ABSTRACT There are several phenomenological similarities between soft gamma repeaters (SGRs) and fast radio bursts (FRBs), including duty factors, timescales, and repetition. The sudden release of ...magnetic energy in a neutron star magnetosphere, as in popular models of SGRs, can meet the energy requirements of FRBs, but requires both the presence of magnetospheric plasma, in order for dissipation to occur in a transparent region, and a mechanism for releasing much of that energy quickly. FRB sources and SGRs are distinguished by long-lived (up to thousands of years) current-carrying coronal arches remaining from the formation of the young neutron star, and their decay ends the phase of SGR/AXP/FRB activity even though "magnetar" fields may persist. Runaway increases in resistance when the current density exceeds a threshold, releases magnetostatic energy in a sudden burst, and produces high brightness GHz emission of FRB by a coherent process. SGRs are produced when released energy thermalizes as an equlibrium pair plasma. The failures of some alternative FRB models and the non-detection of SGR 1806-20 at radio frequencies are discussed in the appendices.
ABSTRACT
Popular models of repeating fast radio bursts (FRBs; and perhaps of all FRBs) involve neutron stars because of their high rotational or magnetostatic energy densities. These models take one ...of two forms: giant but rare pulsar-like pulses like those of rotating radio transients, and outbursts like those of soft gamma repeaters. Here I collate the evidence, recently strengthened, against these models, including the absence of Galactic micro-FRBs, and attribute the 16 d periodicity of FRB 180916.J0158+65 to the precession of a jet produced by a massive black hole’s accretion disc.
ABSTRACT The widths, dispersion measures (DMs), dispersion indices, and fluences of Fast Radio Bursts (FRBs) impose coupled constraints that all models must satisfy. The non-monotonic dependence of ...burst widths (after deconvolution of instrumental effects) on DMs excludes the intergalactic medium as the location of scattering that broadens the FRBs in time. Temporal broadening far greater than that of pulsars at similar high Galactic latitudes implies that scattering occurs close to the sources where high densities and strong turbulence or heterogeneity are plausible. FRB energetics are consistent with supergiant pulses from young, fast, high-field pulsars at cosmological distances. The distribution of FRB DMs is: (1) inconsistent with that of expanding clouds (such as SNRs); (2) inconsistent with space-limited source populations (such as the local Supercluster); and (3) consistent with intergalactic dispersion of a homogeneous source population at cosmological distances. Finally, the FRB - relation also indicates a cosmological distribution aside from the anomalously bright Lorimer burst.
ABSTRACT
Variations of the dispersion measures (DM) and rotation measures (RM) of fast radio bursts (FRBs) 121102 indicate magnetic fields ∼3–17 mG in the dispersing plasma. The electron density may ...be ${\sim}10^4\,$ cm−3. The observed time scales ∼1 yr constrain the size of the plasma cloud. Increasing DM excludes simple models involving an expanding supernova remnant, and the non-zero RM excludes spherical symmetry. The varying DM and RM may be attributable to the motion of plasma into or out of the line of sight to or changing electron density within slower moving plasma. The extraordinarily large RM of FRB 121102 implies an environment, and possibly also a formation process and source, qualitatively different from those of other FRB. The comparable and comparably varying RM of SGR/PSR J1745−2900 suggests it as a FRB candidate. Appendix A discusses the age of FRB 121102 in the context of a ‘Copernican Principle’.
Precession and Jitter in FRB 180916B Katz, J I
Monthly notices of the Royal Astronomical Society. Letters,
10/2022, Letnik:
516, Številka:
1
Journal Article
Recenzirano
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ABSTRACT
Recent CHIME/FRB observations of the periodic repeating fast radio bursts (FRB) 180916B have produced a homogeneous sample of 44 bursts. These permit a redetermination of the modulation ...period and phase window, in agreement with earlier results. If the periodicity results from the precession of an accretion disc, in analogy with those of Her X-1, SS 433, and many other superorbital periods, the width of the observable phase window indicates that the disc axis jitters by an angle of about 0.14 of the inclination angle, similar to the ratio of 0.14 in the well-observed jittering jet source SS 433.
The FRB–SGR connection Katz, J I
Monthly notices of the Royal Astronomical Society,
12/2020, Letnik:
499, Številka:
2
Journal Article
Recenzirano
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ABSTRACT
The discovery that the Galactic Soft Gamma Repeater (SGR) 1935+2154 emitted Fast Radio Burst (FRB) 200428 simultaneous with a gamma-ray flare, demonstrated the common source and association ...of these phenomena. If FRB radio emission is the result of coherent curvature radiation, the net charge of the radiating ‘bunches’ or waves may be inferred from the radiated fields, independent of the mechanism by which the bunches are produced. A statistical argument indicates that the radiating bunches must have a Lorentz factor ⪆ 10. The observed radiation frequencies indicate that their phase velocity (pattern speed) corresponds to Lorentz factors ⪆ 100. Coulomb repulsion implies that the electrons making up these bunches have yet larger Lorentz factors, limited by their incoherent curvature radiation. These electrons also Compton scatter the soft gamma-rays of the SGR. In FRB 200428, the power they radiated coherently at radio frequencies exceeded that of Compton scattering, but in more luminous SGR outbursts, Compton scattering dominates, precluding the acceleration of energetic electrons. This explains the absence of a FRB associated with the giant 2004 December 27 outburst of SGR 1806−20. SGR with luminosity ≳ 1042 erg s–1 are predicted not to emit FRB, while those of lesser luminosity can do so. ‘Superbursts’ like FRB 200428 are produced when narrowly collimated FRB are aligned with the line of sight; they are unusual, but not rare, and ‘cosmological’ FRB may be superbursts.
ABSTRACT
Popular fast radio burst (FRB) models involve rotating magnetized neutron stars, yet no rotational periodicities have been found. Small data sets exclude exact periodicity in FRB 121102. ...Recent observations of over 1500 bursts from each of FRB 121102 and FRB 20201124A have also not found periodicity. Periodograms of events with cosine-distributed random offsets as large as ±0.6P from a strict period P would still reveal the underlying periodicity. The sensitivity of periodograms of long data series, such as bursts observed on multiple days, to slow frequency drifts is mitigated by considering individual observing sessions, and results are shown for FRB 121102. Models of repeating FRB without intrinsic periodicity are considered, as are models of apparently non-repeating FRBs.
ABSTRACT
The activity of at least one repeating fast radio burst (FRB) source is periodically modulated. If this modulation is the result of precession of the rotation axis and throat of an accretion ...disc around a black hole, driven by a companion that is also the source of accreted mass, then it may be possible to constrain the mass of the black hole. The dynamics is analogous to that of superorbital periods in ordinary mass-transfer binaries in which the accreting object may be a stellar-mass black hole, a neutron star or a white dwarf, but in the FRB source it may be an intermediate-mass black hole. In a semidetached (mass-transferring) binary, the orbital period is nearly proportional to the −1/2 power of the mean density of the mass-losing star and nearly independent of the mass of the primary, but the ratio of precessional to orbital periods scales approximately as the −2/3 power of the mass ratio for small mass ratios (massive accretors). Assuming a value for the secondary’s density and identifying the observed modulation period as a disc precession period would determine the mass ratio and the mass of the black hole. This model and magnetar-SNR (supernova remnant) models make distinguishable predictions of the evolution of the rotation measure that may soon be tested in FRB 121102.
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