SMMAN Studies of AGN Variability. I. Long-term Spectral Evolution and a Candidate ∼1000-day Quasi-periodic Modulation in 4C+72.28
Abstract
The SMMAN project has carried out nine years of radio flux monitoring in the C and K bands of the blazar 4C+72.28. The two bands show markedly different secular evolution, with a substantially stronger K-band decline producing a gradual decrease in the C-K spectral index. After accounting for this secular evolution, multiple timing diagnostics reveal a candidate quasi-periodic modulation with a characteristic timescale of ∼1000 d, most clearly in the C band. The C-band GLSP peak reaches a local significance of 3.29σ, while its global significance remains modest at ∼2σ and the monitoring baseline covers only about three cycles. Independent and joint MCMC fits support a phenomenological decomposition for both bands into a long-term linear trend and a recurrent component. Under the shared-period assumption, the joint fit returns a characteristic timescale of approximately 1027 d and a similar fractional recurrent amplitudes of ≃5.45%. Information-criterion comparisons favor the combined linear-plus-sinusoidal model in both bands. Cross-correlation analysis shows a nominal K-leading offset in the original light curves but a centroid consistent with zero lag after detrending, although the lag distributions overlap substantially. These results are consistent with a common recurrent modulation superposed on slower frequency-dependent jet evolution. Geometrical Doppler-factor modulation provides one plausible interpretation, although intrinsic and opacity-related processes cannot be excluded.
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BibTeX
@misc{wang2026smman,
title = {{SMMAN Studies of AGN Variability. I. Long-term Spectral Evolution and a Candidate $\sim1000$-day Quasi-periodic Modulation in 4C+72.28}},
author = {Xin Wang and Timur Mufakharov and Guiping Tan and Zhenhua Han and Ning Chang and Qi Yuan and Yunzhuo Wang and Xiang Liu and Lang Cui},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32168},
eprint = {2610.32168},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32168},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - SMMAN Studies of AGN Variability. I. Long-term Spectral Evolution and a Candidate ∼1000-day Quasi-periodic Modulation in 4C+72.28
AU - Xin Wang
AU - Timur Mufakharov
AU - Guiping Tan
AU - Zhenhua Han
AU - Ning Chang
AU - Qi Yuan
AU - Yunzhuo Wang
AU - Xiang Liu
AU - Lang Cui
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32168
UR - https://arxiv.org/abs/2610.32168
AB - The SMMAN project has carried out nine years of radio flux monitoring in the C and K bands of the blazar 4C+72.28. The two bands show markedly different secular evolution, with a substantially stronger K-band decline producing a gradual decrease in the C-K spectral index. After accounting for this secular evolution, multiple timing diagnostics reveal a candidate quasi-periodic modulation with a characteristic timescale of ∼1000 d, most clearly in the C band. The C-band GLSP peak reaches a local significance of 3.29σ, while its global significance remains modest at ∼2σ and the monitoring baseline covers only about three cycles. Independent and joint MCMC fits support a phenomenological decomposition for both bands into a long-term linear trend and a recurrent component. Under the shared-period assumption, the joint fit returns a characteristic timescale of approximately 1027 d and a similar fractional recurrent amplitudes of ≃5.45%. Information-criterion comparisons favor the combined linear-plus-sinusoidal model in both bands. Cross-correlation analysis shows a nominal K-leading offset in the original light curves but a centroid consistent with zero lag after detrending, although the lag distributions overlap substantially. These results are consistent with a common recurrent modulation superposed on slower frequency-dependent jet evolution. Geometrical Doppler-factor modulation provides one plausible interpretation, although intrinsic and opacity-related processes cannot be excluded.
ER -