FRB Theory Wiki - User contributions [en]

Tiny EM Explosions

2018-10-11T11:30:48Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Other
|Progenitor = Tiny EM Explosions
|Type = Both
|EnergyMechanism = Thin shell interactions
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = Unlikely observable
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1703.00393, http://adsabs.harvard.edu/abs/2017ApJ...844...65T
|Comments = None
}}

== Model Description ==

The collision of two relativistic macroscopic dipoles that form around the time of cosmic electroweak symmetry-breaking could cause a tiny explosion. Tiny electromagnetic explosions occur when the initial wavelength of the explosion is narrower than the wavelength of the radiation observed so the energy travels outwards in a very thin shell, and the surrounding charged particles are deflected (as opposed to reflected) by the magnetic field embedded in the expanding shell.

To retain the supporting electric field for cosmological timescales, these field structures must be superconducting, and are thus dubbed large superconducting dipoles (LSD) - the term "Large" is relative, and is used because the dipoles are macroscopic. The expanding relativistic magnetized shell from the explosion couples efficiently to a low-frequency, strong, superluminal EM wave in the surrounding plasma, allowing the emission to escape. Three emission mechanisms are possible: the reflection of an ambient static magnetic field by the conducting surface of the shell; direct linear conversion of the magnetic field in the shell; and the excitation of an EM wave if the surface of the shell becomes corrugated via the reconnection of the ejected magnetic field with the ambient magnetic field. The deceleration of the magnetic shell causes a higher frequency radio pulse and the thermal part of the explosion radiates Gamma-rays, however the latter are not expected to be detectable. The model accounts for repeating and non-repeating FRBs and for their observed differences in linear polarizations and RMs - the hydromagnetic drag on LSDs is weak in the ISM, and strong in high - density environments. As such, a slowly accreting SMBH may capture LSDs and group them in gravitationally bound cusps, within which the LSDs collide and create repeating FRBs. Here the high density plasma accounts for the high linear polarization and high RM observed in FRB 121102. The opposite is true for LSDs far from the SMBH; where the observed RM is low and signals are non-repeating, such as in FRB 150215, collisions are expected to take place in dark matter halos of galaxies.

== Observational Constraints ==

--

Stellar Coronae

2018-10-11T11:30:18Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Void
|Progenitor = Stellar Corona
|Type = Both
|EnergyMechanism = N/A
|EmissionMechanism = N/A
|LFRadioCounterpart = N/A
|HFRadioCounterpart = N/A
|MicrowaveCounterpart = N/A
|THzCounterpart = N/A
|OIRCounterpart = N/A
|XrayCounterpart = N/A
|GammarayCounterpart = N/A
|GWCounterpart = N/A
|NeutrinoCounterpart = N/A
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1310.2419, http://adsabs.harvard.edu/abs/2015MNRAS.454.2183M
|Comments = None
}}

== Model Description ==

One of the last surviving theories for FRBs of Galactic origins was flare stars. The theory was seemed fitting because dwarf stars have been observed to produce bursts of coherent radiation on short timescales ($< 5$ ms) and have been observed within FRB fields. A cyclotron maser in the lower part of the stellar corona could produce a flare consistent with FRB observations; the large DM and pulse smearing could be attributed to the corona plasma. Free-free absorption that occurs in the corona, however, presents a problem: a radio signal from the lower corona with the required DM may be unobservable unless the corona is infeasibly extended or hot. Further, the plasma density required for the DM is arguably too high to produce the frequency dependence on the pulse arrival times observed for FRBs. In defence of the theory, observations by are given that show high flare temperatures capable of mitigating significant free-free absorption. Further, if frequency drifts occur in flares (as observed in), the measured dispersion relationship for FRBs may be possible. Doubt is then cast on the theory again when it is shown that the brightness temperature of FRBs could not escape plasma as dense as the DM demands.

== Observational Constraints ==

--

SS Crust

2018-10-11T11:29:49Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Collapse
|Progenitor = Strange Star Crust
|Type = Single
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1805.04448
|Comments = None
}}

== Model Description ==

Charge separation in strange quark stars can induce large electric fields emanating from their core, which, through polarization of nearby surrounding hadrons, can lead to the formation of a hadronic crust around the star. Should the strange star accrete a sufficient amount of matter, the hadrons in the crust will tunnel across the Coulomb barrier, to the strange quark matter (SQM) core, where they too are converted to SQM. This accretion heats the core, hastens the tunnelling process, and eventually and inevitably leads to the collapse of the hadronic crust. As it collapses, the magnetic field lines associated with the crust are dragged with the matter, causing a disruption in the field lines of the SS core. Thus, via magnetic reconnection, electron-positron pairs are accelerated to ultra-relativistic speeds along the magnetic field lines, generating a thin shell of relativistic particles that accelerate around the bare SQM core to emit curvature radiation. Even a small portion of the magnetic energy held in the polar cap region of the SS core would be sufficient to power an FRB and the timescales of collapse are consistent with observations.

