© JvL/KR

The ephemeral Fast Radio Bursts (FRBs) must be powered by some of the most energetic processes in the Universe. That makes them highly interesting in their own right, and as precise probes for estimating cosmological parameters. This field thus poses a unique challenge: FRBs must be detected promptly and immediately localised and studied based only on that single millisecond-duration flash. Recently we, Rajwade & van Leeuwen (2024), published a review on the search software pipelines used around to world to power these detections and studies -- including a number of techniques developed by astronomers at ASTRON.

In today's Daily Image, we show the various steps required in a FRB search and their impact on the time-frequency plane. Fiducial rates and parameter values are taken from the ALERT real-time survey that ARTS performed using Apertif/WSRT. Listed at the top for each step are the relevant data and compute and candidate rates. From left to right, data arrive from the telescope. These are cleaned from radio frequency interference (RFI). Of order 10^4 dispersion trials are next formed, and each is searched over ∼10 matched filters. The large number of candidates are next clustered and graded until about 10^3 remain, of which one is a new FRB. The FRB in this example was found (by Apertif) after 5% data loss to RFI, at a DM of 456 pc/cc and a downsampling factor of 4.

The search sequence produces and searches of order 10^12 realisations of the data for every FRB that is discovered. It is instructive to compare this stupendous number against the odds of finding the proverbial needle in the haystack. To match the effort required in a FRB search, the grassy pile would need to rival the Great Pyramid of Giza.