A plain-language summary of FRB 20250316A: A Brilliant and Nearby One-off Fast Radio Burst Localized to 13 pc Precision (CHIME/FRB Collaboration 2025, The Astrophysical Journal Letters; arXiv).
In one sentence: we traced an exceptionally bright, one-time radio flash to a spot just 42 light-years across inside a nearby galaxy, the sharpest view yet of where such a flash comes from.
Context
Most Fast Radio Bursts (FRBs) are flashes of radio light that happen so far away that they are detected only with the most sensitive radio telescopes. The burst in this study was also a typical FRB but it happened to occur in a galaxy that was super close to us; about 130 million light-years away, practically our backyard on cosmic scales. That made it the brightest FRB ever seen, and allowed us to study its immediate surroundings in unprecedented detail.
What did we do?
In March 2025, a Canadian radio telescope called CHIME caught an extremely bright burst, which the team nicknamed RBFLOAT (“radio brightest flash of all time”).
CHIME now has three smaller partner telescopes, in British Columbia, California and West Virginia. A burst reaches each site at a slightly different moment. Comparing those arrival times makes the four sites work like a single telescope the size of a continent, which can pin down positions very precisely. This was the first burst located with all of them working together.
Then other radio and optical telescopes looked at that spot. That included the Keck telescope in Hawaii, which we used to study the gas around the burst’s location.
My role here was to lead the study of the burst location using the Keck Cosmic Web Imager (KCWI), which essentially obtained a few thousand images of the location at different wavelengths of light. This allowed us to map the gas in the galaxy around the burst’s location and measure things like how many stars are forming there, what kind of stars are in the vicinity, how much “dust” is in that area, are there any “metals” (astronomer lingo for elements heavier than helium) and how fast the gas is moving. All of these inform us the kind of environment the burst was born in.
What did we find?
- The burst came from a galaxy 130 million light-years away. That is next door by the standards of these bursts.
- We know where it happened to within about 42 light-years. That is like picking out a single coin from 70 kilometres away.
- It sits near a region where stars are forming, but not inside it. It is about 600 light-years from the centre of the nearest one.
- There is no lingering radio glow at that spot. Some repeating bursts have one, and here we would have seen a glow 100 times fainter than any known.
- It has not repeated. For a source this close and this bright, we would have seen even much weaker repeat flashes, so it does not behave like any of the well-studied repeaters.
- The gas around the burst has a little less oxygen content than the Sun. This might have a bearing on what kind of stars might produce such bursts.
- It is just on the outskirts of a ragion in the galaxy which hosts a stellar nursery, i.e. an actively “star-forming region”.
Why does it matter?
The fact that CHIME was able to catch such a burst gives us hope that we should see such events once every few years. Amassing a sample of these nearby bursts might be the key to figuring out what makes them.
Words you’ll see in the paper
- One-off (or non-repeating) burst: a burst seen only once.
- VLBI: combining far-apart telescopes so that they act as one very large one.
- Outriggers: CHIME’s three partner telescopes.
- Persistent radio source: a steady radio glow at a burst’s location.
- Parsec (pc): a unit of distance, about 3.26 light-years.