== Observational Constraints ==

--

Pulsar Wind Bubble

2018-10-11T11:28:18Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = SNR (Pulsars)
|Progenitor = Pulsar Wind Bubble (NS and MWD)
|Type = Single
|EnergyMechanism = --
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = ULXs
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2017MNRAS.467.3542M
|Comments = Emission from the PWN as it expands outwards might be detected in the NS scenario. A SN a few years prior to the FRB may be observed for either body.
}}

== Model Description ==
Consider a pulsar (NS or magnetic WD, hereafter MWD) within a nebula. The dissipation of spin energy drives a wind of relativistic electron-positron plasma--a pulsar wind nebula (PWN)--observable as a shell around the NS. Where the plasma wind ceases is called the termination shock. Here the plasma decelerates to sub-relativistic speeds and forms a wind bubble around the pulsar. A subsequent outburst, possibly triggered by pulsar spin-down or by magnetic dissipation in the magnetosphere, will rapidly decelerate when it impacts the PWN, triggering a GRB. Energy that is not radiated away by the explosion itself travels outwards at a relativistic speed, causing a highly relativistic shock wave to propagates forward into space. Synchrotron emission is generated, however the coherence mechanism to generate FRBs at this point is unknown. A synchrotron maser might result from the coherently reflected particles in the shock front, but for NSs and magnetic MWDs the frequency is likely too low to be consistent with FRBs. A reverse shock wave may give rise to afterglow, however both this afterglow and the GRB formed at the shock front are not expected to be observable.

== Observational Constraints ==

--

NS-NS Merger (Mag. Braking)

2018-10-11T11:27:06Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Merger
|Progenitor = NS-NS
|Type = Single
|EnergyMechanism = Mag. braking
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Kilonova
|XrayCounterpart = Afterglow
|GammarayCounterpart = sGRB <br/> if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2013PASJ...65L..12T
|Comments =
}}

== Model Description ==

Consider the merging of two differentially rotating NSs into a uniformly rotating hypermassive NS. Upon coalescence, the merger spins down and magnetic braking generates coherent radiation. Since the merger rate of NSs is consistent with the expected FRB rate, this model implies that a large fraction of NS mergers must produce FRBs. Significant mass ejections are likely to occur during the merger process, which render FRBs unable to penetrate the ejecta. There is a 1 ms time frame after the maximum rotation speed of the merger is reached and before the release of dynamical ejecta, during which the transmission of a single FRB is possible.

== Observational Constraints ==

--

NS to KNBH

2018-10-11T11:26:39Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Collapse
|Progenitor = NS to KNBH
|Type = Single
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1307.1409, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1603.05509
|Comments = Possible X-ray afterglow and a short/long GRB created in NS birth prior to the FRB.
}}

== Model Description ==

Upon the collapse of a supramassive NS into a NKBH, an event horizon will likely form before most of the mass and radiation can escape. By the no-hair theorem, magnetic fields are forbidden from piercing the event horizon, and so the magnetosphere will be left behind. Alternatively, if a NS collapses into a metastable KNBH, its electric discharge can cause the magnetosphere to be shed. Violent magnetic reconnection outside the horizon would then induce a strong magnetic shock wave that moves through the remaining plasma at the speed of light, resulting in a single FRB.

== Observational Constraints ==

--

Neutral Cosmic Strings

2018-10-11T11:25:43Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Void
|Progenitor = Neutral Cosmic Strings
|Type = Single
|EnergyMechanism = N/A
|EmissionMechanism = N/A
|LFRadioCounterpart = N/A
|HFRadioCounterpart = N/A
|MicrowaveCounterpart = N/A
|THzCounterpart = N/A
|OIRCounterpart = N/A
|XrayCounterpart = N/A
|GammarayCounterpart = N/A
|GWCounterpart = N/A
|NeutrinoCounterpart = N/A
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1707.02397
|Comments = None
}}

== Model Description ==

Nambu-Goto (infinitely thin, idealised) cosmic strings generically form cusps---portions of the string which fold back onto themselves and move at the speed of light. The cusps decay to form a beam of coherent radiation, where the emission can ostensibly be of any energy and frequency range. As such, cusp decay has been considered as an FRB origin. The event rate, timescale, and flux are shown to be consistent with FRB data, however the relativistic effects on the cusp shape where not originally considered. By taking this into account, the consistency of the theory breaks down.

== Observational Constraints ==

--

DSR in Galaxies

2018-10-11T11:24:56Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Other
|Progenitor = Dicke's Superradiance in Galaxies
|Type = Both
|EnergyMechanism = Dicke's Superradiance
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2018MNRAS.475..514H
|Comments = --
}}

== Model Description ==

Postulated in 1953 and first detected in 1973, Dicke's Superradiance (DSR) has been invoked as one of the few “microphysical” FRB models. The aim is to explain FRBs using the atomic interactions in galaxies. DSR can occur in astrophysical settings, provided: the collection of atoms is inverted; the velocity coherence is high; and the non-coherent relaxation mechanisms occur on a timescale larger than the delay time. If one models the ISM as a cylinder of atoms, the predicted DSR emission power and timescale can fit FRB data. This model is additionally appealing since the DSR mechanism can adapt to a wide variety of FRB behaviour, and proposes no new entities/physics. Indeed, the DMs associated with FRBs fits well with the ISM required for DSR to occur. DSR also presents a mechanism through which a repeater can be explained. If a collection of molecules has DSR triggered at the same time, the intrinsic variation in the DSR timescale and time delay would give the observation of bursts at different times. The variation is because the time delay is an expectation value, and the collection of molecules being ionised at the same time is due to the entanglement, which also causes a differential in emission time. This process can happen repeatedly as population inversion will be non-inverted but swiftly restored via the ISM, which will drive more FRB pulses, and so on. The flux distribution of such a setup can be matched to FRB 121102.

