FRBs

Fast radio bursts (FRBs) are extremely bright, millisecond-duration pulses of radio waves believed to originate outside the Milky Way. Their large dispersion measures indicate traversal through substantial ionized material, consistent with cosmological distances. The bursts are highly energetic, with luminosities that imply powerful engines, and some FRBs have been observed to repeat from the same location.

The first FRB was reported in 2007 (the Lorimer burst). Since then, hundreds have been found thanks to wide-field surveys, notably the CHIME telescope, which began routine FRB detection in 2018. A subset has been localized to host galaxies, enabling direct distance estimates and environmental studies.

Repeating FRBs have been identified, most famously FRB 121102, localized to a dwarf galaxy at redshift about 0.193 and associated with a persistent radio source. Another well-studied repeater, FRB 180916.J0158+65, lies in a nearby spiral galaxy and shows a periodic activity pattern. The existence of repeaters demonstrates that at least some FRB sources can emit multiple bursts from the same location, though many events have not yet been observed to repeat.

FRBs are detected over a wide range of radio frequencies, from hundreds of megahertz to a few gigahertz. Some FRBs exhibit polarization and large rotation measures, implying strong magnetic fields in dense, magnetized environments. Localizations to host galaxies enable studies of the intergalactic medium and halo gas along the line of sight.

The origin of FRBs remains uncertain. Leading models invoke magnetars—young, highly magnetized neutron stars—as a common source, but other possibilities include mergers of compact objects, accretion onto black holes, or exotic physics. It is possible that FRBs comprise multiple populations. Observational facilities such as Parkes, CHIME, ASKAP, and FAST continue to refine their properties and origins.