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Lorimer Burst – Observation of the first detected fast radio burst as described by Lorimer in 2006.[1]

In radio astronomy, a fast radio burst (FRB) is a transient radio wave of length ranging from a fraction of a millisecond, for an ultra-fast radio burst,[2][3] to 3 seconds,[4] caused by a high-energy astrophysical process that is not yet understood. Astronomers estimate the average FRB releases as much energy in a millisecond as the Sun puts out in three days.[5] While extremely energetic at their source, the strength of the signal reaching Earth has been described as 1,000 times less than from a mobile phone on the Moon.[6]

The first FRB was discovered by Duncan Lorimer and his student David Narkevic in 2007 when they were looking through archival pulsar survey data, and it is therefore commonly referred to as the Lorimer burst.[1][7] Many FRBs have since been recorded, including several that have been detected repeating in seemingly irregular ways.[8][9][10][11][12] Only one FRB has been detected to repeat in a regular way: FRB 180916 seems to pulse every 16.35 days.[13][14]

Most FRBs are extragalactic, but the first Milky Way FRB was detected by the CHIME radio telescope in April 2020.[15] In June 2021, astronomers reported over 500 FRBs from outer space detected in one year.[16]

When FRBs are polarized, it indicates that they are emitted from a source contained within an extremely powerful magnetic field.[17] The exact origin and cause of FRBs is still the subject of investigation; proposals for their origin range from a rapidly rotating neutron star and a black hole, to extraterrestrial intelligence.[18][19] In 2020, astronomers reported narrowing down a source of fast radio bursts, which may now plausibly include "compact-object mergers and magnetars arising from normal core collapse supernovae".[20][21][22] A neutron star has been proposed as the origin of an unusual FRB with periodic peaks lasting over 3 seconds reported in 2022.[23]

The discovery in 2012 of the first repeating source, FRB 121102, and its localization and characterization in 2017, has improved the understanding of the source class. FRB 121102 is identified with a galaxy at a distance of approximately three billion light-years and is embedded in an extreme environment.[24][17] The first host galaxy identified for a non-repeating burst, FRB 180924, was identified in 2019 and is a much larger and more ordinary galaxy, nearly the size of the Milky Way. In August 2019, astronomers reported the detection of eight more repeating FRB signals.[25][26] In January 2020, astronomers reported the precise location of a second repeating burst, FRB 180916.[27][28] One FRB seems to have been in the same location as a known gamma-ray burst.[29][15]

On 28 April 2020, a pair of millisecond-timescale bursts (FRB 200428) consistent with observed fast radio bursts, with a fluence of >1.5 million Jy ms, was detected from the same area of sky as the magnetar SGR 1935+2154.[30][31] Although it was thousands of times less intrinsically bright than previously observed fast radio bursts, its comparative proximity rendered it the most powerful fast radio burst yet observed, reaching a peak flux of either a few thousand or several hundred thousand janskys, comparable to the brightness of the radio sources Cassiopeia A and Cygnus A at the same frequencies. This established magnetars as, at least, one ultimate source of fast radio bursts,[32][33][34] although the exact cause remains unknown.[35][36][37] Further studies support the notion that magnetars may be closely associated with FRBs.[38][39] On 13 October 2021, astronomers reported the detection of hundreds of FRBs from a single system.[40][41]

In 2024, an international team led by astrophysicists of INAF, using detections from VLA, NOEMA interferometer, and Gran Telescopio Canarias has conducted a research campaign about FRB20201124A, one of the two known persistent FRB, located about 1.3 billion light-years away. Based on the outcomes of the study, authors deem to confirm the origin of FRBs in a binary system at high accretion rate, that would blow a plasma bubble, responsible for the persistent radio emission. The emission object, i.e. the "bubble", would be immersed in a star-forming region.[42]

Detection

[edit]
FRBs observed by CHIME in Galactic coordinates with locations of 474 nonrepeating and 18 repeating (62 bursts) sources from 28 August 2018 to 1 July 2019[43]

The first fast radio burst to be described, the Lorimer Burst FRB 010724, was found in 2007 in archived data recorded by the Parkes Observatory on 24 July 2001. Since then, many FRBs have been found in previously recorded data. On 19 January 2015, astronomers at Australia's national science agency (CSIRO) reported that a fast radio burst had been observed for the first time live, by the Parkes Observatory.[44] Many FRBs have been detected in real time by the CHIME radio telescope since it became operational in 2018, including the first FRB detected from within the Milky Way in April 2020.[33][45]

In January 2025, astronomers discovered radio waves from a galaxy that is roughly 2-billion light years away from Earth and is believed to be more than 11 billion years old.[46] These FRBs are associated with a galaxy that was believed to be dead.

Features

[edit]

Fast radio bursts are bright, unresolved (pointsource-like), broadband (spanning a large range of radio frequencies), millisecond flashes found in parts of the sky. Unlike many radio sources, the signal from a burst is detected in a short period of time with enough strength to stand out from the noise floor. The burst usually appears as a single spike of energy without any change in its strength over time. The bursts last for several milliseconds (thousandths of a second). The bursts come from all over the sky, and are not concentrated on the plane of the Milky Way. Known FRB locations are biased by the parts of the sky that the observatories can image.

Many have radio frequencies detected around 1400 MHz; a few have been detected at lower frequencies in the range of 400–800 MHz.[47] The component frequencies of each burst are delayed by different amounts of time depending on the wavelength. This delay is described by a value referred to as a dispersion measure (DM).[1] This results in a received signal that sweeps rapidly down in frequency, as longer wavelengths are delayed more.

The bursts are catalogued as FRB 190714, at top left; FRB 191001, at top right; FRB 180924, at bottom left; and FRB 190608, at bottom right.[48]

Extragalactic origin

[edit]

The interferometer UTMOST has put a lower limit of 10,000 kilometers for the distance to the FRBs it has detected, supporting the case for an astronomical, rather than terrestrial, origin (because signal sources on Earth are ruled out as being closer than this limit). This limit can be determined from the fact that closer sources would have a curved wave front that could be detected by the multiple antennas of the interferometer.[49]

Fast radio bursts have pulse dispersion measurements > 100 pc cm−3[50], much larger than expected for a source inside the Milky Way galaxy[51] and consistent with propagation through an ionized plasma.[1] Furthermore, their distribution is isotropic (not especially coming from the galactic plane);[49]: fig 3  consequently they are conjectured to be of extragalactic origin.

Origin hypotheses

[edit]

Because of the isolated nature of the observed phenomenon, the nature of the source remains speculative. As of 2022, there is no generally accepted single explanation, although a magnetar has been identified as a possible source. The sources are thought to be a few hundred kilometers or less in size, as the bursts last for only a few milliseconds. Causation is limited by the speed of light, about 300 km per millisecond, so if the sources were larger than about 1000 km, a complex synchronization mechanism would be required for the bursts to be so short. If the bursts come from cosmological distances, their sources must be very energetic.[6] Extending the technique of measuring pulsar emission region sizes using a scattering screen in the Milky Way, a method to estimate the transverse FRB emission region size using a scattering screen in the host galaxy was formulated in 2024.[52] Within the same year, a previously recorded burst, FRB 202210122A, was constrained to have an emission region size less than 30,000 km, using this technique.[53]

One possible explanation would be a collision between very dense objects like merging black holes or neutron stars.[54][55][56] It has been suggested that there is a connection to gamma-ray bursts.[57][58] Some have speculated that these signals might be artificial in origin, that they may be signs of extraterrestrial intelligence,[59][60][61] demonstrating veritable technosignatures.[62] Analogously, when the first pulsar was discovered, it was thought that the fast, regular pulses could possibly originate from a distant civilization, and the source nicknamed "LGM-1" (for "little green men").[63] In 2007, just after the publication of the e-print with the first discovery, it was proposed that fast radio bursts could be related to hyperflares of magnetars.[64][65] In 2015 three studies supported the magnetar hypothesis.[51][66][67][68] The identification of first FRB from the Milky Way, which originated from the magnetar SGR 1935+2154, indicates that magnetars may be one source of FRB.[33]

Especially energetic supernovae could be the source of these bursts.[69] Blitzars were proposed in 2013 as an explanation.[6] In 2014 it was suggested that following dark matter-induced collapse of pulsars,[70] the resulting expulsion of the pulsar magnetospheres could be the source of fast radio bursts.[71] In 2015 it was suggested that FRBs are caused by explosive decays of axion miniclusters.[72] Another exotic possible source are cosmic strings that produced these bursts as they interacted with the plasma that permeated the early Universe.[69] In 2016 the collapse of the magnetospheres of Kerr–Newman black holes were proposed to explain the origin of the FRBs' "afterglow" and the weak gamma-ray transient 0.4 s after GW 150914.[73][74] It has also been proposed that if fast radio bursts originate in black hole explosions, FRBs would be the first detection of quantum gravity effects.[56][75] In early 2017, it was proposed that the strong magnetic field near a supermassive black hole could destabilize the current sheets within a pulsar's magnetosphere, releasing trapped energy to power the FRBs.[76]

Plasma processes

[edit]

A variety of plasma-based mechanisms have been proposed to explain the coherent radio emission observed in FRBs. These processes typically involve relativistic magnetized plasmas, such as those found near magnetars or in shocks, where collective plasma effects and radiative processes can lead to the generation of bright, short-duration radio pulses. One promising mechanism is coherent electromagnetic emission from relativistic magnetized shocks, where the shock propagates in an electron–positron plasma with high magnetization (σ ≳ 1). These shocks generate X-mode polarized precursor waves through a synchrotron maser–like instability, with efficiencies and spectral features determined self-consistently via particle-in-cell simulations.[77][78] The shocks can arise from magnetar flares driving relativistic outflows, and may convert a small fraction of their energy (~10-3 σ-1) into coherent radio emission, consistent with observed FRB energetics. Another proposed mechanism is the electron cyclotron maser instability (ECMI), which can be triggered when synchrotron cooling generates ring-shaped momentum distributions that are unstable to X-mode wave growth.[79] This has been demonstrated in simulations of strongly magnetized plasmas where radiative losses sustain the coherent radio emission.[80]

Alternative models invoke coherent curvature radiation by bunched charges moving along curved magnetic field lines, often associated with magnetic reconnection near the surface or in the current sheet of neutron stars. In some versions, particle bunching is induced by plasma instabilities or perturbations in the magnetosphere.[81] Other proposals include antenna-type mechanisms, where coherent structures in the plasma (such as charge-separated bunches or solitons) radiate collectively,[82] and free electron laser (FEL)-like processes driven by reconnection-generated particle beams in magnetized turbulence.[83] In these models, particles interact with Alfvénic or electromagnetic wigglers and emit coherently via nonlinear Thomson or Compton-like scattering. Collectively, these plasma-based mechanisms aim to explain the high brightness temperatures, narrow-band spectra, and polarization features of FRBs, and are often framed within the magnetar scenario, although they may operate in broader astrophysical settings.

