A long period transient search method for the Murchison Widefield Array

Abstract We present an automated search method for radio transients on the minute timescale focused on the emerging long period transients (LPTs) in image-plane radio data. The method is tuned for use with the Murchison Widefield Array (MWA) and tested on archival observations from the GaLactic and Extragalactic All-Sky MWA Extended Survey (GLEAM-X) in the 70–300 MHz range. The images are formed from model-subtracted visibilities, before applying three filters to the time series of each pixel in an image, with each filter designed to be sensitive to a different transient behaviour. Due to the nature of radio interferometry and the refraction of the fluctuating ionosphere, the vast majority of candidates at this stage are artefacts which we identify and remove using a set of flagging measures. Of the 336 final candidates, 7 were genuine transients: 1 new LPT, 1 new pulsar, and 5 known pulsars. The performance of the method is analysed by injecting modelled transient pulses into a subset of the observations and applying the method to the result.