Memory in the Burst Occurrence of Repeating FRBs

TL;DR

This paper uncovers a universal memory effect in the waiting times of repeating FRBs, showing that burst intervals depend on previous intervals and suggesting a common mechanism for repeating and non-repeating FRBs.

Contribution

It demonstrates for the first time that memory effects are present in the waiting time distribution of FRBs, providing a unified framework for understanding their occurrence.

Findings

Waiting times depend on previous intervals ($ $)

Short and long waiting times tend to cluster

Memory effects influence burst probability within time windows

Abstract

Understanding the nature of repeating fast radio bursts (FRBs) is crucial to probe their underlying physics. In this work, we analyze the waiting time statistics between bursts of three repeating FRBs from four datasets. We find a universally pronounced dependency of the waiting times on the previous time interval (denoted as $\lambda_0$). We observe a temporal clustering where short waiting times tend to be followed by short ones, and long by long comparative to their mean value. This memory dependency is manifested in the conditional mean waiting time as well as in the conditional mean residual time to the next burst, both of which increase in direct proportion to $\lambda_0$. Consequently, the likelihood of experiencing a subsequent FRB burst within a given time window after the preceding burst is generally influenced by the burst history. We reveal that for the first time, these memory effects are present in the scale-invariant preconditioned waiting time distribution. We show that the memory effect provides a unified description of waiting times which may account for both the repeating FRBs and the apparent non-repeating FRBs (i.e. only observed one time). These results shed new light on the mechanism of FRBs.