Long-period radio transients (LPTs) emit radio pulses similar to those of pulsars, but at much longer periods – on the order of minutes to hours. With duty cycles of only a few percent, individual pulses have been observed to last between 10 and 1000 seconds. This places LPTs in a timescale gap between the two main techniques used in transient radio searches: time-series analysis at millisecond to second timescales, and image-plane searches sensitive to variability on the scale of days. As a result, LPTs remained undetected until recently, and only a handful are currently known.

To increase the sample of known LPTs, Lee et al. conducted a dedicated search using 200 hours of archival ASKAP EMU data, covering 750 square degrees of sky at the shortest possible imaging time step of 10-seconds. This represents the first large-scale search using ASKAP data at second-scale resolution. Previous ASKAP radio star searches have primarily used VAST and RACS data, which have observation durations of only 12 and 15 minutes, respectively. Such short observation windows may have missed transients entirely or failed to capture their full duration, limiting the study of their variability.

The image above shows the EMU fields used in the study, along with the positions of known pulsars, magnetars, and LPTs. The blue patches indicate the EMU fields processed in this study, which have Galactic latitudes of less than 10 degrees. The background shows the Galactic emission at 887.5 MHz. Only white dwarf binaries with periodic radio emission are included in this plot. Although no LPTs were detected, the team identified flares from six stars, which will be highlighted in future ADAPs.