Hypotheses for repeating FRBs

[edit]

Repeated bursts of FRB 121102 have initiated multiple origin hypotheses.[84] A coherent emission phenomenon known as superradiance, which involves large-scale entangled quantum mechanical states possibly arising in environments such as active galactic nuclei, has been proposed to explain these and other associated observations with FRBs (e.g. high event rate, repeatability, variable intensity profiles).[85] In July 2019, astronomers reported that non-repeating Fast Radio Bursts may not be one-off events, but actually FRB repeaters with repeat events that have gone undetected and, further, that FRBs may be formed by events that have not yet been seen or considered.[86][87] Additional possibilities include that FRBs may originate from nearby stellar flares.[88] A FRB with multiple periodic component peaks lasting over 3 seconds was reported in 2022. A neutron star has been proposed as the origin of this FRB.[23]

Bursts observed

[edit]

Naming

[edit]

Fast radio bursts are named by the date the signal was recorded, as "FRB YYMMDD", with a letter appended to distinguish multiple sources first recorded on the same date.

The name is of the presumed source rather than the burst of radio waves, so repeated or subsequent bursts from the same apparent location (eg, FRB 121102) do not get new date names.

2007 (Lorimer Burst)

[edit]

The first FRB detected, the Lorimer Burst FRB 010724, was discovered in 2007 when Duncan Lorimer of West Virginia University assigned his student David Narkevic to look through archival data taken in 2001 by the Parkes radio dish in Australia.[56] Analysis of the survey data found a 30-jansky dispersed burst which occurred on 24 July 2001,[1] less than 5 milliseconds in duration, located 3° from the Small Magellanic Cloud. The reported burst properties argue against a physical association with the Milky Way galaxy or the Small Magellanic Cloud.[89] The discoverers argue that current models for the free electron content in the Universe imply that the burst is less than 1 gigaparsec distant. The fact that no further bursts were seen in 90 hours of additional observations implies that it was a singular event such as a supernova or merger of relativistic objects.[1] It is suggested that hundreds of similar events could occur every day and if detected could serve as cosmological probes.[1]

2010

[edit]
A peryton event detected at the Parkes Observatory. Peryton events are now known to be caused by the emission from a microwave oven.

In 2010 there was a report of 16 similar pulses, clearly of terrestrial origin, detected by the Parkes radio telescope and given the name perytons.[90] In 2015 perytons were shown to be generated when microwave oven doors were opened during a heating cycle, with detected emission being generated by the microwave oven's magnetron tube as it was being powered off.[91]

2011

[edit]

In 2015, FRB 110523 was discovered in archival data collected in 2011 from the Green Bank Telescope.[51] It was the first FRB for which linear polarization was detected (allowing a measurement of Faraday rotation). Measurement of the signal's dispersion delay suggested that this burst was of extragalactic origin, possibly up to 6 billion light-years away.[92]

2012

[edit]

Victoria Kaspi of McGill University estimated that as many as 10,000 fast radio bursts may occur per day over the entire sky.[93]

FRB 121102

[edit]

An observation in 2012 of a fast radio burst (FRB 121102)[9] in the direction of Auriga in the northern hemisphere using the Arecibo radio telescope confirmed the extragalactic origin of fast radio pulses by an effect known as plasma dispersion.

In November 2015, astronomer Paul Scholz at McGill University in Canada, found ten non-periodically repeated fast radio pulses in archival data gathered in May and June 2015 by the Arecibo radio telescope.[94] The ten bursts have dispersion measures and sky positions consistent with the original burst FRB 121102, detected in 2012.[94] Like the 2012 burst, the 10 bursts have a plasma dispersion measure that is three times larger than possible for a source in the Milky Way Galaxy. The team thinks that this finding rules out self-destructive, cataclysmic events that could occur only once, such as the collision between two neutron stars.[95] According to the scientists, the data support an origin in a young rotating neutron star (pulsar), or in a highly magnetized neutron star (magnetar),[94][95][96][97][9] or from highly magnetized pulsars travelling through asteroid belts,[98] or from an intermittent Roche lobe overflow in a neutron star-white dwarf binary.[99]

On 16 December 2016 six new FRBs were reported in the same direction (one having been received on 13 November 2015, four on 19 November 2015, and one on 8 December 2015).[100]: Table 2  As of January 2019 this is one of only two instances in which these signals have been found twice in the same location in space. FRB 121102 is located at least 1150 AU from Earth, excluding the possibility of a human-made source, and is almost certainly extragalactic in nature.[100]

As of April 2018, FRB 121102 is thought to be co-located in a dwarf galaxy about three billion light-years from Earth with a low-luminosity active galactic nucleus, or a previously unknown type of extragalactic source, or a young neutron star energising a supernova remnant.[101][102][24][103][104][105]

On 26 August 2017, astronomers using data from the Green Bank Telescope detected 15 additional repeating FRBs coming from FRB 121102 at 5 to 8 GHz. The researchers also noted that FRB 121102 is presently in a "heightened activity state, and follow-on observations are encouraged, particularly at higher radio frequencies".[106][8][107] The waves are highly polarized and undergo Faraday rotation, meaning "twisting" transverse waves, that could have formed only when passing through hot plasma with an extremely strong magnetic field.[108] This rotation of polarized light is quantified by Rotation Measure (RM). FRB 121102's radio bursts have RM about 500 times higher than those from any other FRB to date.[108] Since it is a repeating FRB source, it suggests that it does not come from some one-time cataclysmic event; so one hypothesis, first advanced in January 2018, proposes that these particular repeating bursts may come from a dense stellar core called a neutron star near an extremely powerful magnetic field, such as one near a massive black hole,[108] or one embedded in a nebula.[109]

In April 2018, it was reported that FRB 121102 consisted of 21 bursts spanning one hour.[110] In September 2018, an additional 72 bursts spanning five hours had been detected using a convolutional neural network.[111][112][113] In September 2019, more repeating signals, 20 pulses on 3 September 2019, were reported to have been detected from FRB 121102 by the Five-hundred-meter Aperture Spherical Telescope (FAST).[114] In June 2020, astronomers from Jodrell Bank Observatory reported that FRB 121102 exhibits the same radio-burst behavior ("radio bursts observed in a window lasting approximately 90 days followed by a silent period of 67 days") every 157 days, suggesting that the bursts may be associated with "the orbital motion of a massive star, a neutron star or a black hole".[115] Subsequent studies by FAST of further activity, consisting of 12 bursts within two hours observed on 17 August 2020, supports an updated refined periodicity between active periods of 156.1 days.[116] Related studies have been reported in October 2021.[40][41] Further bursts, at least 300, were detected by FAST in August and September 2022.[117] Further related studies were reported in April 2023.[118] In July 2023 19 new burst were reported from existing observations of 121102A that were taken by the Green Bank Telescope, eight of which were extremely short, independent, bursts lasting between 5 and 15 microseconds, the shortest so far detected.[119]

2013

[edit]

In 2013, four bursts were identified that supported the likelihood of extragalactic sources.[120]

2014

[edit]

In 2014, FRB 140514 was caught 'live' and was found to be 21% (±7%) circularly polarised.[44]

2015

[edit]

FRB 150418

[edit]

On 18 April 2015, FRB 150418 was detected by the Parkes observatory and within hours, several telescopes including the Australia Telescope Compact Array caught an apparent radio "afterglow" of the flash, which took six days to fade.[121][122][123] The Subaru Telescope was used to find what was thought to be the host galaxy and determine its redshift and the implied distance to the burst.[124]

However, the association of the burst with the afterglow was soon disputed,[125][126][127] and by April 2016 it was established that the "afterglow" originated from an active galactic nucleus (AGN) that is powered by a supermassive black hole with dual jets blasting outward from the black hole.[128] It was also noted that what was thought to be an afterglow did not fade away as would be expected, supporting the interpretation that it originated in the variable AGN and was not associated with the fast radio burst.[128]

2017

[edit]

The upgraded Molonglo Observatory Synthesis Telescope (UTMOST), near Canberra (Australia), reported finding three more FRBs.[129] A 180-day three-part survey in 2015 and 2016 found three FRBs at 843 MHz.[49] Each FRB located with a narrow elliptical 'beam'; the relatively narrow band 828–858 MHz gives a less precise dispersion measure (DM).[49]

A short survey using part of Australian Square Kilometre Array Pathfinder (ASKAP) found one FRB in 3.4 days. FRB170107 was bright with a fluence of 58±6 Jy ms.[50][130]

According to Anastasia Fialkov and Abraham Loeb, FRB's could be occurring as often as once per second. Earlier research could not identify the occurrence of FRB's to this degree.[131]

2018

[edit]
Artist's impression of a fast radio burst FRB 181112 traveling through space and reaching Earth.[132]

Three FRBs were reported in March 2018 by Parkes Observatory in Australia. One (FRB 180309) had the highest signal-to-noise ratio yet seen of 411.[133][134]

The unusual CHIME (Canadian Hydrogen Intensity Mapping Experiment) radio telescope, operational from September 2018, can be used to detect "hundreds" of fast radio bursts as a secondary objective to its cosmological observations.[135][94] FRB 180725A was reported by CHIME as the first detection of a FRB under 700 MHz – as low as 580 MHz.[136][137]

