A targeted search for repeating fast radio bursts with the MWA

Abstract

We present a targeted search for low-frequency (144–215 MHz) FRB emission from five repeating FRBs using 23.3 hr of archival data taken with the Murchison Widefield Array (MWA) Voltage Capture System (VCS) between 2014 September and 2020 May. This is the first time that the MWA VCS has been used to search for FRB signals from known repeaters, which enables much more sensitive FRB searches than previously performed with the standard MWA correlator mode. We performed a standard single pulse search with a temporal and spectral resolution of 400 μs and 10 kHz, respectively, over a 100 pc cm−3 dispersion measure (DM) range centred at the known DM of each studied repeating FRB. No FRBs exceeding a 6σ threshold were detected. The fluence upper limits in the range of 32–1175 Jy ms and 36–488 Jy ms derived from 10 observations of FRB 20190711A and four observations of FRB 20201124A respectively, allow us to constrain the spectral indices of their bursts to ≳ −1 if these two repeaters were active during the MWA observations. If free-free absorption is responsible for our non-detection, we can constrain the size of the absorbing medium in terms of the electron temperature T to <1.00 × (T/104K)−1.35 pc, <0.92 × (T/104K)−1.35 pc and <[0.22–2.50] × (T/104K)−1.35 pc for FRB 20190117A, 20190711A, and 20201124A, respectively. However, given that the activities of these repeaters are not well characterised, our non-detections could also suggest they were inactive during the MWA observations.

A commensal Fast Radio Burst search pipeline for the Murchison Widefield Array

“…on the size of the absorbing region) demonstrating the potential applications of the low-frequency observations (including nondetections). More recently, Tian et al (2023b) used archival MWA high-time resolution data from the Voltage Capture System (VCS; Tremblay et al 2015) to look for pulses from a modest sample of FRBs (one ASKAP and four CHIME). Although they did not detect any pulses from these FRBs, similar targeted searches with the MWA and other low-frequency telescopes have significant potential to detect low-frequency pulses from repeating FRBs.…”

“…The MWA is particularly well suited to detect potential FRB-like counterparts of GW events as described in James et al (2019) and supported by the recent associations of the CHIME FRB 190425A with GW190425 (Moroianu et al 2023;Panther et al 2023). Furthermore, as described by Tian et al (2023a), the MWA is also in a perfect geographical location to maximise the chances of detecting FRB counterparts of GW events detected by the LIGO-Virgo-KAGRA (LVK; Abbott et al 2018).…”

MWA rapid follow-up of gravitational wave transients: Prospects for detecting prompt radio counterparts

“…In the case where a GW event is well localised (positional error region of a few square degrees or with an identified electromagnetic counterpart), we will perform coherent beamforming (potentially at several positions, e.g. Tian et al 2023) before conducting single pulse dedispersion searches. We can also perform offline correlation of the VCS data to create images over longer integrations to search for persistent pulsar emission or other predicted long-lived coherent radio emission (e.g.…”

Narrowly Banded Spectra with Peak Frequency around 1 GHz of FRB 20201124A: Implications for Energy Function and Radiation Physics

“…Thirty-three bursts were detected with the CHIME telescope at 400-800 MHz (Lanman et al 2022), and 48 bursts were detected with the uGMRT telescope at 550-750 MHz (Marthi et al 2022). No burst has been detected at frequencies below 0.4 GHz, despite efforts of observation with the Murchison Widefield Array (MWA) at 144-215 MHz (Tian et al 2023). Only one burst was observed at 2 GHz, but no burst was detected in the X band (8374-8502 MHz) by simultaneously monitoring with the 64 m radio dish of the Usuda Deep Center/JAXA (Ikebe et al 2023).…”