Autocorrelation signatures in time-resolved black hole flare images: Secondary peaks and convergence structure
Phys. Rev. D 112, 083024 – Published 14 October, 2025
DOI: https://doi.org/10.1103/zmnz-p2rs
Abstract
The strong gravitational field of a black hole bends light, forming multilevel images, yet extracting precise spacetime information from them remains challenging. In this study, we investigate how gravitational lensing leaves unique and detectable signatures in black hole movies using autocorrelation analysis. By examining the two-dimensional autocorrelation of a movie depicting a hot spot orbiting a Kerr black hole, as viewed by a near-axis observer, we identify a persistent secondary peak structure induced by gravitational lensing. Notably, these secondary peaks converge toward an approximately fixed point in the time-angle lag domain, largely independent of the orbital radius of the hot spot. This key property suggests that combining future flare observations with precise autocorrelation analysis could effectively disentangle lensing effects from orbital dynamics, enabling direct measurement of black hole parameters.