In October 2018, astronomers reported 19 more new non-repeating FRB bursts detected by the Australian Square Kilometre Array Pathfinder (ASKAP).[138][139] These included three with dispersion measure (DM) smaller than seen before : FRB 171020 (DM=114.1), FRB 171213 (DM=158.6), FRB 180212 (DM=167.5).[140]

FRB 180814

[edit]

On 9 January 2019, astronomers announced the discovery of a second repeating FRB source, named FRB 180814, by CHIME. Six bursts were detected between August and October 2018, "consistent with originating from a single position on the sky". The detection was made during CHIME's pre-commissioning phase, during which it operated intermittently, suggesting a "substantial population of repeating FRBs", and that the new telescope would make more detections.[10][141]

Some news media reporting of the discovery speculated that the repeating FRB could be evidence of extraterrestrial intelligence,[142][143] a possibility explored in relation to previous FRBs by some scientists,[61][144] but not raised by the discoverers of FRB 180814.[10][141]

FRB 180916

[edit]
Main article: FRB 180916.J0158+65

FRB 180916,[145] more formally FRB 180916.J0158+65, is a repeating FRB discovered by CHIME, that later studies found to have originated from a medium-sized spiral galaxy (SDSS J015800.28+654253.0) about 500 million light-years away – the closest FRB discovered to date.[146][27][28] It is also the first FRB observed to have a regular periodicity. Bursts are clustered into a period of about four days, followed by a dormant period of about 12 days, for a total cycle length of 16.35±0.18 days.[13][147][148] Additional followup studies of the repeating FRB by the Swift XRT and UVOT instruments were reported on 4 February 2020;[149] by the Sardinia Radio Telescope (SRT) and Medicina Northern Cross Radio Telescope (MNC), on 17 February 2020;[150] and, by the Galileo telescope in Asiago, also on 17 February 2020.[151] Further observations were made by the Chandra X-ray Observatory on 3 and 18 December 2019, with no significant x-ray emissions detected at the FRB 180916 location, or from the host galaxy SDSS J015800.28+654253.0.[152] On 6 April 2020, followup studies by the Global MASTER-Net were reported on The Astronomer's Telegram.[153] On 25 August 2021, further observations were reported.[154][155]

FRB 181112

[edit]

FRB 181112 was mysteriously unaffected after believed to have passed through the halo of an intervening galaxy.[156]

2019

[edit]

FRB 180924

[edit]

FRB 180924 is the first non-repeating FRB to be traced to its source. The source is a galaxy 3.6 billion light-years away. The galaxy is nearly as large as the Milky Way and about 1000 times larger than the source galaxy of FRB 121102. While the latter is an active site of star formation and a likely place for magnetars, the source of FRB 180924 is an older and less active galaxy.[157][158][159]

Because the FRB was nonrepeating, the astronomers had to scan large areas with the 36 telescopes of ASKAP. Once a signal was found, they used the Very Large Telescope, the Gemini Observatory in Chile, and the W. M. Keck Observatory in Hawaii to identify its host galaxy and determine its distance. Knowledge of the distance and source galaxy properties enables a study of the composition of the intergalactic medium.[158]

June 2019

[edit]

On 28 June 2019, Russian astronomers reported the discovery of nine FRB events (FRB 121029, FRB 131030, FRB 140212, FRB 141216, FRB 151125.1, FRB 151125.2, FRB 160206, FRB 161202, FRB 180321), which include FRB 151125, the third repeating one ever detected, from the direction of the M 31 (Andromeda Galaxy) and M 33 (Triangulum Galaxy) galaxies during the analysis of archive data (July 2012 to December 2018) produced by the BSA/LPI large phased array radio telescope at the Pushchino Radio Astronomy Observatory.[11][160][12]

FRB 190520

[edit]

FRB 190520 was observed by the FAST telescope and was localized using the realfast[161] system at the Karl G. Jansky Very Large Array (VLA). Optical observations using the Palomar 200-inch Hale Telescope revealed a host dwarf galaxy at redshift z=0.241. This is the second FRB observed to have an associated Persistent Radio Source (PRS). The dispersion measure(DM) and rotation measure measurements reveals a very dense, magnetized and turbulent environment local to the source. In June 2022, astronomers reported that FRB 20190520B was found to be another repeating FRB.[162] On 12 May 2023, FRB 20190520B was reported to show multiple bursts indicating magnetic field reversal.[163]

FRB 190523

[edit]

On 2 July 2019, astronomers reported that FRB 190523, a non-repeating FRB, has been discovered and, notably, localized to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66, nearly 8 billion light-years away from Earth.[164][165]

August 2019

[edit]

In August 2019, the CHIME Fast Radio Burst Collaboration reported the detection of eight more repeating FRB signals.[25][26]

FRB 191223

[edit]

On 29 December 2019, Australian astronomers from the Molonglo Observatory Synthesis Telescope (MOST), using the UTMOST fast radio burst equipment, reported the detection of FRB 191223 in the Octans constellation (RA = 20:34:14.14, DEC = -75:08:54.19).[166][167]

FRB 191228

[edit]

On 31 December 2019, Australian astronomers, using the Australian Square Kilometre Array Pathfinder (ASKAP), reported the detection of FRB 191228 in the Piscis Austrinus constellation (RA = 22:57(2), DEC = -29:46(40)).[166][168]

2020

[edit]

FRB 200120E

[edit]

In February & March 2022, astronomers reported that a globular cluster of M81, a grand design spiral galaxy about 12 million light-years away, may be the source of FRB 20200120E, a repeating fast radio burst.[169][170][171]

FRB 200317

[edit]

Astronomers reported the discovery of FRB 20200317A (RA 16h22m45s, DEC p+56d44m50s) with FAST (Five-hundred-meter Aperture Spherical radio Telescope) in archival data on 22 September 2023. The detected FRB is "one of the faintest FRB sources detected so far", according to the report.[172]

FRB 200428

[edit]

On 28 April 2020, astronomers at the Canadian Hydrogen Intensity Mapping Experiment (CHIME), reported the detection of a bright radio burst from the direction of the Galactic magnetar SGR 1935+2154 about 30,000 light years away in the Vulpecula constellation.[173][174][175] The burst had a DM of 332.8 pc/cc.[173] The STARE2[176] team independently detected the burst and reported that the burst had a fluence of >1.5 MJy ms, establishing the connection between this burst and FRBs at extragalactic distances.[36] The burst was then referred to as FRB 200428.[177] The detection is notable, as the STARE2 team claim it is the first ever FRB detected inside the Milky Way, and the first ever to be linked to a known source.[30][31] That link strongly supports the idea that fast radio bursts emanate from magnetars.[178]

FRB 200610

[edit]

On 10 January 2024, astronomers reported that the source of FRB 20200610A was a "rare 'blob-like' group of galaxies".[179]

FRBs 200914 and 200919

[edit]

On 24 September 2020, astronomers reported the detection of two new FRBs, FRB200914 and FRB200919, by the Parkes Radio Telescope.[180] Upper limits on low-frequency emission from FRB 200914 were later reported by the Square Kilometre Array radio telescope project.[181]

FRB 201124

[edit]

On 31 March 2021, the CHIME/FRB Collaboration reported the detection of FRB 20201124A and related multiple bursts within the week of 23 March 2021 — designated as 20210323A, 20210326A, 20210327A, 20210327B, 20210327C, and 20210328A[182] — and later, likely 20210401A[183] and 20210402A.[184] Further related observations were reported by other astronomers on 6 April 2021,[185] 7 April 2021,[186][187] and many more as well,[188] including an "extremely bright" pulse on 15 April 2021.[189] Source localization improvements were reported on 3 May 2021.[190] Even more observations were reported in May 2021,[191] including "two bright bursts".[192] On 3 June 2021, the SETI Institute announced detecting "a bright double-peaked radio burst" from FRB 201124A on 18 May 2021.[193][194] Further observations were made by the Neil Gehrels Swift Observatory on 28 July 2021 and 7 August 7, 2021 without detecting a source on either date.[195] On 23 September 2021, 9 new bursts from FRB 20201124A were reported to have been observed with the Effelsberg 100-m Radio Telescope, followed by one CHIME observation, all after four months of no detections.[196] In January and February 2022, further observations of new bursts from FRB 20201124A with the Westerbork-RT1 25-m telescope were also reported.[197][198][199] In mid-March 2022, further observations of FRB 20201124 were reported.[200][201][202] In September 2022, astronomers suggested that the repeating FRB 20201124A may originate from a magnetar/Be star binary.[203][204]

2021

[edit]

FRB 210401

[edit]

On 2 and 3 April 2021, astronomers at the Australian Square Kilometre Array Pathfinder (ASKAP) reported the detection of FRB 20210401A and 20210402A which were understood likely to be repetitions of FRB 20201124A, a repeating FRB with recent very high burst activity, that was reported earlier by the CHIME/FRB collaboration.[182][183][184]

FRB 210630

[edit]

On 30 June 2021, astronomers at the Molonglo Observatory Synthesis Telescope (UTMOST) detected FRB 210630A at the "likely" position of "RA = 17:23:07.4, DEC =+07:51:42, J2000".[205]

FRB 211211

[edit]

On 15 December 2021, astronomers at the Neil Gehrels Swift Observatory reported further observations of the "bright CHIME FRB 20211122A (event #202020046 T0: 2021-12-11T16:58:05.183768)".[206]

2022

[edit]

FRB 220414

[edit]

On 14 April 2022, astronomers at Tianlai Cylinder Pathfinder Array (a radio interferometer located in Xinjiang, China, operated by the National Astronomical Observatory, Chinese Academy of Sciences (NAOC)) detected FRB 220414 (?) ("A bright burst was detected with a S/N~15 for ~2.2 ms duration at UT 17:26:40.368, April 14, 2022 (MJD 59684.06018945136)") located at "RA = 13h04m21s(\pm 2m12s), DEC = +48\deg18'05"(\pm 10'19")".[207]

FRB 220610

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On 19 October 2023, astronomers reported that FRB 20220610A traveled for 8 billion years to reach Earth equivalent at a redshift of making it the oldest FRB known and also calculated to be the most energetic one with a spectral energy density of ~6.4×1032erg/Hz and a maximum burst energy of ~2×1042erg higher than the previous predicted maximum energy for FRBs.[208][209][210][211] In January 2024, further detailed observations and studies were reported.[212]