== Observational Constraints ==

--

Annihilating Mini BHs

2018-10-11T11:24:19Z

Jake Gordin: /* Observational Constraints */

{{FRBTableTemplate
|Category = Void
|Progenitor = Annihilating Mini BHs
|Type = Single
|EnergyMechanism = N/A
|EmissionMechanism = N/A
|LFRadioCounterpart = N/A
|HFRadioCounterpart = N/A
|MicrowaveCounterpart = N/A
|THzCounterpart = N/A
|OIRCounterpart = N/A
|XrayCounterpart = N/A
|GammarayCounterpart = N/A
|GWCounterpart = N/A
|NeutrinoCounterpart = N/A
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1206.4135
|Comments = None
}}

== Model Description ==

When a BH evaporates to some critical mass, a fireball of $e^+_-$ pairs can be created. The relativistic pairs expand into the magnetic field of the surrounding ISM, which could produce emission consistent with an FRB. The inferred distance for the Lorimer burst in this scenario, however, is calculated to be <20 kpc. This would place the source within our galaxy, and thus the theory is rendered void.

== Observational Constraints ==

--

MWN Shock (Clustered Flares)

2018-10-11T11:21:34Z

Jake Gordin: /* Model Description */

{{FRBTableTemplate
|Category = SNR (Magnetars)
|Progenitor = MWD Shock (Clustered Flares)
|Type = Repeat
|EnergyMechanism = Maser
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Afterglow
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Maybe
|XrayCounterpart = --
|GammarayCounterpart = Low energy gamma-rays, sGRB if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2017ApJ...843L..26B
|Comments = None
}}

== Model Description ==

A hyper-active magnetar is proposed to produce multiple millisecond flares at different energies close to the magnetar. Such a magnetar is young with a hyper-energetic SN shell and an ultra-fast rotation period. The multiple flares interact to form a series of shocks before reaching the MWN. The FRBs arise from a synchrotron maser formed by gyrating particles at the shock front. Flares in this scenario arise from ambipolar diffusion in the magnetar core; a process which is then enhanced by the strong magnetic fields associated with the high magnetar spin. The flares will therefore be significantly more energetic than those of usual magnetars. Less active magnetars can emit FRBs by the same mechanism, but these will be non-repeating. Since repeating FRBs call for rarer magnetars, their event rate is expected to be lower.

The flares from young magnetars are consistent with the properties of the Lorimer burst. FRB 110523 is in-keeping with magnetar flares. Based on the observations of SGR 1806-20, the energy and number of particles N ~ 10^{52} in FRB 121102 are found to be consistent with magnetar ejecta, and thus it is arguably more likely to be powered by magnetic fields than rotational energy. The host galaxy of FRB 121102 supports the predicted long-duration gamma-ray bursts and hydrogen-poor (SLSNe I) formed in the birth of millisecond magnetars. The variable radio source associated with FRB 121102 is consistent with the giant flare theory, too: it may be emission directly from the MWN, the shock interaction between the flare and the MWN, or afterglow from an off-axis LGRB (such that only the afterglow is observed). Note that for the flare model to be consistent, this emission is expected to decay by ~ 10 within the next few years. Constraints on the large, decreasing RM and required radio transparency for FRB 121102 is consistent with a young magnetar with an expanding magnetized electron-ion nebula, akin to those associated with SLSNe. Such a nebula can also account for the observed properties of the variable counterpart associated with FRB 121102.

The flare theory has been met with various criticisms. The upper limit on RMs of giant flares is 4 orders of magnitude lower than that observed for FRB 121102. The magnetar wind therefore may not have a large enough magnetic field to account for the RM without a massive BH in its vicinity. Should this be the case, the chances of having a young magnetar near a massive BH is far lower than having a regular magnetar. The polarization percentage of pulsar emission has been observed to generally increase with decreasing observing frequency, with some pulsars also having a constant linear polarization percentage below some critical frequency. The variation of RM is also expected to increase as the distance to the pulsar increases. To be consistent with ~ 100 linear polarization and varying RM (~ 10 over 7 months) of FRB 121102, FRBs must originate some distance from the surface of magnetar. This presents a conflict: the enormous brightness temperatures of FRB emission requires strong magnetic fields close to the magnetar surface. The age of the magnetar must also fall within a "Goldilocks Zone": for the appropriate energy budget, the magnetar cannot be too old, but to penetrate ejecta and avoid DM variation it cannot be too young.

== Observational Constraints ==

From these models, high-energy GRBs, and possibly a coincident optical flash from the explosion are predicted. Flaring from the reverse shock could lead to additional (lower-energy) gamma-ray emission, and the interaction between the GRB and the ejecta could lead to broadband afterglow emission lasting days to weeks. The quasi-steady nebular emission of the MWN itself may be difficult to detect. X-rays are able to penetrate the ejecta, but only on 100 year timescales, and are therefore unlikely to be detected. A testable signature is that the persistent variable radio source associated with FRB 121102 is predicted to decay by ~ 10 within the next few years.

A magnetar that emits bursts at irregular intervals is a SGR. Although SGRs and FRBs share similar properties, such as: characteristic timescales, low duty factors and repetition, there is a crucial difference. SGRs are observed to be entirely thermal with frequencies above the X-ray range, whereas FRBs are observed in radio frequencies. Another possible inconsistency is that the Parkes Telescope failed to detect an FRB counterpart to the giant flare of SGR 1806-20: only one of the fifteen FRBs analyzed has a gamma-ray fluence ratio consistent with the SGR. The bursts of FRB 121102 have varied spectral characteristics, which suggests the observed fluence ratio may vary significantly between different magnetars and between bursts from the same magnetar. FRBs therefore may not be observable for all SGRs, which would explain the lack of a detectable radio counterpart in SGR 1806-20. Searches for GRBs associated with FRBs (repeating and non-repeating) with the Fermi Large Area Telescope (LAT) have not revealed any results, nor have placed any stringent constraints on the magnetar model.

