An Unsupervised Search for Morphological Anomalies of Fast Radio Bursts From Tabulated Parameters of The Second CHIME/FRB Catalog

The second CHIME/FRB catalogue is the largest fast radio burst (FRB) sample released to date. Morphology is primarily used to characterise the population rather than to flag individ- ually atypical bursts. Understanding structure of single bursts could provide insight into the origin or mechanisms of FRBs. This work ran an unsupervised search over eight tabulated shape parameters. Six non-parametric detectors were used, chosen to span a range of anomaly types. Sensitivity was quantified by injecting synthetic anomalies over a range of strengths; specificity testing rejected indiscriminate detectors. The result is a shortlist of 36 morphologically atyp- ical candidates, annotated with the driving parameter and fit reliability. The majority of the shortlist is driven by parameters dependent on instrumental bias. The shortlist stands as a set of bursts whose dynamic spectra warrant direct examination.