FRB 220912

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On 15 October 2022, astronomers at CHIME/FRB reported the detection of nine bursts in three days of FRB 20220912A.[213] Since later bursts observed between 15 October 2022 and 29 October 2022 by the CHIME/FRB collaboration, astronomers, afterwards, at the Allen Telescope Array (ATA), on 1 November 2022, reported eight more bursts from FRB 20220912A. ATA coordinates were first set to the original settings (23h09m05.49s + 48d42m25.6s) and then later to the newly updated ones (23h09m04.9s +48d42m25.4s).[214] On 13 November 2022, further burst activity of FRB 20220912A was reported by the Tianlai Dish Pathfinder Array in Xinjiang, China[215] and, on 5 December 2022, from several other observatories.[216] On 13 December 2022, over a hundred bursts from FRB 220912A were reported by the Upgraded Giant Metrewave Radio Telescope (uGMRT), operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research in India.[217] On 21 December 2022, several more bright bursts of FRB 220912A using the Westerbork-RT1 were reported.[218] Four more bursts were reported on 13 July 2023 by the Medicina Radio Observatory (specifically by the Medicina Northern Cross (MNC) radio telescope) in Bologna, Italy.[219] Based on four bursts, burst rate constraints of FRB 20220912A at various frequencies using the Green Bank 20-meter telescope were reported on 18 August 2023.[220] Swift X-ray observations were reported on 1 September 2023.[221]

FRB 191221

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On 13 July 2022, the discovery of an unusual FRB 20191221A detected by CHIME was reported. It is a multicomponent pulse (nine or more components) with peaks separated by 216.8ms and lasting an unusually long duration of three seconds. This is the first time such a periodic pulse was detected.[23]

FRB 221128

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On 1 December 2022, astronomers reported the discovery of FRB 20221128A, using the UTMOST-NS radio telescope located in New South Wales, Australia. According to the astronomers, "The most likely position [of FRB 20221128A] is RA = 07:30(10), DEC = -41:32(1), J2000 which corresponds to Galactic coordinates: Gl = 177.1 deg, Gb = 24.45 deg".[222] Later, on 19 January 2023, a corrected position [of FRB 20221128A] was reported as follows: "The revised FRB position is RA = 07:30(10), DEC = -42:30(1) in equatorial (J2000) coordinates, which corresponds to Galactic coordinates: Gl = 255.1 deg, Gb = -11.4 deg (we additionally note that the Galactic coordinates in ATel #15783 were in error)".[223]

FRB 221206

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On 6 December 2022, detection of a possible magnetar gamma-ray burst at or near the same time and location as a fast radio burst was reported.[224]

2023

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FRB 230814

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Discovery of FRB 20230814A by the Deep Synoptic Array DSA-110 was reported on 16 August 2023, and was determined to be localized (preliminarily) at 22h23m53.9s +73d01m33.3s (J2000).[225]

FRB 230905

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Observations of FRB 20230905 in the X-ray and UV range by the Neil Gehrels Swift Observatory was reported as bright and non-repeating on 7 September 2023.[226]

2024

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FRB 240114

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Discovery of a new repeating FRB 20240114A by the CHIME/FRB Collaboration (at position RA (J2000): 321.9162 +- 0.0087 deg, Dec (J2000): 4.3501 +- 0.0124 degrees) was reported on 26 January 2024. The three bursts from the FRB were detected at "2024-01-14 21:50:39, 2024-01-21 21:30:40, and 2024-01-24 21:20:11 UTC", and associated with a galaxy cluster at 425 Mpc.[227][228] On 5 February 2024, observations of five repeated bursts of FRB 20240114A on 2 February 2024 were reported using the Parkes/Murriyang Ultra Wideband Low (UWL) receiver system.[229][230] Also on 5 February 2024, a FRB detection was reported by the Westerbork RT1 25-m telescope.[231] On 8 February 2024, related observations of FRB 20240114A were reported by FAST (38 bursts from 28 January to 4 February)[232][233] and the Northern Cross Radio Telescope (1 burst on 1 February).[234] Detection and localization studies of FRB 20240114A by MeerKAT in South Africa were reported on 14 February 2024.[235] On 15 February 2024, 10 bursts were reported to have been detected on 1 February 2024 by the Giant Metrewave Radio Telescope (GMRT) in India.[236] On 29 February 2024, 51 bursts (including micro-structure) on 25 February 2024 using uGMRT were reported.[237] On 5 March 2024, a "burst storm" was reported from FRB 20240114A by the FAST radio telescope.[238] On 20 March 2024, the European VLBI Network (EVN) reported several detailed studies, which included observations on 15 February 2024 (7 bursts) and 20 February 2024 (13 bursts), of FRB 20240114A was observed on 17 March 2024240114A.[239] On 21 March 2024, the Northern Cross Radio Telescope in Italy reported a bright radio burst of FRB 20240114A, at updated coordinates of R.A.: 21:27:39.84, Dec: +04:19:46.34 (J2000), on 17 March 2024.[240] On 2 April 2024, astronomers report over 100 detections of FRB 20240114A using five small European radio telescopes.[241] On 18 April 2024, a coincident gamma-ray emission was observed possibly associated with FRB 20240114A.[242] On 23 April 2024, five repeat bursts from FRB 20240114A were reported to have been detected by the Nancay Radio Telescope at 2.5 GHz ("highest frequency to date") on 18 April 2024.[243] On 25 April 2024, eight repeat bursts from FRB 20240114A were reported to have been detected by the Allen Telescope Array (ATA) at frequencies above 2.0 GHz.[244] On 26 April 2024, no counterpart candidates (ie, "no significance gamma-ray emission") from FRB 20240114A were reported to have been observed by Fermi-LAT.[245] On 4 May 2024, astronomers reported a redshift (ie, "a common redshift of z=0.1300+/-0002") for the FRB host galaxy, possibly a dwarf star-forming galaxy.[246] Astronomers, on 15 May 2024, reported multiple burst detections of FRB 20240114A up to 6 GHz using the Effelsberg 100-m Radio Telescope.[247] A gamma-ray flare associated with FRB 20240114A was reported on 25 May 2024.[248]

FRB 240216

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Announcement of five bursts from FRB 20240216A, a new repeating fast radio burst source, detected by Australian SKA Pathfinder (ASKAP) at position (J2000) of RA: 10:12:19.9 DEC: +14:02:26, was reported on 22 February 2024.[249] FAST, on February 24, 2024, reported no detection, with several explanations, of FRB 20240216A.[250]

List of notable bursts

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Main article: List of fast radio bursts

All FRBs are cataloged at TNS.[251]

Name Date and time (UTC) for 1581.804688 MHz RA
(J2000) 		Decl.
(J2000) 		DM
(pc·cm−3) 		Width
(ms) 		Peak flux
(Jy) 		Notes
FRB 010621[252] 2001-06-21 13:02:10.795 18h 52m −08° 29′ 746 7.8 0.4
FRB 010724[1] 2001-07-24 19:50:01.63 01h 18m −75° 12′ 375 4.6 30 "Lorimer Burst"
FRB 011025[253] 2001-10-25 00:29:13.23 19h 07m −40° 37′ 790 9.4 0.3
FRB 090625[67] 2009-06-25 21:53:52.85 03h 07m −29° 55′ 899.6 <1.9 >2.2
FRB 110220[120] 2011-02-20 01:55:48.957 22h 34m −12° 24′ 944.38 5.6 1.3
FRB 110523 [92][51] 2011-05-23 21h 45m −00° 12′ 623.30 1.73 0.6 700–900 MHz at Green Bank radio telescope, detection of both circular and linear polarization.
FRB 110627[120] 2011-06-27 21:33:17.474 21h 03m −44° 44′ 723.0 <1.4 0.4
FRB 110703[120] 2011-07-03 18:59:40.591 23h 30m −02° 52′ 1103.6 <4.3 0.5
FRB 120127[120] 2012-01-27 08:11:21.723 23h 15m −18° 25′ 553.3 <1.1 0.5
FRB 121002[254] 2012-10-02 13:09:18.402 18h 14m −85° 11′ 1628.76 2.1; 3.7 0.35 double pulse 5.1 ms apart
FRB 121002[67] 2012-10-02 13:09:18.50 18h 14m −85° 11′ 1629.18 <0.3 >2.3
FRB 121102[255] 2012-11-02 06:35:53.244 05h 32m +33° 05′ 557 3.0 0.4 by Arecibo radio telescope

Repeating bursts,[106][8][100][24] very polarized.

