Self-organized critical characteristics of teraelectronvolt photons from GRB 221009A

Abstract

The very high-energy afterglow in GRB 221009A, known as the “brightest of all time” (BOAT), has been thoroughly analyzed in previous studies. In this paper, we conducted a statistical analysis of the waiting time behavior of 172 TeV photons from the BOAT observed by LHAASO-KM2A. The following results were obtained: (I) The waiting time distribution (WTD) of these photons deviates from the exponential distribution. (II) The behavior of these photons exhibits characteristics resembling those of a self-organized critical system, such as a power-law distribution and scale-invariance features in the WTD. The power-law distribution of waiting times is consistent with the prediction of a nonstationary process. (III) The relationship between the power-law slopes of the WTD and the scale-invariant characteristics of the Tsallis q-Gaussian distribution deviates from existing theory. We suggest that this deviation is due to the photons not being completely independent of each other. In summary, the power-law and scale-free characteristics observed in these photons imply a self-organized critical process in the generation of teraelectronvolt photons from GRB 221009A. Based on other relevant research, we propose that the involvement of a partially magnetically dominated component and the continuous energy injection from the central engine can lead to deviations in the generation of teraelectronvolt afterglow from the simple external shock-dominated process, thereby exhibiting the self-organized critical characteristics mentioned above.