Quantifying the randomness and scale invariance of the repeating fast radio bursts

TL;DR

This study analyzes the statistical properties of repeating fast radio bursts (FRBs) from FAST observations, revealing non-random, scale-invariant features indicative of self-organized criticality.

Contribution

It introduces a comprehensive statistical analysis of energy and waiting time in repeating FRBs, demonstrating long-term memory and scale invariance in their activity.

Findings

Long-term memory in energy and waiting time series.

Deviation from complete randomness in burst activity.

Energy and waiting time fluctuations follow a $q$-Gaussian distribution.

Abstract

The statistical properties of energy and waiting time carry essential information about the source of repeating fast radio bursts (FRBs). In this paper, we investigate the randomness of energy and waiting time using four data samples from three extremely active repeating FRBs observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We report the deviation from complete randomness of the burst activity using three statistics, i.e., Hurst exponent, Pincus index and non-Gaussian probability density distribution of fluctuations. First, the Hurst exponent greater than 0.5 reveals that there is long-term memory in the time series of energy and waiting time. Second, the deviation of the Pincus index from 1.0 manifests that the time series is not completely random. Finally, the fluctuations of energy and waiting time follow the scale-invariant $q$-Gaussian distribution. All these statistical properties imply that, although the time series of repeating FRBs seems to be irregular, they are not completely random, similar to the features of self-organized criticality.