MWN Shock (Clustered Flares)

2018-10-11T11:19:21Z

Jake Gordin:

{{FRBTableTemplate
|Category = SNR (Magnetars)
|Progenitor = MWD Shock (Clustered Flares)
|Type = Repeat
|EnergyMechanism = Maser
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Afterglow
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Maybe
|XrayCounterpart = --
|GammarayCounterpart = Low energy gamma-rays, sGRB if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2017ApJ...843L..26B
|Comments = None
}}

== Model Description ==

A hyper-active magnetar is proposed to produce multiple millisecond flares at different energies close to the magnetar. Such a magnetar is young with a hyper-energetic SN shell and an ultra-fast rotation period. The multiple flares interact to form a series of shocks before reaching the MWN. The FRBs arise from a synchrotron maser formed by gyrating particles at the shock front. Flares in this scenario arise from ambipolar diffusion in the magnetar core; a process which is then enhanced by the strong magnetic fields associated with the high magnetar spin. The flares will therefore be significantly more energetic than those of usual magnetars. Less active magnetars can emit FRBs by the same mechanism, but these will be non-repeating. Since repeating FRBs call for rarer magnetars, their event rate is expected to be lower.

The flares from young magnetars are consistent with the properties of the Lorimer burst. FRB 110523 is in-keeping with magnetar flares. Based on the observations of SGR 1806-20, the energy and number of particles N ~ 10^{52} in FRB 121102 are found to be consistent with magnetar ejecta, and thus it is arguably more likely to be powered by magnetic fields than rotational energy. The host galaxy of FRB 121102 supports the predicted long-duration $\gamma$-ray bursts (\acrshort{lgrb}) and hydrogen-poor \acrlong{slsn}(SLSNe I) formed in the birth of millisecond magnetars. The variable radio source associated with FRB 121102 is consistent with the giant flare theory, too: it may be emission directly from the MWN, the shock interaction between the flare and the MWN, or afterglow from an off-axis LGRB (such that only the afterglow is observed). Note that for the flare model to be consistent, this emission is expected to decay by $\sim 10 \%$ within the next few years. Constraints on the large, decreasing RM and required radio transparency for FRB 121102 is consistent with a young $\gtrsim 30-100$ year old magnetar with an expanding magnetized electron-ion nebula, akin to those associated with SLSNe. Such a nebula can also account for the observed properties of the variable counterpart associated with FRB 121102.

The flare theory has been met with various criticisms. The upper limit on RMs of giant flares is 4 orders of magnitude lower than that observed for FRB 121102. The magnetar wind therefore may not have a large enough magnetic field to account for the RM without a massive BH in its vicinity. Should this be the case, the chances of having a young magnetar near a massive BH is far lower than having a regular magnetar. The polarization percentage of pulsar emission has been observed to generally increase with decreasing observing frequency, with some pulsars also having a constant linear polarization percentage below some critical frequency. The variation of RM is also expected to increase as the distance to the pulsar increases. To be consistent with ~ 100 linear polarization and varying RM (~ 10 over 7 months) of FRB 121102, FRBs must originate some distance from the surface of magnetar. This presents a conflict: the enormous brightness temperatures of FRB emission requires strong magnetic fields close to the magnetar surface. The age of the magnetar must also fall within a ``Goldilocks Zone'': for the appropriate energy budget, the magnetar cannot be too old, but to penetrate ejecta and avoid DM variation it cannot be too young.

== Observational Constraints ==

From these models, high-energy GRBs, and possibly a coincident optical flash from the explosion are predicted. Flaring from the reverse shock could lead to additional (lower-energy) gamma-ray emission, and the interaction between the GRB and the ejecta could lead to broadband afterglow emission lasting days to weeks. The quasi-steady nebular emission of the MWN itself may be difficult to detect. X-rays are able to penetrate the ejecta, but only on 100 year timescales, and are therefore unlikely to be detected. A testable signature is that the persistent variable radio source associated with FRB 121102 is predicted to decay by ~ 10 within the next few years.

A magnetar that emits bursts at irregular intervals is a SGR. Although SGRs and FRBs share similar properties, such as: characteristic timescales, low duty factors and repetition, there is a crucial difference. SGRs are observed to be entirely thermal with frequencies above the X-ray range, whereas FRBs are observed in radio frequencies. Another possible inconsistency is that the Parkes Telescope failed to detect an FRB counterpart to the giant flare of SGR 1806-20: only one of the fifteen FRBs analyzed has a gamma-ray fluence ratio consistent with the SGR. The bursts of FRB 121102 have varied spectral characteristics, which suggests the observed fluence ratio may vary significantly between different magnetars and between bursts from the same magnetar. FRBs therefore may not be observable for all SGRs, which would explain the lack of a detectable radio counterpart in SGR 1806-20. Searches for GRBs associated with FRBs (repeating and non-repeating) with the Fermi Large Area Telescope (LAT) have not revealed any results, nor have placed any stringent constraints on the magnetar model.

