The detection of a new repeating fast radio burst and its localization to a dwarf galaxy is reported in Nature this week. Some features of this source of electromagnetic radiation are similar to the first repeating fast radio burst to be found, but it also stands out from other sources in terms of the suggested properties of the host environment. The discovery may have implications for the way in which fast radio bursts are used to study the Universe.
Fast radio bursts are pulses of radio-frequency electromagnetic radiation, first discovered in 2007. They are used to probe the content of the intergalactic medium (the space between galaxies). However, differences in observations of these bursts may affect their use as tools to study the intergalactic medium. In addition, it may also mean that distances inferred using the dispersion measure might not be accurate. For example, the extent to which host galaxies affect the dispersion of fast radio bursts (the dispersion measure) is generally thought to be small, but there has been at least one example where this does not appear to be the case.
The observations reported by Di Li and colleagues add to this exception to the rule. They describe a repeating fast radio burst, FRB 20190520B, and identify its host galaxy (J160204.31−111718.5). The galaxy is at a redshift of z = 0.241, which corresponds to a luminosity distance of 1,218 megaparsecs. FRB 20190520B is similar to the first-known repeating fast radio burst source, FRB 121102, in that it is hosted in a dwarf galaxy and has an associated compact, persistent radio source. However, the estimated dispersion measure of its host galaxy is nearly an order of magnitude higher than the average of fast radio burst host galaxies. The authors suggest that better characterization of host galaxy properties may improve our classification of fast radio bursts.
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