Fast radio burst

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In radio astronomy, a fast radio burst (FRB) is a high-energy astrophysical phenomenon of unknown origin manifested as a transient radio pulse lasting a few milliseconds on average. 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 Lorimer Burst. Many FRBs have since been found, including a repeating FRB.[1][2][3][4] Although the exact origin and cause is uncertain, they are almost definitely extragalactic.

When the FRBs are polarized, it indicates that they are emitted from a source contained within an extremely powerful magnetic field.[5] The origin of the FRBs has yet to be determined; proposals for its origin range from a rapidly rotating neutron star and a black hole, to extraterrestrial intelligence.[6][7]

The localization and characterization of the one known repeating source, FRB 121102, has revolutionized the understanding of the source class. FRB 121102 is identified with a galaxy at a distance of approximately 3 billion light years, well outside the Milky Way Galaxy, and embedded in an extreme environment.[8][9]

Nomenclature[edit]

Fast radio bursts are named by the date the signal was recorded, as "FRB YYMMDD". The first fast radio burst to be described, the Lorimer Burst FRB 010724, was identified in 2007 in archived data recorded by the Parkes Observatory on 24 July 2001. Since then, most known 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.[10]

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 outside the Milky Way. 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 a period of 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.

Frequencies and dispersion[edit]

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.[11] This results in a received signal that sweeps rapidly down in frequency, as longer wavelengths are delayed more.

Extragalactic origin[edit]

Fast radio bursts have pulse dispersion measurements which are much larger (> 100 pc cm−3[12]) than expected for a source inside the Milky Way;[13] and consistent with propagation through an ionized plasma,[11] and furthermore their distribution is isotropic (not especially coming from the galactic plane),[14]:fig 3 thus they are conjectured to be of extragalactic origin.

The interferometer UTMOST has also put a lower limit of 10,000 kilometers for the distance to the FRBs it has detected, supporting the case for an astronomical 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.[14]

Lorimer Burst[edit]

The first FRB, the Lorimer Burst FRB 010724, was discovered in 2007 when Duncan Lorimer assigned his student David Narkevic to look through archival data taken in 2001 by the Parkes radio dish in Australia.[15] Analysis of the survey data found a 30-jansky dispersed burst which occurred on 24 July 2001,[11] 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. The burst became known as the Lorimer Burst.[16] 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.[11] It is suggested that hundreds of similar events could occur every day and, if detected, could serve as cosmological probes.[17]

Further developments[edit]

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.[18] In 2015 perytons were shown to be generated when microwave oven doors were suddenly opened during a heating cycle, with emission generated by the magnetron.[19]

2011[edit]

In 2015, FRB 110523 was discovered in archival data from the Green Bank Telescope.[20] 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 is of extragalactic origin, possibly up to 6 billion light years away.[21][22]

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.[23]

FRB 121102[edit]

An observation in 2012 of a fast radio burst (FRB 121102)[4] 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.[24] The ten bursts have dispersion measures and sky positions consistent with the original burst FRB 121102, detected in 2012.[24] 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 only occur once, such as the explosion of a black hole or the collision between two neutron stars.[25] According to the scientists, the data support an origin in a young rotating neutron star (pulsar), or in a highly magnetized neutron star (magnetar),[24][25][26][27][4] or from highly magnetized pulsars travelling through asteroid belts,[28] or from an intermittent Roche lobe overflow in a neutron star-white dwarf binary.[29]

On 16 December 2016 six new FRBs were reported in the same direction (1 having been received on 13 Nov 2015, 4 on 19 Nov 2015, and 1 on 8 Dec 2015).[30]:Table 2 This is the only known instance in which these signals have been found twice in the same location in space. FRB 121102 is located at a minimum distance of about 1150 AU away from earth leaving out possibility of human-made source, and is almost certainly extragalactic in nature.[30]

As of January 2017, 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.[31][32][33][34][35]

On 26 August 2017, astronomers using data from the Green Bank Telescope detected additional 15 repeating FRBs coming from FRB 121102 at 5 to 8 G Hz. 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".[2][3][36] The waves are highly polarized, meaning "twisting" transverse waves, that could only have formed when passing through hot plasma with an extremely strong magnetic field.[37] FRB 121102's radio bursts are about 500 times more twisted (polarized) than those from any other FRB to date.[37] Since it is a repeating FRB source, it suggests that it does not come from some one-time cataclysmic event, so a hypothesis proposed 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,[37] or one embedded in a nebula.[38]

In April 2018, it was reported that FRB 121102 consisted of 21 bursts spannning one hour.[39] In September 2018, an additional 72 bursts spanning five hours had been detected using convolutional neural network.[40][41][42]

2013[edit]

In 2013, four bursts were identified that supported the likelihood of extragalactic sources.[43]

2014[edit]

In 2014, FRB 140514 was caught 'live' in 2014 and was found to be 21% (±7%) circularly polarised.[10]

Fast radio bursts discovered up until 2015 had dispersion measures that were close to multiples of 187.5 pc cm−3.[44] However subsequent observations do not fit this pattern.