Jet-Caviton

2018-10-11T10:52:48Z

Jake Gordin:

{{FRBTableTemplate
|Category = AGN
|Progenitor = Jet-Caviton Interaction
|Type = Both
|EnergyMechanism = Electron scattering
|EmissionMechanism = Bremsst.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = Possible GRB
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2016PhRvD..93b3001R, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1704.08097
|Comments = None
}}

== Model Description ==

A hot accretion disk forms as matter is captured and spirals into a moderately sized BH. Some of the in-falling gas and dust is confined to the poles and ejected in two relativistic jets. Hot gas clouds of varying densities surround the BH, forming a toroid that extends a few parsecs from the BH. As the AGN jet interacts with the clouds, it becomes narrowly collimated. The relativistic e+/e− beam encounters material at the center of the host galaxy, and strong turbulence is produced by plasma instabilities. The total pressure and the ponderomotive force (experienced by a charged particle in an oscillating electric field) cause electrons and ions to separate. These regions, called cavitons, are filled by a strong electrostatic field. Electrons from the beam that pass through the caviton are coherently scattered and emit strongly beamed Bremsstrahlung radiation in pulses. FRBs may be single or repeating.

== Observational Constraints ==

Radiation might be linearly polarized if there is a local magnetic field, however the 100% polarization degree of FRB 121102 would be difficult to account for in this scenario. The persistent scintillating radio emission from the AGN is an expected counterpart, which agrees with observations of FRB 121102.

Jet-Caviton

2018-10-11T10:51:39Z

Jake Gordin: /* Model Description */

{{FRBTableTemplate
|Category = AGN
|Progenitor = Jet-Caviton Interaction
|Type = Both
|EnergyMechanism = Electron scattering
|EmissionMechanism = Bremsst.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = Possible GRB
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2016PhRvD..93b3001R, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1704.08097
|Comments = None
}}

== Model Description ==

Let us first discuss the formation of AGN jets. Consider a hot accretion disk formed as matter is captured and spirals into a moderately sized BH. Some of the in-falling gas and dust is confined to the poles and ejected in two relativistic jets. Hot gas clouds of varying densities surround the BH, forming a toroid that extends a few parsecs from the BH. As the AGN jet interacts with the clouds, it becomes narrowly collimated. The relativistic e+/e− beam encounters material at the center of the host galaxy, and strong turbulence is produced by plasma instabilities. The total pressure and the ponderomotive force (experienced by a charged particle in an oscillating electric field) cause electrons and ions to separate. These regions, called cavitons, are filled by a strong electrostatic field. Electrons from the beam that pass through the caviton are coherently scattered and emit strongly beamed Bremsstrahlung radiation in pulses. FRBs may be single or repeating.

== Observational Constraints ==

Radiation might be linearly polarized if there is a local magnetic field, however the 100% polarization degree of FRB 121102 would be difficult to account for in this scenario. The persistent scintillating radio emission from the AGN is an expected counterpart, which agrees with observations of FRB 121102.

Axion Star and NS

2018-10-11T10:46:25Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collision / Interaction
|Progenitor = Axion Star and NS
|Type = Single
|EnergyMechanism = Electron oscillation
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1412.7825, http://adsabs.harvard.edu/abs/2015PhRvD..91b3008I, http://adsabs.harvard.edu/abs/2016PhRvD..94j3004R
|Comments = None
}}

== Model Description ==

In the presence of a magnetic field, axions have been shown to produce radiation by generating an oscillating electric field, causing nearby electrons to radiate coherently. The radiation produced when an axion star collides with a NS has been shown to be consistent with non-repeating FRBs. As the axion star moves through the magnetosphere of the neutron star, a time-dependent electric dipole moment is induced, forcing free electrons above the surface of the NS to oscillate harmonically. This generates coherent radiation with a frequency determined by the axion mass an effect which could be even larger, if one considers the electric dipole moment induced in the neutrons interior to the NS. The theory is shown to be robust to the effects of tidal disruption, however this has been disputed.

== Observational Constraints ==

A defining feature of the model is that the intrinsic FRB emission frequency is finite, and the observed spectral broadening is due to thermal Doppler effects. The emission is also expected to be circularly polarized. A two-component profile may be observed if the axion star collides with a binary NS system. No counterparts are expected. The significant broadening of FRBs, their linear polarization and the large range of frequencies at which FRBs have been detected is at odds with these theories.

Axion Minicluster and NS

2018-10-11T10:40:03Z

Jake Gordin: /* Observational Constraints */

Axion Minicluster and NS

2018-10-11T10:39:49Z

Jake Gordin:

AGN-SS

2018-10-11T10:33:22Z

Jake Gordin:

{{FRBTableTemplate
|Category = AGN
|Progenitor = AGN-Strange Star Interaction
|Type = Repeat
|EnergyMechanism = Electron oscillation
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Thermal
|XrayCounterpart = --
|GammarayCounterpart = Yes
|GWCounterpart = Yes
|NeutrinoCounterpart = Yes
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1709.00185
|Comments = Neutrinos from preceding SN and from collapse to BH. GW from collapse and persistent GWs from SS.
}}

== Model Description ==

A strange quark star (SS) is made up of approximately the same number of up, down, and strange quarks, with a small number of electrons distributed across the star's surface. Should an AGN wind interact with a SS, it can induce torsional oscillation of the electron layer relative to the positively charged SS, which can emit high luminosity GHz radio waves, consistent with FRBs. The sporadic nature of AGN wind would induce a repeating FRB.

== Observational Constraints ==

Persistent gravitational waves are expected from the SS due to its r-mode instability. If the SS is the result of a spinning down magnetar, neutrinos and a GW could be released when the magnetar collapses, however this emission need not be close in time to the interaction of the SS with the AGN, making it difficult to draw any associations.

