Orateur
Description
Blazars are among the most violent non-thermal sources in the universe, exhibiting dramatic variability across the electromagnetic spectrum. Yet, a fundamental question remains unanswered: how tightly coupled are their optical and gamma-ray emissions, and what does this tell us about the physical engines powering these objects? In this talk, I will present a multi-year study of optical and gamma-ray correlations in blazars using data from Fermi-LAT and the ZTF optical survey. By developing a similarity metric to quantify cross-band correlations and a robust flare detection algorithm, we find that ~20% of blazars in our sample show >3σ correlation hints with remarkably short or absent time lags, a possible evidence for co-spatial emission. Moreover, we examine the possibility of distinguishing between emission processes from the optical-gamma-ray correlation signature. We implement a real-time flare detection algorithm that achieves 72% purity in identifying gamma-ray flares and 98% in detecting optical low states, when compared with the gamma-ray high states detected following the former algorithm - demonstrating that optical surveys can serve as high-fidelity triggers for high-energy observations. This capability will be timely with the start of the Rubin Observatory, transmitting alerts through Fink. I will present the implementation of this methodology to detect and trigger observations on high or low blazar states in real time, providing a complement to the triggers from Fermi-LAT and, critically, enabling target-of-opportunity observations with the Cherenkov Telescope Array Observatory (CTAO).