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Open accessJournal ArticleDOI: 10.3390/UNIVERSE7030056

Emission Mechanisms of Fast Radio Bursts

04 Mar 2021-Universe (Multidisciplinary Digital Publishing Institute)-Vol. 7, Iss: 3, pp 56
Abstract: Fast radio bursts (FRBs) are recently discovered mysterious single pulses of radio emission, mostly coming from cosmological distances (∼1 Gpc). Their short duration, ∼1 ms, and large luminosity demonstrate coherent emission. I review the basic physics of coherent emission mechanisms proposed for FRBs. In particular, I discuss the curvature emission of bunches, the synchrotron maser, and the emission of radio waves by variable currents during magnetic reconnection. Special attention is paid to magnetar flares as the most promising sources of FRBs. Non-linear effects are outlined that could place bounds on the power of the outgoing radiation.

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Topics: Radio wave (56%), Magnetar (52%), Maser (52%)

14 results found

Open access
J. G. Kirk1, O. Skjaeraasen1Institutions (1)
01 Jan 2004-
Abstract: The conversion of the Crab pulsar wind from one dominated by Poynting flux close to the star to one dominated by particle-born energy at the termination shock is considered. The idea put forward by Coroniti (1990) and criticised by Lyubarsky & Kirk (2001) that reconnection in a striped wind is responsible, is generalised to include faster prescriptions for the a priori unknown dissipation rate. Strong acceleration of the wind is confirmed, and the higher dissipation rates imply complete conversion of Poynting flux into particle-born flux within the unshocked wind.

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Topics: Crab Pulsar (59%), Poynting vector (54%), Flux (51%) ... read more

11 Citations

Open accessJournal ArticleDOI: 10.3847/1538-4357/AC14B5
Yuan-Pei Yang1, Bing Zhang2Institutions (2)
Abstract: The recent discovery of a Galactic fast radio burst (FRB) occurring simultaneously with an X-ray burst (XRB) from the Galactic magnetar SGR J1935+2154 implies that at least some FRBs arise from magnetar activities. We propose that FRBs are triggered by crust fracturing of magnetars, with the burst event rate depending on the magnetic field strength in the crust. Since the crust fracturing rate is relatively higher in polar regions, FRBs are preferred to be triggered near the directions of multipolar magnetic poles. Crust fracturing produces Alfven waves, forming a charge starved region in the magnetosphere and leading to non-stationary pair plasma discharges. An FRB is produced by coherent plasma radiation due to nonuniform pair production across magnetic field lines. Meanwhile, the FRB-associated XRB is produced by the rapid relaxation of the external magnetic field lines. In this picture, the sharp-peak hard X-ray component in association with FRB 200428 is from a region between adjacent trapped fireballs, and its spectrum with a high cutoff energy is attributed to resonant Compton scattering. The persistent X-ray emission is from a hot spot heated by the magnetospheric activities, and its temperature evolution is dominated by magnetar surface cooling. Within this picture, magnetars with stronger fields tend to produce brighter and more frequent repeated bursts.

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Topics: Magnetar (59%), Fast radio burst (54%), Magnetosphere (51%)

10 Citations

Open accessJournal ArticleDOI: 10.3390/UNIVERSE7030076
23 Mar 2021-Universe
Abstract: The origin and phenomenology of the Fast Radio Burst (FRB) remains unknown despite more than a decade of efforts. Though several models have been proposed to explain the observed data, none is able to explain alone the variety of events so far recorded. The leading models consider magnetars as potential FRB sources. The recent detection of FRBs from the galactic magnetar SGR J1935+2154 seems to support them. Still, emission duration and energetic budget challenge all these models. Like for other classes of objects initially detected in a single band, it appeared clear that any solution to the FRB enigma could only come from a coordinated observational and theoretical effort in an as wide as possible energy band. In particular, the detection and localisation of optical/NIR or/and high-energy counterparts seemed an unavoidable starting point that could shed light on the FRB physics. Multiwavelength (MWL) search campaigns were conducted for several FRBs, in particular for repeaters. Here we summarize the observational and theoretical results and the perspectives in view of the several new sources accurately localised that will likely be identified by various radio facilities worldwide. We conclude that more dedicated MWL campaigns sensitive to the millisecond–minute timescale transients are needed to address the various aspects involved in the identification of FRB counterparts. Dedicated instrumentation could be one of the key points in this respect. In the optical/NIR band, fast photometry looks to be the only viable strategy. Additionally, small/medium size radiotelescopes co-pointing higher energies telescopes look a very interesting and cheap complementary observational strategy.