FRB 130626[67] 2013-06-26 14:56:00.06 16h 27m −07° 27′ 952.4 <0.12 >1.5
FRB 130628[67] 2013-06-28 03:58:00.02 09h 03m +03° 26′ 469.88 <0.05 >1.2
FRB 130729[67] 2013-07-29 09:01:52.64 13h 41m −05° 59′ 861 <4 >3.5
FRB 131104[256] 2013-11-04 18:04:01.2 06h 44m −51° 17′ 779.0 <0.64 1.12 'near' Carina Dwarf Spheroidal Galaxy
FRB 140514[257] 2014-05-14 17:14:11.06 22h 34m −12° 18′ 562.7 2.8 0.47 21 ±7 per cent (3σ) circular polarization
FRB 150215[258][259] 2015-02-15 20:41:41.714 18h 17m 27s −04° 54′ 15″ 1105.6 2.8 0.7 43% linear, 3% circular polarized. Low galactic latitude. Low/zero rotation measure. Detected in real time. Not detected in follow up observations of gamma rays, X-rays, neutrinos, IR etc.[258]
FRB 150418 2015-04-18 04:29 07h 16m −19° 00′ 776.2 0.8 2.4 Detection of linear polarization. The origin of the burst is disputed.[125][126][127][128]
unnamed 2015-05-17
2015-06-02		 05h 31m 58s (average) +33° 08′ 04″ (average) 559 (average) 0.02–0.31 2.8–8.7 10 repeat bursts at FRB 121102 location: 2 bursts on May 17 and 8 bursts on June 2[96][97]
and 1 on 13 Nov 2015, 4 on 19 Nov 2015, and 1 on 8 Dec 2015[100]
FRB 150610 2015-06-10 05:26:59.396 10:44:26 −40:05:23 1593.9(±0.6) 2(±1) 0.7(±0.2)
FRB 150807[260] 2015-08-07 17:53:55.7799 22:40:23 – 55:16 266.5 0.35±0.05 120±30 80% linearly polarised, Galactic latitude −54.4°, Decl ±4 arcmin, RA ±1.5 arcmin,[260] highest peak flux
FRB 151206 2015-12-06 06:17:52.778 19:21:25 −04:07:54 1909.8(±0.6) 3.0(±0.6) 0.3(±0.04)
FRB 151230 2015-12-30 16:15:46.525 09:40:50 −03:27:05 960.4(±0.5) 4.4(±0.5) 0.42(±0.03)
FRB 160102 2016-01-02 08:28:39.374 22:38:49 −30:10:50 2596.1(±0.3) 3.4(±0.8) 0.5(±0.1)
FRB 160317[49] 2016-03-17 09:00:36.530 07:53:47 −29:36:31 1165(±11) 21 >3.0 UTMOST, Decl ± 1.5°[49]: Table A1 
FRB 160410[49] 2016-04-10 08:33:39.680 08:41:25 +06:05:05 278(±3) 4 >7.0 UTMOST, Decl ± 1.5°[49]: Table A1 
FRB 160608[49] 2016-06-08 03:53:01.088 07:36:42 −40:47:52 682(±7) 9 >4.3 UTMOST, Decl ± 1.5°[49]: Table A1 
FRB 170107[50] 2017-01-07 20:05:45.1397 11:23 – 05:01 609.5(±0.5) 2.6 27±4 first by ASKAP, high fluence ~58 Jy ms. In Leo. Galactic latitude 51°, Distance 3.1 Gpc, isotropic energy ~3 x 1034 J[50]
unnamed 2017-08-26 13:51:44 05h 32m +33° 08′ 558(approx) ? ? 15 more bursts at the location of FRB 121102 detected by Green Bank Telescope over a 24-minute interval, bringing the total received bursts from this location to 34.[106]
FRB 170827[261] 2017-08-27 16:20:18 00h 49m 18.66s −65° 33′ 02.3″ 176.4 0.395 low DM
FRB 170922[262] 2017-09-22z 11:23:33.4 21h 29m 50.61s −07° 59′ 40.49″ 1111 26 extreme scattering (long pulse)
FRB 171020 2017-10-20 10:27:58.598 22:15 – 19:40 114.1±0.2 3.2 ASKAP s/n=19.5 G-Long'=29.3 G-lat'=-51.3 Lowest DM so far.[134]
FRB 171209[263] 2017-12-09 20:34:23.5 15h 50m 25s −46° 10′ 20″ 1458 2.5 2.3 Seems to be in the same location as GRB 110715A[29]
FRB 180301[264] 2018-03-01 07:34:19.76 06h 12m 43.4s +04° 33′ 44.8″ 520 3 0.5 positive spectrum, from Breakthrough Listen
FRB 180309[265] 2018-03-09 02:49:32.99 21h 24m 43.8s −33° 58′ 44.5″ 263.47 0.576 12
FRB 180311[266] 2018-03-11 04:11:54.80 21h 31m 33.42s −57° 44′ 26.7″ 1575.6 12 2.4
FRB 180725A[137][267] 2018-07-25 17:59:43.115 06h 13m 54.7s +67° 04′ 00.1″ 716.6 2 first detection of an FRB at radio frequencies below 700 MHz
Realtime detection by CHIME.
FRB 180814.2[10] 2018-08-14 14:49:48.022 04h 22m 22s +73° 40′ 189.38±0.09 2.6±0.2 8.1 Detected by CHIME. Second repeating FRB to be discovered and first since 2012.
FRB 180916 2018-09-16 10:15:19.803 01h 58m 00.75s +65° 43′ 00.5″ 349.2±0.4 1.4±0.07 1.4±0.6 repeating FRB localized to a nearby (450 million lyr) spiral galaxy. 16.35 day periodicity.[14]
FRB 180924[157] 2018-09-24 16:23:12.6265 21h 44m 25.26s −40° 54′ 0.1″ 361.42 1.3 16 first non-repeating FRB whose source has been localized; a galaxy 3.6 billion light-years away
FRB 190523 Date/Time RA DEC DM Width Peak flux A non-repeating FRB – localised to a galaxy at nearly 8 billion lyr
FRB 200428 2020-04-28 19h 35m +21° 54′ 332.8 — — first ever detected FRB inside the Milky Way about 30,000 lyr; first ever linked to a known source: the magnetar SGR 1935+2154
FRB 201124 2020-11-24 08:50:41 05h 08m +26° 11′ 76 - 109 — — very high repeating burst activity reported to have begun 23 March 2021,[182][183][184][188] includes an "extremely bright" pulse on 15 April 2021.[189]
FRB 240114 2024-01-14 21:20:11 21h 28m +04:20° DM Width Peak flux multiple repeating FRB bursts

See also

[edit]

References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Fast radio burst

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Fast radio bursts (FRBs) are extremely bright, millisecond-duration transients of radio emission typically originating from extragalactic sources, typically lasting between 1 and 10 milliseconds and detectable across a broad bandwidth of 1 to 10 GHz. These bursts are characterized by high luminosities, often exceeding 10^{38} erg in the radio band, and exhibit dispersion measures that indicate propagation through the ionized intergalactic medium, allowing astronomers to estimate their cosmological distances, sometimes billions of light-years away. First discovered in 2007 through archival data from the Parkes radio telescope in —the so-called Lorimer burst—FRBs are estimated to occur at rates of thousands per day across the sky, with over 4,000 detected and around 120 unique sources localized to host galaxies as of November 2025. The initial detection sparked intense interest due to the bursts' unexpected properties, including their high fluence (energy flux) and apparent one-off nature for most events, though only about 3% are found to repeat irregularly, sometimes hundreds of times. Repeating FRBs, such as FRB 121102, have enabled precise localization to dwarf galaxies with elevated rates, suggesting a link to young stellar populations. Non-repeating FRBs, which comprise the majority, are harder to pinpoint but contribute to statistical studies of their distribution and energetics. Advances in radio telescopes like the Canadian Intensity Mapping Experiment (CHIME) and the Five-hundred-meter Aperture Spherical radio Telescope (FAST) have dramatically increased detection rates, revealing diverse morphologies, including periodicities in some repeaters that hint at underlying periodic drivers. While the exact mechanisms producing FRBs remain uncertain, leading theories propose emission from highly magnetized known as magnetars, potentially triggered by starquakes or accretion events in their vicinity. Other models include mergers or extreme plasma processes in young magnetars within remnants, supported by the association of some FRBs with persistent radio sources resembling wind nebulae. FRBs hold significant potential for cosmology, as their dispersion measures can probe the diffuse baryonic matter in the intergalactic medium, helping to resolve the "missing baryons" problem, and for testing fundamental , such as Lorentz invariance at high energies. Ongoing multi-wavelength follow-up observations continue to refine these insights, with recent localizations confirming extragalactic origins for even the brightest events.

Discovery and Detection

Initial Discovery

The first fast radio burst (FRB), designated FRB 010724 and commonly known as the Lorimer burst, was identified in 2007 by Duncan Lorimer and his student David Narkevic while examining archival data from a 2001 pulsar survey conducted with the in . The signal featured a high dispersion measure (DM) of 375 pc cm⁻³, far exceeding typical values for within the , prompting the initial conclusion that it was an extragalactic phenomenon originating from a distant cosmological source. This discovery, published in Science, marked the inception of FRB research, though the transient nature of the event—lasting only milliseconds—prevented immediate follow-up observations. Confirmation proved challenging due to the reliance on single-dish observations, which provided limited localization, and the absence of real-time detection capabilities at the time, meaning bursts were only recognized post hoc in archival datasets. A subsequent archival search yielded another dispersed burst in Parkes data from June 21, 2001 (FRB 010621, the Keane burst), reported in 2011, which shared similar properties but was later suggested to originate from a Galactic based on follow-up studies. Additional FRBs were uncovered in from further analysis of Parkes high-latitude survey data, bringing the total to five known events, all characterized by similar dispersive delays indicative of extragalactic propagation. Early skepticism arose regarding whether these signals were genuine astrophysical phenomena or artifacts of local interference, particularly since all initial detections originated from the Parkes telescope. This doubt intensified with the identification of perytons—terrestrial interference signals mimicking some FRB properties—originating from on-site microwave ovens at the observatory. The issue was resolved by 2014 through independent detections at other facilities, including the first non-Parkes FRB (FRB 121102) observed with the in 2012 data, confirming the extragalactic nature and ruling out site-specific contamination. The inaugural real-time detection occurred in 2014 with FRB 140514 at Parkes, enabling rapid multi-wavelength follow-up that bolstered confidence in the phenomenon's cosmic origin.

