The detection of circularly polarized radio bursts from stellar and exoplanetary systems

In the Solar System, low-frequency radio emission at frequencies ≲200 MHz is produced by acceleration processes in the Sun and in planetary magnetospheres. Such emission has been actively searched for in other stellar systems, as it could potentially enable the study of the interactions between stars and the magnetospheres of their exoplanets. Here we present radio interferometric multiplexed spectroscopy (RIMS), a method designed to measure the variability of the flux density in an arbitrary number of directions from interferometric datasets. Using it, we synthesized ~200,000 dynamic spectra of stars and exoplanetary systems from an ~1.4 years’ long, multi-petabytes dataset from the Low-Frequency Array (LOFAR) at 150 MHz. This extra diagnostic shows that ~25% of the 68 targets previously identified in the LOFAR circularly polarized images also show significant variability on timescales of a few hours. The improved instantaneous sensitivity led to the detection of eight more weak bursts from low-mass stars, most of which varied on ~0.5–1-h timescales. We argue that some are fully compatible with radio emission generated by star–planet interactions, although an intrinsic stellar origin is still a possible explanation. Our results demonstrate the potential of the method for studying stellar and star–planet interactions with the Square Kilometre Array.