Detection of 15 bursts from FRB 180916.J0158+65 with the uGMRT

TL;DR

This study used the upgraded GMRT to observe FRB 180916, detecting 15 bursts, analyzing their properties, and demonstrating the telescope's capability for precise localization and constraining potential radio counterparts.

Contribution

First uGMRT observations of FRB 180916 revealing burst variability, localization, and setting upper limits on persistent radio emission, showcasing its effectiveness for targeted FRB studies.

Findings

Detected 15 bursts with variable rates during active cycles

Achieved sub-arcsecond localization of some bursts

Set upper limits on persistent radio flux density at 650 MHz

Abstract

We report the findings of a uGMRT observing campaign on FRB 180916.J0158+65, discovered recently to show a 16.35-day periodicity of its active cycle. We observed the source at 550-750 MHz for $\sim 2$ hours each during three successive cycles at the peak of its expected active period. We find 0, 12, and 3 bursts respectively, implying a highly variable bursting rate even within the active phase. We consistently detect faint bursts with spectral energies only an order of magnitude higher than the Galactic burst source SGR~1935+2154. The times of arrival of the detected bursts rule out many possible aliased solutions, strengthening the findings of the 16.35-day periodicity. A short-timescale periodicity search returned no highly significant candidates. Two of the beamformer-detected bursts were bright enough to be clearly detected in the imaging data, achieving sub-arcsecond localization, and proving as a proof-of-concept for FRB imaging with the GMRT. We provide a $3\sigma$ upper limit of the persistent radio flux density at 650 MHz of $66~\mu{\rm Jy}$ which, combined with the EVN and VLA limits at 1.6~GHz, further constrains any potential radio counterpart. These results demonstrate the power of uGMRT for targeted observations to detect and localize known repeating FRBs.