Detection Techniques and Surveys

Fast radio bursts (FRBs) are primarily detected using single-dish radio telescopes optimized for wide-field surveys, such as the in , the in (before its decommissioning in 2020), and the Canadian Hydrogen Intensity Mapping Experiment (CHIME) in . These instruments operate in the range, typically between 400 MHz and 1.4 GHz, where FRBs exhibit their characteristic dispersion due to interstellar and intergalactic plasma. To identify these millisecond-duration, chirped signals amid noise and radio-frequency interference, detection pipelines employ incoherent dedispersion algorithms, which trial a range of dispersion measures (DMs) by applying time delays to frequency channels and summing the intensity across the band. This brute-force approach, computationally intensive but effective for blind searches, compensates for the unknown DM without requiring phase-coherent information, enabling the identification of dispersed pulses that would otherwise smear over time. Major surveys have leveraged these techniques to systematically catalog FRBs, building on the initial serendipitous detections at Parkes in the late 2000s. The High Time Resolution Universe (HTRU) survey, conducted at Parkes throughout the 2010s, targeted high-latitude and galactic plane regions, yielding several FRBs through reprocessed data using advanced dedispersion and candidate verification methods; a 2024 reanalysis identified 18 additional bursts, nearly tripling the original tally. Similarly, the Arecibo Legacy Fast ALFA (ALFALFA) survey and its commensal ALFABURST extension detected isolated FRBs via single-pulse searches in pulsar data, contributing early examples before Arecibo's closure. The CHIME/FRB project, operational since 2018, represents a cornerstone of modern FRB surveys with its cylindrical reflector design providing a large (200 square degrees) and real-time processing capabilities, detecting over 4,500 FRB bursts by late 2023, with thousands more by November 2025 through a pipeline that includes incoherent dedispersion across 1024 frequency channels and automated alerting. For instance, in March 2025, CHIME detected the brightest FRB to date (FRB 20250316A), which was precisely localized using the CHIME Outriggers. For precise localization, the Australian Square Kilometre Array Pathfinder (ASKAP) employs interferometric arrays in its Commensal Real-time ASKAP Fast Transients () survey, achieving sub-arcsecond positions for dozens of FRBs by forming multiple tied-array beams and cross-correlating signals. Advancements in real-time detection have enhanced survey efficiency, with pipelines incorporating algorithms to filter candidates by scoring signal-to-noise ratios, morphology, and DM consistency, reducing false positives from terrestrial interference. Multi-telescope systems like MeerTRAP at the array in enable rapid follow-up by triggering coherent upon detection, localizing FRBs to within arcseconds and facilitating multi-wavelength observations within minutes. Recent surveys, such as the Apertif Radio Transient System (ARTS) at the Westerbork Synthesis Radio Telescope, have detected 18 new FRBs by 2025 using phased-array feeds for wide-field imaging and real-time transient searches. Complementing these efforts, the CHIME Outriggers—small interferometric telescopes positioned hundreds of kilometers from CHIME—provide for sub-arcsecond localizations, with initial operations in 2025 enabling host galaxy associations for nearby bursts.

Physical Properties

Temporal and Intensity Characteristics

Fast radio bursts (FRBs) are characterized by their extremely short durations, typically ranging from 1 to 10 milliseconds for non-repeating events, which defines their "fast" nature and distinguishes them from longer radio transients like pulsars. These bursts often exhibit intricate internal structures, including multiple sub-bursts and, in some cases, quasi-periodic patterns with periods on the order of milliseconds to hundreds of milliseconds, as observed in events like FRB 20220912A. For repeating FRBs, individual bursts can extend up to several seconds in duration, with complex temporal profiles that include downward-drifting sub-components in frequency-time plots, showing drift rates of a few GHz per second. In terms of intensity, FRBs display peak flux densities spanning 0.1 to 1200 Jy at gigahertz frequencies as of 2025, enabling detection across cosmological distances despite their brevity. The corresponding isotropic energies reach up to approximately 10^{40} erg, calculated from observed fluences and inferred distances, highlighting their immense . The fluence FF, which quantifies the total , is given by F=∫S(t) dt,F = \int S(t) \, dt, where S(t)S(t) is the flux density as a function of time tt; typical fluences range from 1 to hundreds of Jy ms. These properties imply extraordinarily high brightness temperatures exceeding 10^{36} K, necessitating coherent emission mechanisms to achieve such intensities from likely compact sources. Repeating FRBs exhibit variable repetition rates, from as frequent as seconds in active phases to intervals spanning months or years, as seen in sources like FRB 121102 and FRB 20201124A. This variability in timing, combined with the burst structures, suggests dynamic emission processes, though the overall temporal and intensity profiles remain broadly consistent with non-repeaters when normalized for distance.

Dispersion Measure and Distance Implications

The dispersion measure (DM) of a fast radio burst quantifies the integrated column of free s along the from the source to the observer, defined as DM=∫0Dne(l) dl\mathrm{DM} = \int_0^D n_e(l) \, dl, where nen_e is the and ll is the along the path. This excess induces a -dependent time delay in the arrival of the burst signal, given by Δt∝DM/ν2\Delta t \propto \mathrm{DM} / \nu^2, where ν\nu is the observing ; higher frequencies arrive earlier, allowing DM to be precisely measured from the burst's dynamic . In detection pipelines, this dispersive delay is modeled and corrected to dedisperse the signal and reveal its intrinsic temporal structure. The observed DM for an FRB is the sum of contributions from multiple components: the Milky Way's interstellar medium (DM_MW), the intergalactic medium (DM_IGM), and the host galaxy (DM_host), such that DM=DMMW+DMIGM+DMhost\mathrm{DM} = \mathrm{DM_{MW}} + \mathrm{DM_{IGM}} + \mathrm{DM_{host}}, with redshift corrections applied for cosmological propagation. The Galactic contribution, estimated using models like NE2001 or YMW16, typically ranges from 30 to 100 pc cm⁻³ depending on the line-of-sight direction through the disk and halo. Host galaxy contributions vary with galaxy type, size, and burst location but generally fall in the range of 50 to 200 pc cm⁻³ for localized FRBs in dwarf or star-forming galaxies, often dominated by the interstellar medium and circumgalactic halo. For extragalactic origins, the IGM component dominates at higher s, contributing hundreds to thousands of pc cm⁻³ for z>0.1z > 0.1, scaling roughly as DMIGM≈1000 z\mathrm{DM_{IGM}} \approx 1000 \, z pc cm⁻³ in the low-redshift limit due to ionized baryons in the cosmic web. By subtracting estimated DM_MW and DM_host from the total DM, the excess primarily traces DM_IGM, providing a direct measure of the ionized along the sightline and enabling (z) inference via the Macquart relation, which links DM_IGM to cosmological distance. This positions FRBs as powerful probes of missing baryonic matter, mapping the diffuse warm-hot intergalactic medium that constitutes much of the universe's ordinary matter otherwise hidden from optical or observations. As of 2025, observations of localized FRBs with host s have calibrated the average DM_IGM–z relation more precisely, incorporating host galaxy properties like and to reduce scatter from intrinsic variations, yielding DMIGM=(855±60)z(1+0.07z)\mathrm{DM_{IGM}} = (855 \pm 60) z (1 + 0.07 z) pc cm⁻³ and enabling constraints on cosmological parameters such as the Hubble constant. These relations confirm the extragalactic of FRBs and highlight their potential to trace feedback and large-scale structure evolution across cosmic history. For the repeating FRB 121102, the measured DM of approximately 557 pc cm⁻³, combined with its host of z≈0.193z \approx 0.193, implies an IGM contribution of around 360 pc cm⁻³ after subtracting Galactic (~58 pc cm⁻³) and host (~110 pc cm⁻³) components, consistent with expectations for a nearby extragalactic source. In contrast, the farthest FRB detected by 2025, FRB 20240304B at z≈2.15z \approx 2.15, exhibits a DM of 2458 pc cm⁻³, with an IGM contribution of approximately 2100 pc cm⁻³ after subtractions, underscoring how high-DM events probe the early universe's ionized fraction during cosmic noon.

Polarization and Multi-wavelength Features

Fast radio bursts (FRBs) often exhibit high degrees of , with fractions reaching up to nearly 100% in sources such as FRB 121102, suggesting emission from highly ordered in the source environment. This near-complete indicates coherent emission mechanisms, where the radio waves are generated in a structured or plasma, preserving the alignment of vectors. For instance, observations of FRB 20201124A show fractions exceeding 90% in many bursts, consistent with this interpretation. Faraday rotation measures (RMs) in FRBs can be exceptionally high, reaching values approximately 10^5 rad ^{-2} in the source frame, as seen in FRB 121102, which points to propagation through dense, magnetized plasma near the . These elevated RMs, far exceeding typical interstellar values, imply extreme magneto-ionic conditions, such as those around a young or in a , and often vary over time, reflecting dynamic environmental changes. In FRB 20201124A, RM variations of 500 rad ^{-2} on daily timescales further highlight these turbulent, magnetized surroundings. Circular polarization is rarer in FRBs and primarily observed in repeating sources, with fractions up to 90% detected in FRB 20201124A and other as of 2025, challenging models of pure linear emission and suggesting contributions from curved lines or mode conversion in the source plasma. Such high circular components, seen in less than 5% of bursts from active like FRB 20121102A and FRB 20190520B, imply intrinsically coherent processes that can produce both polarization modes, potentially linked to the high temperatures of FRB emission. These observations support scenarios involving magnetar-like objects where relativistic particles gyrate in strong fields, generating circularly polarized waves. Extensive multi-wavelength searches for FRB counterparts have yielded no confirmed detections in optical, , or gamma-ray bands for extragalactic FRBs as of November 2025, despite coordinated efforts with telescopes like Swift and Fermi, which provide stringent upper limits on associated emission. For example, simultaneous observations of repeating FRB 20220912A with Swift detected no or UV bursts coincident with radio pulses, setting upper limits on luminosities below 10^{42} erg s^{-1}. Fermi-LAT observations similarly constrain gamma-ray fluxes to below 10^{-12} erg cm^{-2} s^{-1} for most events, indicating that any high-energy counterparts are either faint or delayed relative to the radio prompt emission. Recent multi-wavelength follow-ups of bright events like FRB 20250316A also yield only upper limits on emission. A rare exception is FRB 200428, a Galactic event associated with gamma-ray and bursts from the SGR J1935+2154, marking the only confirmed multi-wavelength linkage to date. Scintillation and scattering effects significantly influence the observed temporal and spectral profiles of FRBs, broadening pulses and introducing modulation on timescales from milliseconds to seconds due to interstellar plasma turbulence. In the Milky Way, diffractive scintillation can cause flux variations, as observed in bright FRBs like FRB 150807, while scattering tails arise from multipath propagation delays, particularly at lower frequencies. These effects, modeled using two-screen approximations, help distinguish intrinsic burst properties from propagation-induced distortions and provide constraints on electron density models along the line of sight. For repeating sources like FRB 20201124A, annual variations in scintillation patterns reveal Galactic velocity components, aiding in source localization efforts.

