# Statistical properties of the repeating fast radio burst source FRB 121102

## TL;DR

This paper investigates the statistical properties of the repeating fast radio burst source FRB 121102, revealing a bimodal distribution of waiting times and suggesting external mechanisms like collisions as the origin of its bursts.

## Contribution

It provides the first detailed analysis of waiting time distributions for FRB 121102, highlighting bimodal patterns and implications for burst generation mechanisms.

## Key findings

- Waiting times show a bimodal distribution with clusters at hundreds of seconds and 2-40 milliseconds.
- Waiting times are uncorrelated with burst intensity, indicating external origin mechanisms.
- External models, such as collisions between small bodies and neutron stars, are supported.

## Abstract

Currently, FRB 121102 is the only fast radio burst source that was observed to give out bursts repeatedly. It shows a high repeating rate, with more than one hundred bursts being spotted, but with no obvious periodicity in the activities. Thanks to its repetition, the source was well localized with a subarcsecond accuracy, leading to a redshift measurement of about 0.2. FRB 121102 is a unique source that can help us understand the enigmatic nature of fast radio bursts. In this study, we analyze the characteristics of the waiting times between bursts from FRB 121102. It is found that there is a clear bimodal distribution for the waiting times. While most waiting times cluster at several hundred seconds, a small portion of the waiting times are strikingly in the range of 2--40 millisecond. More interestingly, it is found that the waiting time does not correlate with the burst intensity, either for the preceding burst or for the subsequent burst. It strongly indicates that the repeating bursts should be generated by some external mechanisms, but not internal mechanisms. As a result, the models involving collisions between small bodies and neutron stars could be competitive mechanisms for this interesting source.