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Peer-reviewedCC BY 4.0The Astrophysical Journal

Complex Demodulation Reveals Blazhko-like Modulation Fingerprints in Delta Scuti Stars

  • Haozhi Wang1
  • Ali Esamdin2,3
  • Jianwei Yao2,3
  • Chenglong Lv2,4
  • Ayzada Jumahali2,3
  • Kedieryemu Kamili5
5 affiliations
  1. 1Chinese Academy of Sciences South America Center for Astronomy
  2. 2Chinese Academy of Sciences
  3. 3University of Chinese Academy of Sciences
  4. 4Instituto de Astrofísica de Andalucía—CSIC
  5. 5Xinjiang University
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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.

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Cite

BibTeXRIS
BibTeX
@article{wang2026complex,
  title = {{Complex Demodulation Reveals Blazhko-like Modulation Fingerprints in Delta Scuti Stars}},
  author = {Haozhi Wang and Ali Esamdin and Jianwei Yao and Chenglong Lv and Ayzada Jumahali and Kedieryemu Kamili},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = sep,
  doi = {10.3847/1538-4357/aea565},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea565},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Complex Demodulation Reveals Blazhko-like Modulation Fingerprints in Delta Scuti Stars
AU  - Haozhi Wang
AU  - Ali Esamdin
AU  - Jianwei Yao
AU  - Chenglong Lv
AU  - Ayzada Jumahali
AU  - Kedieryemu Kamili
PY  - 2026
DA  - 2026/09/30
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea565
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea565
AB  - 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.
SN  - 0004-637X
SN  - 1538-4357
ER  -