paper

The FRB-SGR Connection

arXiv:2006.03468 · doi:10.1093/mnras/staa3042

Abstract

The discovery that the Galactic SGR 19352154 emitted 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 . The observed radiation frequencies indicate that their phase velocity (pattern speed) corresponds to Lorentz factors . Coulomb repulsion implies that the electrons making up these bunches may 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 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 27 December 2004 outburst of SGR 180620. SGR with luminosity ergs/s do not 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.

9 pp., 1 fig. Two new paragraphs at end predicting observable FRB from other SGR

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