Classification

Non-repeating FRBs

Non-repeating fast radio bursts (FRBs) represent the predominant class of these transients, accounting for approximately 96% of all detected FRBs based on surveys like the first CHIME/FRB catalog, which identified 474 one-off events out of 536 total bursts from 492 unique sources. Recent catalogs, such as the second CHIME/FRB catalog reporting over 4,500 bursts from thousands of unique sources as of 2025, maintain a similar high proportion of non-repeaters. Their sky distribution is isotropic, with no concentration toward the , consistent with an extragalactic population originating from cosmological distances. These bursts typically exhibit higher average dispersion measures (DMs) than repeating FRBs, often implying redshifts greater than 0.5 and corresponding to sources at distances exceeding hundreds of megaparsecs; for instance, mean excess DM values for non-repeaters are notably larger, reflecting greater interstellar medium contributions along their paths. They also display brighter fluences on average, enabling detection from farther cosmic volumes compared to the fainter emissions from repeaters. The all-sky event rate for non-repeating FRBs is estimated at around 10410^4 per day above a fluence threshold of approximately 1 Jy ms. The singular occurrence of these events severely limits follow-up observations, as transient telescopes cannot reliably target their positions without prior repetition to refine localizations, resulting in fewer multi-wavelength counterparts or host galaxy identifications relative to . This observational bias contributes to an inferred local volumetric rate of roughly 10310^3 Gpc−3^{-3} yr−1^{-1} for fluences above 2 Jy ms, derived from population synthesis models accounting for detection thresholds. Representative examples include FRB 180924, localized to a massive early-type galaxy at z=0.3214z = 0.3214 with a DM of 361 pc cm−3^{-3}, and FRB 190608, associated with a at z=0.118z = 0.118 featuring a DM of 338 pc cm−3^{-3}; both remain non-repeating as of 2025 with no subsequent bursts detected despite monitoring efforts. Unlike repeating FRBs, which enable repeated pointings for detailed characterization, these one-off events highlight the challenges in probing potential catastrophic progenitors.

Repeating FRBs

Repeating fast radio bursts (FRBs) are a subclass of FRBs characterized by multiple detections from the same sky location over time, distinguishing them from apparent one-off events and enabling deeper investigations into their emission mechanisms and environments. The first repeating source, FRB 121102, was initially detected in during the Arecibo PALFA survey, with subsequent observations revealing repeats starting in , confirming its recurring nature. As of 2021, over 1,652 bursts from FRB 121102 have been recorded, primarily through intensive monitoring with telescopes like FAST, exhibiting highly variable repetition rates that can reach up to 122 bursts per hour during active phases but typically range from 1 to 10 per hour on average. Bursts from repeating FRBs often display evolving morphologies, including downward frequency drifts—commonly termed the "sad trombone" effect—and progressive narrowing of pulse widths over successive emissions, suggesting dynamic effects within the source environment or . These also exhibit lower average fluences compared to non-repeating FRBs, with spectral fluences around 17 Jy ms versus 91 Jy ms for one-off sources, indicating potentially fainter intrinsic luminosities or beaming geometries. Approximately 2% of detected FRBs are known as of 2025, though population models suggest the true fraction could be higher if many low-activity sources remain undetected. The repeatable nature of these sources facilitates precise localization to host galaxies, allowing direct measurements and cosmological distance estimates. For instance, FRB 121102 is associated with a low-metallicity at z ≈ 0.193, located about 980 Mpc away, with its bursts originating from a compact, persistent radio source offset from the . Recent examples include FRB 20240209A, discovered in 2024 by CHIME and localized to the outskirts of a massive, quiescent at z ≈ 0.13, from which 22 bursts were detected between and 2024, hinting at origins in old stellar populations like globular clusters. Another notable case is FRB 20201124A, identified in 2020 and localized to a star-forming at z ≈ 0.097, featuring extreme rotation measures exceeding 1,000 rad m⁻², indicative of a highly magnetized circumsource medium.

Proposed Origins

Catastrophic Event Models

One prominent catastrophic model posits that non-repeating fast radio bursts (FRBs) arise from the mergers of binary neutron stars. In this scenario, the intense radio emission is generated during the merger process or immediately afterward, potentially through shocks in the dynamical ejecta forming a kilonova or from interactions involving the hypermassive neutron star remnant formed post-merger. The predicted event rate of such mergers, based on stellar evolution and gravitational wave constraints, is consistent with the observed volumetric rate of non-repeating FRBs, estimated at around 10^3–10^4 per gigaparsec^3 per year. However, these models face challenges in reproducing the high degrees of linear polarization observed in several FRBs, as the synchrotron or curvature radiation mechanisms typically predict a mix of linear and circular components that does not fully align with detections showing up to 100% linear polarization. Another set of models links non-repeating FRBs to radio emission associated with core-collapse or the afterglows of gamma-ray bursts (GRBs). Here, the burst is attributed to emission or reverse shock radiation when the supernova ejecta or GRB jet interacts with dense circumstellar material shed by a massive . These interactions can produce bright, short-lived radio flashes in environments with high densities, consistent with the extragalactic dispersion measures of FRBs. Yet, the timescales of FRBs conflict with the longer-duration radio afterglows predicted by standard forward shock models, which typically peak and decay over hours to days rather than exhibiting the observed impulsive profiles. Hypotheses involving s propose that FRBs could result from accretion episodes onto intermediate-mass s or, more speculatively, radio components of from evaporating s. In accretion models, tidal disruption events or extreme mass-ratio inspirals lead to relativistic outflows producing coherent radio emission analogous to mechanisms but in a catastrophic context. For evaporation, the final explosive phase releases a burst of particles, including radio photons, as the approaches the Planck mass. These models are disfavored because the radiated energies from processes are too low—on the order of 10^{10}–10^{12} erg—to account for the isotropic energies of 10^{40}–10^{42} erg observed in extragalactic FRBs, even at cosmological distances. Overall, catastrophic event models effectively explain the predominantly non-repeating statistics of FRBs and their high dispersion measures, which imply origins at extragalactic distances often exceeding hundreds of megaparsecs. These singular, destructive processes naturally preclude repetition, distinguishing them from persistent source scenarios. Despite this, no definitive multi-messenger associations have been confirmed by 2025, such as an FRB counterpart to the binary neutron star merger or any GRB-supernova event, limiting empirical validation.

Compact Object Scenarios

One prominent class of models posits that fast radio bursts (FRBs) originate from giant flares on young , which are highly magnetized with surface exceeding 10^{14} G. In these scenarios, the coherent radio emission arises from the interaction of flare-released energy with the magnetar's pair plasma or through fractures in the stellar crust, producing maser-like amplification that accounts for the observed high brightness temperatures exceeding 10^{35} K and levels up to 100%. This mechanism explains the short-duration, millisecond-scale pulses by invoking rapid energy release in a confined volume near the surface, where relativistic particles are accelerated along open lines. The magnetic field strength of these magnetars is inferred from their spin-down luminosity, which powers the flares and links directly to the FRB energetics. The spin-down luminosity is given by the formula Lsd=B2R6Ω46c3,L_{\rm sd} = \frac{B^2 R^6 \Omega^4}{6 c^3}, where BB is the surface , RR is the neutron star radius (typically ~10 km), Ω\Omega is the angular spin frequency, and cc is the ; for young magnetars producing FRBs with energies around 10^{40} erg, this yields B∼1015B \sim 10^{15} G, consistent with observed spin periods of milliseconds to seconds. Such fields enable the storage of immense , on the order of 10^{46} erg, which can be released in flares comparable to the Crab Nebula's 1969 giant flare but scaled to extragalactic distances. Alternative compact object scenarios involve interactions in pulsar binaries or collisions with small bodies. In binary systems, tidal synchronization between a pulsar and its companion can trigger periodic flares through magnetic reconnection, while asteroid or comet impacts on the neutron star surface may induce sudden plasma ejections, generating radio bursts via synchrotron maser emission in the magnetosphere. These models predict a range of burst morphologies, including the narrow temporal structures observed in some FRBs, without requiring cataclysmic destruction of the progenitor. Key evidence supporting magnetar origins includes the detection of FRB 200428, a 400 MHz radio burst co-located with a soft gamma repeater from the Galactic SGR 1935+2154, marking the first direct association between an FRB and a known . Recent 2025 studies have refined estimates of the Galactic magnetar population, suggesting a of ~10^{-3} yr^{-1} per , sufficient to account for the observed FRB rate of ~10^3 per day across the sky when extrapolated to young ages <10^4 years. These findings bolster the viability of flare-based models while highlighting the need for further multi-wavelength monitoring of nearby magnetars.

Hypotheses for Repeating Sources

Repeating fast radio bursts (FRBs) are thought to arise from long-lived central engines capable of producing multiple emissions over time, distinguishing them from one-off events. Hypotheses for these repeaters emphasize mechanisms that enable periodic or quasi-periodic activity, often involving neutron stars in dynamic configurations. These models build on the general framework of magnetar flares, where magnetic reconnection in the stellar magnetosphere generates coherent radio emission, but focus on repetition through sustained or modulated processes. One prominent hypothesis involves precessing neutron stars, where the wobbling motion of a highly magnetized neutron star leads to periodic flaring as its emission beam sweeps across the line of sight due to geometric beaming. This forced precession, potentially induced by a companion or internal torques, can explain observed periodicities in repeaters like FRB 180916.J0158+65, with periods on the order of days to weeks arising from the precession timescale. Similarly, binary systems offer orbital modulation as a repetition driver: in neutron star binaries, the orbital motion can periodically align the emission region with our viewing angle, or interactions between magnetospheres decades before merger can trigger repeated bursts through enhanced magnetic reconnection. These binary scenarios naturally account for clustered burst activity windows tied to orbital phases. Engine-driven models center on persistent magnetar activity in young systems, typically less than 10,000 years old, where the star's decaying magnetic field (around 10^{14}-10^{15} Gauss) powers recurrent flares. In these scenarios, variable twists in the magnetar's magnetic field lines, built up by differential rotation or crustal motions, lead to intermittent reconnection events that produce bursts, sustaining activity over months to years. Such young magnetars, born from core-collapse supernovae, provide a stable engine for prolific repeaters, with burst rates potentially exceeding hundreds per day during active phases. Environmental factors further enhance repetition by modulating the propagation or triggering of bursts through interactions with surrounding media. For instance, a young neutron star embedded in a supernova remnant can experience repeated shocks as its wind plows into the ionized ejecta, amplifying radio emission via synchrotron maser processes in the compressed magnetic fields. Similarly, in systems with a circumstellar medium—such as from a massive star companion—the dense, magnetized environment can scatter or reprocess bursts, leading to observable repetition influenced by the medium's density gradients. These interactions are particularly relevant for repeaters in star-forming regions, where the local plasma density (around 10^2-10^4 cm^{-3}) shapes burst profiles. Recent 2025 observations have refined these hypotheses, with the discovery of repeater FRB 20240209A localized to the outskirts (40 kpc offset) of a quiescent elliptical galaxy, challenging the assumption of young progenitors tied to active star formation. This source, detected with 22 bursts by CHIME/FRB, resides in an old stellar population (>10 billion years), suggesting repetition can occur in aged environments, possibly via long-lived magnetars or recycled neutron stars rather than nascent ones. Concurrently, four new studies analyzing localized repeaters have highlighted diverse origins, including associations with globular clusters, remnants, and binary companions, underscoring that no single mechanism dominates and that environmental diversity drives varied repetition patterns.

