Speaker
Description
Over the past decade, our understanding of fast radio bursts (FRBs) has greatly increased. We have now discovered thousands of these millisecond-duration, extragalactic bursts, and have localised over a hundred of them to their host galaxies. While at least some FRBs appear to come from the ultra-magnetised neutron stars known as magnetars, the diverse locations and properties of FRBs suggest that this isn't the complete answer. Low-frequency detections of FRBs, below 300 MHz, have been elusive. To date, only two FRB sources have been detected at 150 MHz, both using LOFAR. Despite the challenges in finding them, low-frequency detections provide valuable insights about the FRB phenomenon because propagation effects are particularly pronounced at these frequencies. One LOFAR-detected FRB exhibits periodic activity, with the LOFAR bursts arriving later in the cycle. This source may be an interacting binary system. The other LOFAR-detected FRB is found in a low-density plasma environment that strongly contrasts with that seen from other repeating FRB sources. Is this FRB in a cleaner environment because it is older than others or because it has a different physical origin? In addition to explaining what we have learned from these two sources, I will summarise ongoing and upcoming efforts to detect FRBs using LOFAR. These include beam-formed searches through the LOTAAS survey, image-plane searches in the LoTSS survey, and dedicated follow-up beam-formed observations of known repeating FRBs. I will discuss how even in the absence of detections, low-frequency observations enable us to place valuable constraints on the burst rates and the local environments of these enigmatic sources. The repetition rate limits derived from these searches can guide future low-frequency follow-ups with instruments like LOFAR2.0, SKA-Low, and NenuFAR, paving the way for deeper insights into the nature of FRBs.
