A morphological search for stable year-scale modulation in gamma-ray blazars
This research developed a morphological framework to classify year-scale quasi-periodic oscillations (QPOs) in blazars using Singular Spectrum Analysis and Weighted Wavelet Z-transform. The framework categorizes sources into three ranks based on coherence and period stability, distinguishing between stable clock mechanisms (Rank I) and evolving or volatile modulations (Rank II). This helps identify physically distinct modulation behaviors.