AGN-SS

2018-10-11T10:32:16Z

Jake Gordin:

{{FRBTableTemplate
|Category = AGN
|Progenitor = AGN-Strange Star Interaction
|Type = Repeat
|EnergyMechanism = Electron oscillation
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Thermal
|XrayCounterpart = --
|GammarayCounterpart = Yes
|GWCounterpart = Yes
|NeutrinoCounterpart = Yes
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1709.00185
|Comments = Neutrinos from preceding SN and from collapse to BH. GW from collapse and persistent GWs from SS.
}}

== Model Description ==

A strange quark star (SS) is made up of approximately the same number of up, down, and strange quarks, with a small number of electrons distributed across the star's surface. Should an AGN wind interact with a SS, it can induce torsional oscillation of the electron layer relative to the positively charged SS, which can emit high luminosity GHz radio waves \cite{Mannarelli:2014jfa}, consistent with FRBs \cite{DasGupta:2017uac}. The sporadic nature of AGN wind would induce a repeating FRB. Persistent gravitational waves are expected from the SS due to its r-mode instability \cite{Andersson:2001ev}. If the SS is the result of a spinning down magnetar, neutrinos and a GW could be released when the magnetar collapses, however this emission need not be close in time to the interaction of the SS with the AGN, making it difficult to draw any associations.

== Observational Constraints ==

Superconducting Cosmic Strings

2018-10-11T10:04:19Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = Superconducting Cosmic Strings
|Type = Single
|EnergyMechanism = Cusp decay
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = GRB <br/> if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = Yes
|References = http://adsabs.harvard.edu/abs/2015AASP....5...43Z, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1807.01976, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:0802.0711

|Comments = High energy cosmic rays are also expected.
}}

== Model Description ==

To be filled in with updated draft

== Observational Constraints ==

To be filled in with updated draft

Superconducting Cosmic Strings

2018-10-11T10:03:58Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = Superconducting Cosmic Strings
|Type = Single
|EnergyMechanism = Cusp decay
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = GRB <br/> if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = Yes
|References = http://adsabs.harvard.edu/abs/2015AASP....5...43Z to main paper, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1807.01976, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:0802.0711

|Comments = High energy cosmic rays are also expected.
}}

== Model Description ==

To be filled in with updated draft

== Observational Constraints ==

To be filled in with updated draft

Tiny EM Explosions

2018-10-11T10:02:12Z

Jake Gordin:

White Holes

2018-10-11T10:01:09Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = White Holes
|Type = Single
|EnergyMechanism = --
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = Yes
|XrayCounterpart = --
|GammarayCounterpart = Yes
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2014PhRvD..90l7503B, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1611.01243
|Comments = None
}}

== Model Description ==

Should a collapsing star reach the Planck density, becoming a Planck star, it will cease to collapse further and will explode outwards (or bounce) to form a white hole (WH). Due to their age, PBHs or Planck stars are the strongest candidates to form WHs which may be observable today, and the energy they release is consistent with FRBs. A single FRB is expected, accompanied by an IR signal - with a wave length on the order of the exploding star -, as well as Gamma-rays, characterized by the material expelled in the explosion .

== Observational Constraints ==

To be filled in with updated draft

Wandering Pulsar

2018-10-11T10:00:51Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = Wandering Pulsar Beams
|Type = Repeat
|EnergyMechanism = --
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1611.01243
|Comments = Any counterparts will be associated with the pulsar, but are not specified.
}}

== Model Description ==

This model assumes the presence of a steady beam of pulsar emission whose directly randomly changes. If this beam sweeps across the line of sight of an observer, it may be observable as an FRB. The duration of the FRB depends on the speed at which the beam moves across the sky, and hence a wandering beam mitigates the enormous power and high spin-down requirements of giant pulse and flare models.

== Observational Constraints ==

This scenario can also consistently explain two pairs of possibly distinct radio bursts detected in FRB 121102. Details about an emission mechanism or possible counterparts are not given.

SS Crust

2018-10-11T09:59:01Z

Jake Gordin:

Stellar Coronae

2018-10-11T09:58:30Z

Jake Gordin:

Pulsar-BH Interaction

2018-10-11T09:55:24Z

Jake Gordin:

{{FRBTableTemplate
|Category = Interaction
|Progenitor = Pulsar-BH
|Type = Single
|EnergyMechanism = --
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = ?
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1711.09083
|Comments =
}}

== Model Description ==

An enhanced giant pulse generated by a rapidly spun-up neutron star near a spinning black hole could produce a single FRB. A gyroscope is used to model the pulsar's spin-precession, which has been shown to increase rapidly near the event horizon of a Kerr BH. Eventually the spin precession exceeds the pulsar's spin, and the latter can be neglected. As such, the pulsar magnetosphere is essentially rotating around the spin-precession axis. The rapid spin-up causes a giant pulse, whose emission is consistent with an FRB.

== Observational Constraints ==

If two or more bursts are released during the rapid spin-up, the event duration is expected to be >1 ms for an unresolved burst and a double peaked profile is expected if the burst is partially resolved.

NS-WD Merger

2018-10-11T09:53:10Z

Jake Gordin:

{{FRBTableTemplate
|Category = Merger
|Progenitor = NS-WD
|Type = Single
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1712.03509
|Comments =
}}

== Model Description ==
Upon NS-WD coalescence, magnetic reconnection injects relativistic electrons from the surface of the WD into the magnetosphere of the NS to create an FRB. The timescale of the burst is assumed to be from the time of electron injection to the formation of the final merged object. It is predicted that the shorter the intrinsic width of the FRB, the higher the flux density.

== Observational Constraints ==

Of the 28 FRBs analysed (those available at the time), the pulse widths were broader than expected in the NS-WD scenario, but perhaps pulse widths vary more widely between FRBs due to multipath scattering through the IGM.

