Galactic radio transients (GRTs) are mysterious short-lived (∼days to months) radio transients that are quiet at all other wavelengths. Approximately half a dozen such sources have been reported to date, predominantly towards the Galactic center. However, no unifying properties have been identified among these, leaving their nature, emission mechanism, and even classification poorly understood. Due to the lack of periodic and uniform radio observations over wide areas of the Galactic plane until now, the sample size of such transients remained limited.

Anumarlapudi et al. we use radio observations from the ASKAP Variables and Slow Transients (VAST) survey to discover six new radio transients along the Galactic plane that resemble GRTs. Detailed investigation of archival data suggests that these sources may be divided into two classes: sources that exhibit sporadic, pulse-like (minutes) radio emission, and sources that exhibit long-term (weeks) flaring-type radio emission. For the short-time variable sources, the team draw similarities between optically bright long-period radio transients and their sample to propose wide-orbit (∼days) white dwarf binaries as underlying sources. For sources that show long-term outbursts, they draw comparisons between dust-obscured outbursts from white dwarf binaries and their sample. These results could imply that the ongoing wide-field radio surveys are uncovering radio emission from sub-populations of white dwarf binaries that were previously unexplored.

The figure above shows light curves of the candidate Galactic radio transients. Data shown as red stars are the measurements from the VAST Galactic survey, those shown as red downward pointing arrows are 5-σ upper limits from non-detections, and those shown in green and blue diamonds are the measurements from 8 hr target of opportunity ASKAP observations of different sources where our target source happened to be in the field. Shown in purple diamonds are the data from the Galactic Plane Monitor program of the Murchison Widefield Array (MWA), where open symbols are upper limits.