# Five new real-time detections of Fast Radio Bursts with UTMOST

## TL;DR

This paper reports the detection of five new fast radio bursts using the UTMOST telescope, with high time resolution studies revealing scattering effects and complex burst structures, and estimates the all-sky FRB rate at 843 MHz.

## Contribution

The study introduces a real-time FRB detection system at UTMOST enabling high-resolution analysis and provides the first all-sky FRB rate estimate at 843 MHz, suggesting a spectral turnover below 1 GHz.

## Key findings

- Five FRBs detected with high time resolution data.
- FRB181017 shows complex temporal structure with no lensing evidence.
- Estimated all-sky FRB rate at 843 MHz is 98^{+59}_{-39} events per day.

## Abstract

We detail a new fast radio burst (FRB) survey with the Molonglo Radio Telescope, in which six FRBs were detected between June 2017 and December 2018. By using a real-time FRB detection system, we captured raw voltages for five of the six events, which allowed for coherent dedispersion and very high time resolution (10.24 $\mu$s) studies of the bursts. Five of the FRBs show temporal broadening consistent with interstellar and/or intergalactic scattering, with scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows remarkable temporal structure, with 3 peaks each separated by 1 ms. We searched for phase-coherence between the leading and trailing peaks and found none, ruling out lensing scenarios. Based on this survey, we calculate an all-sky rate at 843 MHz of $98^{+59}_{-39}$ events sky$^{-1}$ day$^{-1}$ to a fluence limit of 8 Jy-ms: a factor of 7 below the rates estimated from the Parkes and ASKAP telescopes at 1.4 GHz assuming the ASKAP-derived spectral index $\alpha=-1.6$ ($F_{\nu}\propto\nu^{\alpha}$). Our results suggest that FRB spectra may turn over below 1 GHz. Optical, radio and X-ray followup has been made for most of the reported bursts, with no associated transients found. No repeat bursts were found in the survey.