Year: 2026
Type: article
Abstract: We present a frequency-domain and time-domain analysis of two rapidly modulated δ Scuti stars, KIC 10407873 and KIC 6963490, using long-cadence Kepler photometry. Fourier analysis reveals modulation-related side peaks in both targets. In KIC 6963490, the dominant frequency f 1 and its harmonic 2 f 1 are both split by the same modulation frequency, forming a coherent side-peak pattern that is difficult to explain as a chance alignment of independent close frequencies. To trace the modulation directly in the time domain, we apply complex demodulation to extract the instantaneous amplitude and phase of selected pulsation components. Both stars show coherent amplitude and phase variations, closed or nearly closed amplitude–phase loops, and rapid phase transitions near the amplitude minima. These features indicate that the phase modulation is closely associated with the amplitude modulation rather than varying independently. In addition, the synchronous harmonic splitting in KIC 6963490 further suggests that the modulation is coherently imprinted on the pulsation waveform. The similarity of these features to the amplitude–phase coupling and harmonic side-peak structures observed in Blazhko RR Lyrae stars suggests that rapidly modulated δ Scuti stars may involve an analogous modulation process, although its physical origin remains to be established. Our results also demonstrate that complex demodulation is an effective tool for resolving rapid pulsation modulation on timescales where conventional short-time Fourier analysis is limited.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: G4195113082, G7610025757
OpenAlex ID: W7214949315