SIMBAD references

Optical transient surveys continue to generate increasingly large data sets, prompting the introduction of machine-learning algorithms to search for quality transient candidates efficiently. Existing machine-learning infrastructure can be leveraged in novel ways to search these data sets for new classes of transients. We present a machine-learning accelerated search pipeline for the Deeper, Wider, Faster (DWF) programme designed to identify high-quality astrophysical transient candidates that contain a single detection. Given the rapid observing cadence of the DWF programme, these single-detection transient candidates have durations on sub-minute time-scales. This work marks the first time optical transients have been systematically explored on these time-scales, to a depth of m $\sim$ 23. We report the discovery of two high-quality sub-minute transient candidates from a pilot study of 671 761 light curves and investigate their potential origins with multiwavelength data. We discuss, in detail, possible non-astrophysical false positives, confidently reject electronic artefacts and asteroids, ruling out glints from satellites below 800 km and strongly disfavouring those at higher altitudes. We calculate a rate on the sky of $4.72^{+6.39}_{-3.28}\times 10^5$ per day for these sub-minute transient candidates.