NS-BH Merger

2018-10-11T09:50:59Z

Jake Gordin:

{{FRBTableTemplate
|Category = Merger
|Progenitor = NS-BH
|Type = Single
|EnergyMechanism = BH battery
|EmissionMechanism = --
|LFRadioCounterpart = --
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = Yes
|GammarayCounterpart = Yes
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1511.02870
|Comments = None
}}

== Model Description ==

During the inspiral of a NS-BH merger, the magnetic field lines of the NS may thread around the BH event horizon in a way similar to a battery powering a circuit, and produce a single FRB.

== Observational Constraints ==
The FRB emission would have a precursor burst and a double peak.

NS to Quark Star

2018-10-11T09:50:35Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collapse
|Progenitor = NS to Quark Star
|Type = Single
|EnergyMechanism = β-decay
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = Yes
|GammarayCounterpart = Yes
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1505.08147
|Comments = The burst is predicted to be several seconds, explainable if the de-dispersion process that stacks frequency channels to a common initial time is incorrect.
}}

== Model Description ==

As a NS spins down, the reduction in centrifugal forces cause the density in the core to increase to the point where neutrons may split in to their constituent parts--a process known as quark deconfinement. This phase transition from neutrons to a quark-gluon plasma triggers a massive explosion--a quark nova--in which the parent NS collapses into a quark star. The outer layers of the NS are ejected at relativistic speeds, generating highly unstable rapid neutron-capture (r-process) elements, which undergo a rapid series of β-decays. The electrons emitted from this decay stream into the magnetosphere to generate synchrotron emission akin to an FRB.

== Observational Constraints ==

Gravitational waves are expected from the explosion and from the quark star oscillation modes.

NS to BH (DM-Induced)

2018-10-11T09:47:51Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collapse
|Progenitor = NS to BH
|Type = Single
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1412.6119
|Comments = None
}}

== Model Description ==

It is possible that a NS could capture ambient DM particles as they scatter off the NS nucleons and become gravitationally bound. Once the DM particles thermalize to the NS temperature, they sink to the center of the NS. Here they accumulate until they reach a critical mass and collapse into a BH. The BH will then engulf the NS, ejecting the NS magnetosphere, causing violent magnetic reconnection. The resultant coherent curvature radiation may be consistent with a single FRB.

== Observational Constraints ==

The lifetime of a NS undergoing DM-induced collapse is proportional to the density of DM in its local environment. In regions of low DM density, NS lifetimes are of the Hubble scale, however where the DM densities are high, the final NS collapse may be observable today. Origins are thus expected to be central regions of high density galaxies, i.e. massive spirals, early type galaxies, and central cluster galaxies.

NS to KNBH

2018-10-11T09:44:16Z

Jake Gordin:

NS Combing

2018-10-11T09:42:59Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = NS Combing
|Type = Both
|EnergyMechanism = Various
|EmissionMechanism = Mag. reconnection
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2017ApJ...836L..32Z, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1801.05436
|Comments = The model can apply to a variety of events, and thus counterparts will depend on the scenario.
}}

== Model Description ==

To be filled in with updated draft

== Observational Constraints ==

To be filled in with updated draft

NS and Primordial BH

2018-10-11T09:41:30Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collision / Interaction
|Progenitor = NS and Primordial BH
|Type = Both
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1704.05931
|Comments = None
}}

== Model Description ==

As a PBH passes through a NS, the gravitational drag from the dense NS matter causes the PBH to slow down. The PBH will pass through the middle of the NS and, after losing sufficient kinetic energy, will be pulled back. The PBH will oscillate a few times before settling at the center of the NS. Here, the PBH will begin to accrete the NS until it is swallowed, causing the NS magnetosphere to be shed. The resulting magnetic reconnection releases an FRB. A repeating FRB may also be accounted for in this scenario: a small PBH will take longer to accrete the NS; as the NS is gradually consumed, multiple bundles of magnetic field lines within the NS may be reconfigured, causing multiple bursts.

== Observational Constraints ==

Gravitational waves are expected counterparts, but may not be detectable at cosmological distances. The model can account multiple peaks, polarized emission and Faraday rotation.

KNBH-BH (Magneto. Collapse)

2018-10-11T09:38:48Z

Jake Gordin:

{{FRBTableTemplate
|Category = Merger
|Progenitor = KNBH-BH
|Type = Single
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Afterglow
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = Afterglow
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1602.06907
|Comments = Can only account for a sub-population of FRBs.
}}

== Model Description ==

For merging BH binaries in which at least one of the BHs is Kerr-Newman, instabilities due to tidal forces induce reconnection in the KNBH prior to coalescence. The magnetic field violently reconnects, triggering strong relativistic shock waves through the surrounding plasma to produce curvature radiation consistent with an FRB.

== Observational Constraints ==

KNBHs have no thermal emission because they lack solid surfaces, and are non-pulsating because their magnetic and rotation axes are aligned.

KNBH-BH (Inspiral)

2018-10-11T09:37:24Z

Jake Gordin:

{{FRBTableTemplate
|Category = Merger
|Progenitor = KNBH-BH
|Type = Single
|EnergyMechanism = Mag. flux change
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Afterglow
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = Yes
|GammarayCounterpart = sGRB <br/> if jet aligned
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1602.04542
|Comments = Unlikely to account for full FRB population.
}}

== Model Description ==

A binary BH system in which at least one of the spinning BHs carries a charge would induce a global magnetic dipole normal to the orbital plane. During inspiral, as the orbital separation decreases, the magnetic flux of the system changes rapidly, which leads to particle bunching and the emission of coherent curvature radiation.