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6 Citations

Open accessJournal ArticleDOI: 10.3390/UNIVERSE7040085
01 Apr 2021-Universe
Abstract: Fast Radio Bursts (FRBs) represent a novel tool for probing the properties of the universe at cosmological distances. The dispersion measures of FRBs, combined with the redshifts of their host galaxies, has very recently yielded a direct measurement of the baryon content of the universe, and has the potential to directly constrain the location of the “missing baryons”. The first results are consistent with the expectations of ΛCDM for the cosmic density of baryons, and have provided the first constraints on the properties of the very diffuse intergalactic medium (IGM) and circumgalactic medium (CGM) around galaxies. FRBs are the only known extragalactic sources that are compact enough to exhibit diffractive scintillation in addition to showing exponential tails which are typical of scattering in turbulent media. This will allow us to probe the turbulent properties of the circumburst medium, the host galaxy ISM/halo, and intervening halos along the path, as well as the IGM. Measurement of the Hubble constant and the dark energy parameter w can be made with FRBs, but require very large samples of localised FRBs (>103) to be effective on their own—they are best combined with other independent surveys to improve the constraints. Ionisation events, such as for He ii, leave a signature in the dispersion measure—redshift relation, and if FRBs exist prior to these times, they can be used to probe the reionisation era, although more than 103 localised FRBs are required.

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Topics: Hubble's law (53%), Galaxy (52%), Dark energy (51%) ... read more

4 Citations

Open accessJournal ArticleDOI: 10.1103/PHYSREVLETT.127.035101
Abstract: Relativistic magnetized shocks are a natural source of coherent emission, offering a plausible radiative mechanism for Fast Radio Bursts (FRBs). We present first-principles 3D simulations that provide essential information for the FRB models based on shocks: the emission efficiency, spectrum, and polarization. The simulated shock propagates in an $e^\pm$ plasma with magnetization $\sigma>1$. The measured fraction of shock energy converted to coherent radiation is $\simeq 10^{-3} \, \sigma^{-1}$, and the energy-carrying wavenumber of the wave spectrum is $\simeq 4 \,\omega_{\rm c}/c$, where $\omega_{\rm c}$ is the upstream gyrofrequency. The ratio of the O-mode and X-mode energy fluxes emitted by the shock is $\simeq 0.4\,\sigma^{-1}$. The dominance of the X-mode at $\sigma\gg 1$ is particularly strong, approaching 100% in the spectral band around $2\,\omega_{\rm c}$. We also provide a detailed description of the emission mechanism for both X- and O-modes.

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4 Citations


142 results found

Journal ArticleDOI: 10.1086/186413
Abstract: It is proposed that the main observational signature of magnetars, high-field neutron stars, is gamma-ray bursts powered by their vast reservoirs of magnetic energy. If they acquire large recoils, most magnetars are unbound from the Galaxy or reside in an extended, weakly bound Galactic corona. There is evidence that the soft gamma repeaters are young magnetars. It is argued that a convective dynamo can also generate a very strong dipole field after the merger of a neutron star binary, but only if the merged star survives for as long as about 10-100 ms. Several mechanisms which could impart a large recoil to these stars at birth, sufficient to escape from the Galactic disk, are discussed.

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Topics: Neutron star (65%), Anomalous X-ray pulsar (65%), Magnetar (58%) ... read more

2,304 Citations

Open accessJournal ArticleDOI: 10.1126/SCIENCE.1147532
02 Nov 2007-Science
Abstract: Pulsar surveys offer a rare opportunity to monitor the radio sky for impulsive burst-like events with millisecond durations. We analyzed archival survey data and found a 30-jansky dispersed burst, less than 5 milliseconds in duration, located 3 degrees from the Small Magellanic Cloud. The burst properties argue against a physical association with our Galaxy or the Small Magellanic Cloud. Current models for the free electron content in the universe imply that the burst is less than 1 gigaparsec distant. No further bursts were seen in 90 hours of additional observations, which implies that it was a singular event such as a supernova or coalescence of relativistic objects. Hundreds of similar events could occur every day and, if detected, could serve as cosmological probes.

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Topics: Fast radio burst (62%), Small Magellanic Cloud (54%), Pulsar (54%) ... read more

1,431 Citations

Open accessBook
01 Jan 1964-
Abstract: Green's function techniques are used to treat the propagation of electromagnetic waves in uniform, weakly interacting plasmas near equilibrium in the absence of external magnetic fields. The frequency and the damping of electromagnetic waves in a medium are related to the local complex conductivity tensor, which is calculated by the diagrammatic techniques of modern field theory. Physical quantities are calculated in terms of a consistent many-particle perturbation expansion in powers of a (weak) coupling parameter. An open-diagram technique is introduced which simplifies the calculation of absorptive parts. For longwavelength longitudinal waves (i.e., electron plasma oscillations) it is found that the main absorption mechanism in the electron-ion plasma is the two-particle collision process appropriately corrected for collective effects and not the one-particle (or Landau) damping process. Electron-ion collisions produce a damping effect which remains finite for long wavelengths. The effect of electron-electron collisions vanishes in this limit. The absorption of transverse radiation is also considered; calculations for the electron-ion plasma are in essential agreement with the recent work of Dawson and Oberman. The results for the absorptive part of the conductivity tensor for long-wavelength electromagnetic waves in a plasma where the phase velocity au/k is much greater than the rms particle velocity is for the electron-ion plasma: O„O,~kgb C, ( )

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Topics: Wave propagation (80%), Surface wave (78%), Plane wave (72%) ... read more

1,404 Citations

Open access
01 Jan 1970-

1,110 Citations

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