Evidence for Gravitational Lensing in FRB 20190320B: A Potential Lens Mass of ∼420 Solar Masses

Abstract Due to their millisecond-duration pulses and high flux, fast radio bursts (FRBs) are ideal probes for detecting low-mass gravitational lensing signals, as their distinctive characteristics make them highly sensitive to subtle time delays and lensing effects. We search for lensing events using the high-time-resolution (2.56 μ s) channelized raw voltage (baseband) data of 58 FRBs consisting of at least two components publicly released by the Canadian Hydrogen Intensity Mapping Experiment/FRB Collaboration, which allows the microstructures of FRBs to be better resolved compared to the intensity data. We apply different algorithms to examine these FRBs and identify a lensing candidate, FRB 20190320B, with a delay of ∼1.24 ms and an intensity ratio of ∼1.16 between the two pulses. Although some methods show a significance exceeding 5 σ , we conservatively regard this event as a candidate due to the potential limitations of these methods. Assuming it is indeed a lensed signal, we estimate its redshifted lens mass to be ∼424 M ⊙ , which ranks among the lowest mass estimates reported for candidate lensed FRBs.