Notable Observations

Early Bursts (2007–2015)

The discovery of fast radio bursts began with the identification of the Lorimer burst (FRB 010724) in 2007, unearthed from archival data collected by the Parkes radio telescope in 2001 as part of a survey. This millisecond-duration event featured a dispersion measure (DM) of 375 pc cm⁻³, far exceeding typical Galactic values and indicating an extragalactic source at a cosmological distance, with an estimated of z ≈ 0.5 based on the intergalactic medium contribution to the DM. Reanalysis of the same Parkes dataset in 2011 revealed another burst, FRB 010621, with a lower DM of 162 pc cm⁻³, initially considered a candidate FRB but later argued to have a likely Galactic origin due to its proximity to the plane and local ionized gas contributions. These early detections, made through incoherent dedispersion searches in survey archives, established the basic observational signature of FRBs as bright, dispersed radio transients. Between 2010 and 2012, additional bursts emerged from the High Time Resolution Universe (HTRU) survey at Parkes, marking the first real-time population study. In 2013, four new FRBs were reported, including FRB 110220 (DM = 995 pc cm⁻³, detected on February 20, 2011) and FRB 121102 (DM = 557 pc cm⁻³, detected on November 2, 2012), both exhibiting high DMs consistent with extragalactic propagation through the interstellar and intergalactic media. FRB 121102 was later confirmed as the first repeating FRB in 2015 through targeted Arecibo observations, which detected multiple subsequent bursts from the same sky position, providing the first evidence for a non-catastrophic . These HTRU detections, processed via standard single-pulse searches, demonstrated a rate of approximately 10⁴ FRBs per sky per day above a fluence of 2 Jy ms, reinforcing their cosmological prevalence. From 2013 to 2015, the HTRU survey and related Parkes efforts yielded around 20 total FRB detections, expanding the sample and enabling initial statistical analyses. Notable among these was FRB 140514, discovered in real-time on , , during a follow-up campaign near prior FRB fields, with a DM of 273 pc cm⁻³ and linear polarization of about 20%, hinting at ordered magnetic fields in the source environment. Similarly, FRB 150418, detected on April 18, 2015, had a DM of 776 pc cm⁻³ and prompted multiwavelength follow-up that identified a tentative host galaxy at z ≈ 0.49, though the association with a fading radio transient was later attributed to an unrelated . These events, localized to within arcminute precision via Parkes' multibeam system, underscored the bursts' transient nature and broad sky distribution. The early bursts collectively established FRBs as an extragalactic phenomenon, with DMs implying origins beyond the and event rates suggesting a luminous, distant population. However, precise localizations remained elusive until the deployment of synthesis telescopes like ASKAP in later years, limiting host galaxy identifications during this period.

Key Repeating Sources

FRB 121102, the first identified repeating fast radio burst, has produced over 1,650 detected bursts since its initial discovery in , with extensive monitoring campaigns revealing clustered activity and diverse morphologies. Localized to sub-arcsecond precision within a low-metallicity at z=0.1924±0.0005z = 0.1924 \pm 0.0005, approximately 980 Mpc away, the source resides in a star-forming region offset from the galaxy's center, suggesting an association with young stellar populations. Its dispersion measure (DM) of about 557 pc cm⁻³ indicates a significant intergalactic contribution, consistent with the source's cosmological . A hallmark of FRB 121102 is its extreme Faraday measure (RM), which has shown dramatic over time, varying from approximately +4.3×104+4.3 \times 10^4 rad m⁻² in to peaks exceeding +1.2×105+1.2 \times 10^5 rad m⁻² by , with rapid changes on timescales of months. These fluctuations, among the largest observed for any FRB, imply a highly dynamic magneto-ionic environment near the source, possibly involving a young embedded in a dense or . No persistent radio counterpart has been firmly detected, though upper limits constrain any such emission to below 30 μJy at 1.5 GHz. FRB 20180916B, also known as FRB 180916.J0158+65, exhibits persistent repeating activity with over 150 bursts detected across frequencies from 110 MHz to 8 GHz, including periodic-like modulations on timescales of about 16 days. Localized to a (SDSS J015800.28+654253.0) at z=0.0337z = 0.0337, roughly 149 Mpc distant, the source lies near a bright Hα region, aligning with . Its relatively low DM of 349 pc cm⁻³ reflects the proximity, with host contributions estimated at 50–100 pc cm⁻³. The RM for FRB 20180916B is modest at around +100 rad m⁻², with minimal variation, indicating a less extreme local compared to more distant . Observations reveal frequency-dependent emission, with bursts detectable down to 110 MHz but showing and at lower frequencies, consistent with propagation through the host . A faint persistent radio source at 30 μJy has been tentatively associated, though its connection to the FRB remains uncertain. FRB 20200120E stands out as the nearest known repeating FRB, originating from a in the nearby galaxy M81 at a distance of about 3.6 Mpc. Precise milliarcsecond localization places the source just 2 pc from the cluster's optical center, an ancient stellar system aged 9–12 Gyr, challenging models requiring young progenitors. With a low DM of 87.8 pc cm⁻³, primarily from the and M81 halo, the bursts are exceptionally bright and narrow, with over 50 detected since 2020, often in short bursts or "storms." The location in an old suggests scenarios like a formed via – merger or an accreting , rather than a core-collapse , positioning it as a candidate for an aged or recycled driving the repetitions. Its RM is low at ~15 rad m⁻², with no significant evolution observed, reflecting the dilute of the cluster environment. No or gamma-ray counterparts have been detected, limiting high-energy emission to below 10^{42} erg s⁻¹. FRB 20201124A is one of the most prolific , with thousands of bursts detected, including rates exceeding 50 per hour during active periods, spanning a wide range up to 8 GHz. Localized to a star-forming (SDSS J050803.48+260338.0) at z=0.0977z = 0.0977, about 410 Mpc away, the source is offset from the nucleus in a region of moderate . Its DM of 413 pc cm⁻³ includes a host contribution of ~60 pc cm⁻³, typical for such environments. Notable for possessing the highest observed RM among FRBs, initially measured at ∼7.3×104\sim 7.3 \times 10^4 rad m⁻² and varying by up to 500 rad m⁻² on daily timescales, FRB 20201124A indicates a dense, magnetized circumsource medium, possibly a or wind nebula. imaging in 2023 revealed obscured in the host, with excesses suggesting dust-enshrouded activity near the FRB position, updated analyses in 2025 confirming no compact optical counterpart. A compact persistent radio source at ~100 μJy, co-located with the bursts, supports a young origin.

Recent Localizations and Bright Events (2018–2025)

Significant progress in localizing fast radio bursts (FRBs) began with the Australian Pathfinder (ASKAP), which enabled precise host identifications for non-repeating events. In September 2018, FRB 180924 was localized to within 4 kiloparsecs of the center of a luminous, massive early-type at z=0.3214, characterized by low and metal enrichment, marking the first such association for a one-off FRB. Similarly, FRB 190608, detected in June 2019, was pinpointed to a star-forming at z=0.1178, positioned in a dense along a spiral arm with a dispersion measure contribution of 94 ± 38 pc cm⁻³ from the host environment. These ASKAP localizations, achieved through interferometric mapping, highlighted the role of survey arrays in sub-arcsecond precision for host associations. Advancements in 2025 yielded the detection of the brightest FRB on record, FRB 20250316A (nicknamed RBFLOAT), observed on March 16 by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). This event released energy equivalent to four days of solar output in milliseconds, with a peak flux exceeding previous records and an estimated fluence of ~1.7 × 10³ Jy ms, allowing exceptional localization to the NGC 4141 at z ≈ 0.009 (~40 Mpc) using CHIME's telescopes. The precise positioning, refined in 2025, revealed the burst originating from within NGC 4141, providing insights into nearby FRB properties and intergalactic medium probing. Notable events from 2024 to 2025 further expanded the sample of localized FRBs. FRB 20240216, detected early in the year, contributed to ongoing surveys but lacked immediate host association details. In contrast, the repeating source FRB 20240209A, identified in February 2024 by CHIME and comprising 22 bursts, was localized in January 2025 to the outskirts of a quiescent approximately 2 billion light-years away (z ≈ 0.15), with an offset of 130,000 light-years from the center, challenging young stellar origin models. Additionally, observations in 2025 confirmed the host of the farthest known FRB, FRB 20240304B at z ≈ 2.15 (corresponding to 3 billion years after the ), revealing a low-mass, clumpy, star-forming as its origin. The diverse host environments of these localized FRBs—from actively star-forming spirals and massive ellipticals to ancient quiescent systems and high-redshift mergers—underscore a range of progenitor scenarios, including origins for repeaters in old galaxies, thereby challenging unified models that tie all FRBs to young magnetars in star-forming regions. This heterogeneity implies multiple formation channels, with implications for cosmic mapping and studies.

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