Fast Radio Bursts

Fast Radio Bursts (FRBs) are flashes of radio energy in the sky that last only a few thousandths of a second. They appear to originate from beyond the Milky Way Galaxy and, as such, contain prodigious amounts of energy. They were discovered in 2007 by astronomers using data gathered with the Parkes radio telescope in Australia.

Because they appear randomly over the sky and because of the relatively narrow field of view of most radio telescopes, only a couple of dozen have been observed since the initial discovery. The task of spotting them is akin to spotting fireflies in a dark forest while looking through a drinking straw.

Uncertainty remains regarding their source. The bursts could come from neutron stars as they collapse and become black holes; from evaporating black holes; from mergers of neutron stars; or from flares from stars with powerful magnetic fields called magnetars.

Recent U of T research provides evidence for one origin scenario: that FRBs could come from pulsars. If the signal from a pulsar passes through a cloud of gas, the gas may act like a magnifying glass, resulting in a brief and powerful burst of energy. Such a scenario could exist if the pulsar had a companion like a brown dwarf that was surrounded by a cloud of gas.

Virtually all known FRBs have been observed just once, making the phenomenon extremely difficult to study. An exception is the burst designated FRB 121102 which has repeated multiple times. Because it repeats, astronomers have been able to study it in greater detail and have traced its source to a star-forming region in a dwarf galaxy some three billion light-years away.

While much about their nature remains hidden, recent observations of FRB 121102 and others show that the signals have undergone Faraday Rotation, revealing that the signals passed through highly magnetized gas. Such cosmic environments exist in the immediate vicinity of supermassive black holes at the centres of galaxies. So, when we see an FRB, we may be seeing a signal from deep within the heart of a distant galaxy.

The quest to discover the true nature of FRBs continues on a number of fronts, including the Canadian Hydrogen Intensity Mapping Experiment (CHIME), an innovative radio telescope in B.C. that scans the entire northern sky once every day. Compared to a radio telescope that observes only a small patch of the sky at any time, CHIME is a powerful tool with which to discover the elusive and unpredictable FRBs.

At the Dunlap and U of T:

Recent Dunlap research:

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Artist impression of a Fast Radio Burst (FRB) reaching Earth. Three beams represent beams with different radio wavelengths which travel through interstellar plasma at different speeds. The resulting delay is called dispersion and is used to estimate the source’s distance. Image: Jingchuan Yu, Beijing Planetarium