== Observational Constraints ==

For some minimal values of the charge of the BH, this scenario could produce an FRB and a sGRB. The detection of both signals could provide a lower limit on the charge, and the non-detection of a sGRB could provide an upper limit.

Jet-Caviton

2018-10-11T09:36:02Z

Jake Gordin:

{{FRBTableTemplate
|Category = AGN
|Progenitor = Jet-Caviton Interaction
|Type = Both
|EnergyMechanism = Electron scattering
|EmissionMechanism = Bremsst.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Yes
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = Possible GRB
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/abs/2016PhRvD..93b3001R, http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1704.08097
|Comments = None
}}

== Model Description ==

Let us first discuss the formation of AGN jets. Consider a hot accretion disk formed as matter is captured and spirals into a moderately sized BH. Some of the in-falling gas and dust is confined to the poles and ejected in two relativistic jets [229]. Hot gas clouds of varying densities surround the BH, forming a toroid that extends a few parsecs from the BH. As the AGN jet interacts with the clouds, it becomes narrowly collimated. The relativistic e+/e− beam encounters material at the center of the host galaxy, and strong turbulence is produced by plasma instabilities. The total pressure and the ponderomotive force (experienced by a charged particle in an oscillating electric field) cause electrons and ions to separate. These regions, called cavitons, are filled by a strong electrostatic field. Electrons from the beam that pass through the caviton are coherently scattered and emit strongly beamed Bremsstrahlung radiation in pulses. FRBs may be single or repeating.

== Observational Constraints ==

Radiation might be linearly polarized if there is a local magnetic field, however the 100% polarization degree of FRB 121102 would be difficult to account for in this scenario. The persistent scintillating radio emission from the AGN is an expected counterpart, which agrees with observations of FRB 121102.

Axion Star and NS

2018-10-11T09:32:32Z

Jake Gordin:

Axion Star and BH

2018-10-11T09:30:10Z

Jake Gordin:

Axion Quark Nugget and NS

2018-10-11T09:28:46Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collision / Interaction
|Progenitor = Axion Quark Nuggest and NS
|Type = Repeat
|EnergyMechanism = Mag. reconnection
|EmissionMechanism = Curv.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = Possible
|MicrowaveCounterpart = Possible
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1806.02352
|Comments = None
}}

== Model Description ==

In close analogy with the axion quark nugget (AQN) mechanism for generating solar nano flares, an AQN falling through an opportunely complicated region in a NS’s magnetosphere may be able to produce sufficient magnetic energy to power FRBs. Shock waves caused by the infalling AQN would trigger magnetic reconnection, and produce a giant flare.

== Observational Constraints ==

The predicted event rate is consistent with observations, but the emission timescale (∼ 10 − 100 ms) is larger than what is observed. This discrepancy can be accounted for if the beam moves across the sky, allowing us only a glimpse of the emission. A curvature radiation mechanism is invoked, which predicts a maximum cut-off frequency at infra-red wavelengths; observed counterparts with higher frequencies would invalidate this model. Given the random nature of these events, repeating FRBs would be non-periodic. A correlation between the total energy and duration of the flare is predicted, however because only a fraction of the entire beam would be observed, this relationship would be difficult to verify.

Axion Cloud and BH

2018-10-11T09:26:18Z

Jake Gordin:

{{FRBTableTemplate
|Category = Collision / Interaction
|Progenitor = Superradiant Axion Cloud and BH
|Type = Repeat
|EnergyMechanism = Laser
|EmissionMechanism = Synch.
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = Yes
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1709.06581
|Comments = Observational counterparts could be associated with electron-positron annihilation and/or positronium.
}}

== Model Description ==

Spinning BHs have superradiant instabilities, and thus may be surrounded by a dense superradiant axion cloud. Similarly to how a laser can be generated by stimulated axion decay in dense axion clusters, a laser can be triggered in superradiant axion clusters. Such is known as a black hole laser powered by axion superradiant instabilities (BLAST). For a BLAST’s emission to be consistent with FRB observations, the required mass dictates that the BHs be primordial. However, because PBHs form when over densities of gas collapse, they do not have spin, and are unlikely to spin up via accretion. The merging of two PBHs is thus considered for FRBs, where the required spin and resultant superradiant instabilities can be induced. Repeating bursts could occur: the BLAST will form a photon plasma that blocks axion decay and thus halts lasing until e+/e− annihilation reduces the plasma density, and the process can restart.

== Observational Constraints ==

Observational counterparts could be associated with e+e− annihilation and/or positronium (a bound particle of an e+ and e−), though these are not specified. GWs are also expected.

Annihilating Mini BHs

2018-10-11T09:20:16Z

Jake Gordin:

Alien Light Sails

2018-10-11T08:59:13Z

Jake Gordin:

{{FRBTableTemplate
|Category = Other
|Progenitor = Alien Light Sails
|Type = Repeat
|EnergyMechanism = Artificial transmitter
|EmissionMechanism = --
|LFRadioCounterpart = Yes
|HFRadioCounterpart = --
|MicrowaveCounterpart = --
|THzCounterpart = --
|OIRCounterpart = --
|XrayCounterpart = --
|GammarayCounterpart = --
|GWCounterpart = --
|NeutrinoCounterpart = --
|References = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1701.01109
|Comments = Highly speculative.
}}

== Model Description ==

Extragalactic, artificial beam-powered light sails have been proposed as an FRB theory, however such a concept is highly speculative.

== Observational Constraints ==

---

AGN-SS

2018-10-11T08:53:56Z

Jake Gordin: