summaryThe Blazhko phenomenon is the periodic variation in pulsation amplitude or phase seen in a large fraction of RR Lyrae stars ([1, 2]), and it still remains a long-lived enigma to be explained
The Fourier transform of eq (1) leads to ([7]) (i) multiplets with an equal spacing in frequency, equal to the orbital frequency, (ii) the amplitude ratio between the first sidelobe and the central component of each multiplet being proportional to the oscillation frequency, kν0, and (iii) the phase difference between the central component and the first sidelobes of each multiplet being π/2
The conspicious side peaks are caused by a year-gap of observations appearing in the window spectrum
Summary
The Blazhko phenomenon is the periodic variation in pulsation amplitude or phase (or equivalently, frequency) seen in a large fraction of RR Lyrae stars ([1, 2]), and it still remains a long-lived enigma to be explained. Phase modulation is seen in pulsating stars in binary systems, due to the light-travel time effect ([3, 4]). Some stars classified as Blazhko variables might be explained as binary systems. Hajdu et al ([5]) adopted the O-C method to detect binarity. Another way to discriminate these two causes more clearly is the Fourier transform ([6, 7]). By carefully investigating the multiplets seen in the Fourier spectra of RR Lyrae stars, I verify that some of the stars classified as Blazhko variables are non-Blazhko RR Lyrae stars in a binary system, and show that some stars classified as binary systems are not binaries
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