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 "afterglow" of the flash, which took six days to fade.[45][46][47] 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.[48]

However, the origin of the burst was soon disputed,[49][50][51] and by April 2016 it was established that the emission instead originates from an active galactic nucleus that is powered by a supermassive black hole with dual jets blasting outward from the black hole.[52] It was also noted that what was thought to be an "afterglow", did not fade away as would be expected, meaning that what was observed was unassociated with the actual fast radio burst.[52]

2017[edit]

The upgraded Molonglo Observatory Synthesis Telescope (UTMOST), near Canberra (Australia), reports finding 3 more FRBs.[53] A 180-day 3 part survey in 2015 and 2016 found 3 FRBs at 843 MHz.[14] Each FRB located with a narrow elliptical 'beam'; The relatively narrow band 828–858 MHz gives a less precise DM.[14]

A short survey using part of ASKAP found one FRB in 3.4 days. FRB170107 was bright with a fluence of 58±6 Jy ms.[12][54]

The upcoming and unusual Canadian radio telescope called CHIME will also be used to detect "hundreds" of fast radio bursts as its secondary objective.[55][24]

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.[56]

2018[edit]

Three FRBs reported in March by Parkes Observatory in Australia. One (FRB 180309) had the highest signal to noise ratio yet seen of 411.[57][58]

FRB 180725A was reported (by CHIME) as the first detection of a FRB under 700 MHz – as low as 580 MHz.[59][60]

Origin hypotheses[edit]

Because of the isolated nature of the observed phenomenon, the nature of the source remains speculative. As of 2016, there is no generally accepted explanation. The source is estimated to be no larger than a few hundred kilometers in size because of causality (the bursts last for only a few milliseconds). If the bursts come from cosmological distances, their sources must be very bright.[61]

One possible explanation would be a collision between very dense objects like merging black holes or neutron stars.[15] It has been suggested that there is a connection to gamma-ray bursts.[62][63] Some have speculated that these signals might be artificial in origin, that they may be signs of extraterrestrial intelligence.[64][65][66]

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.[67][68] In 2015 three studies supported the magnetar hypothesis.[20][69][70][71]

Especially energetic supernova could be the source of these bursts.[72] Blitzars were proposed in 2013 as an explanation.[61] In 2014 it was suggested that following dark matter-induced collapse of pulsars,[73] the resulting expulsion of the pulsar magnetospheres could be the source of fast radio bursts.[74] In 2015 it was suggested that FRBs are caused by explosive decays of axion miniclusters.[75] Another exotic possible source are cosmic strings that produced these burst as they interacted with the plasma that permeated the early Universe.[72] 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.[76][77] 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.[15][78] 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.[79]

Repeated bursts of FRB 121102 have initiated multiple origin hypotheses.[80] 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, variable intensity profiles).[81]

List of bursts[edit]

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[82] 2001-06-21 13:02:10.795 18h 52m −08° 29′ 746 7.8 0.4
FRB 010724[11] 2001-07-24 19:50:01.63 01h 18m −75° 12′ 375 4.6 30 "Lorimer Burst"
FRB 011025[83] 2001-10-25 00:29:13.23 19h 07m −40° 37′ 790 9.4 0.3
FRB 090625[84] 2009-06-25 21:53:52.85 03h 07m −29° 55′ 899.6 <1.9 >2.2
FRB 110220[43] 2011-02-20 01:55:48.957 22h 34m −12° 24′ 944.38 5.6 1.3
FRB 110523 [20][21][22] 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[43] 2011-06-27 21:33:17.474 21h 03m −44° 44′ 723.0 <1.4 0.4
FRB 110703[43] 2011-07-03 18:59:40.591 23h 30m −02° 52′ 1103.6 <4.3 0.5
FRB 120127[43] 2012-01-27 08:11:21.723 23h 15m −18° 25′ 553.3 <1.1 0.5
FRB 121002[85] 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[84] 2012-10-02 13:09:18.50 18h 14m −85° 11′ 1629.18 <0.3 >2.3
FRB 121102[86] 2012-11-02 06:35:53.244 05h 32m +33° 05′ 557 3.0 0.4 by Arecibo radio telescope

Repeating bursts,[2][3][30][87] very polarized.

FRB 130626[84] 2013-06-26 14:56:00.06 16h 27m −07° 27′ 952.4 <0.12 >1.5
FRB 130628[84] 2013-06-28 03:58:00.02 09h 03m +03° 26′ 469.88 <0.05 >1.2
FRB 130729[84] 2013-07-29 09:01:52.64 13h 41m −05° 59′ 861 <4 >3.5
FRB 131104[88] 2013-11-04 18:04:01.2 06h 44m −51° 17′ 779.0 <0.64 1.12 'near' Carina Dwarf Spheroidal Galaxy
FRB 140514[89] 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[90][91] 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.[90]
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.[49][50][51][52]
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[26][27]
and 1 on 13 Nov 2015, 4 on 19 Nov 2015, and 1 on 8 Dec 2015[30]
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[92] 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,[92] 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[14] 2016-03-17 09:00:36.530 07:53:47 −29:36:31 1165(±11) 21 >3.0 UTMOST, Decl ± 1.5°[14]:Table A1
FRB 160410[14] 2016-04-10 08:33:39.680 08:41:25 +06:05:05 278(±3) 4 >7.0 UTMOST, Decl ± 1.5°[14]:Table A1
FRB 160608[14] 2016-06-08 03:53:01.088 07:36:42 −40:47:52 682(±7) 9 >4.3 UTMOST, Decl ± 1.5°[14]:Table A1
FRB 170107[12] 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[12]
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.[2]
FRB 170827[93] 2017-08-27 16:20:18 00h 49m 18.66s −65° 33′ 02.3″ 176.4 0.395 low DM
FRB 170922[94] 2017-09-22 11:23:33.4 21h 29m 50.61s −07° 59′ 40.49″ 1111 26 extreme scattering (long pulse)
FRB 171209[95] 2017-12-09 20:34:23.5 15h 50m 25s −46° 10′ 20″ 1458 2.5 2.3
FRB 180301[96] 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[97] 2018-03-09 02:49:32.99 21h 24m 43.8s −33° 58′ 44.5″ 263.47 0.576 12
FRB 180311[98] 2018-03-11 04:11:54.80 21h 31m 33.42s −57° 44′ 26.7″ 1575.6 12 2.4
FRB 180725A[60][99] 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.

FRBs are also cataloged at frbcat.[100]

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