Abstract
Abstract We present a simulation showing that super-Nyquist frequencies may have periodic amplitude and frequency modulations, even if actually stable, in time series sampled like the Kepler data. These modulations are caused by the barycentric time correction, which destroys the evenly spaced time measurements, making the Nyquist frequency variable over the spacecraft orbit around the Sun. These modulations can easily be identified in pulsating stars from Kepler's photometric data.
Highlights
Pulsating stars, exhibiting periodic luminosity variations, offer the unique opportunity to probe their interiors with the technique of asteroseismology
We report a simple simulation of stable signals beyond the Nyquist frequency that clearly show periodic amplitude and frequency modulations as a consequence of the frequency reflection relative to fNy
The simulations are performed with the following steps: (1) To reproduce Kepler’s sampling, we take the time array from one Kepler target with long cadence data from Quarter 1 to 17
Summary
Pulsating stars, exhibiting periodic luminosity variations, offer the unique opportunity to probe their interiors with the technique of asteroseismology. Using Fourier transforms, these photometric data are usually transposed into frequency space up to the Nyquist frequency fNy = 1/(2∆t), where the pulsation signals can be identified. Super-Nyquist frequencies can still be detected as a result of a reflection relative to the Nyquist frequency.
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