The Large Array Survey Telescope (LAST) is a wide-field visual-band survey designed to explore the variable and transient sky with high cadence. Its raw data stream is automatically processed in near real time at the observatory site, producing science-quality images, catalogs, and transient alerts. Transient alerts are then reported to the Transient Name Server (TNS). The LAST pipeline comprises two major components: (i) processing and calibration of single images followed by the coaddition of 20 exposures, producing single-image and coadded-image catalogs; and (ii) the subtraction of coadded images from calibrated reference images followed by transient detection. In this work, we present a detailed description and validation of the second component of the pipeline. Transient detection is based on the algorithm for proper image subtraction (ZOGY). We combined ZOGY subtraction with the statistic for sub-pixel motion discrimination, together with a sequence of deterministic filtering steps, to produce a clean stream of transient candidates without the use of machine learning. Translient Using commissioning data, the pipeline achieves a preliminary 5σ limiting magnitude of 20.3–20.7,mag, a single-epoch transient detection efficiency of sim80%, and a purity of gtrsim90% at a signal-to-noise ratio of geq7.5σ.
Konno et al. (Fri,) studied this question.