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On the Origin of Fast Radio Bursts (FRBs)

“…The inferred energy and mass associated with the source are somewhat low compared to those of typical supernova ejecta (A similar conclusion has been reached in recent analyses of FRB 121102 (Murase et al 2016;Piro 2016;Kashiyama & Murase 2017;Beloborodov 2017;Dai et al 2017;Katz 2017a), suggesting that the source is a magnetarwind nebula confined by a (very) low mass supernova ejecta). This may suggest some type of a "weak stellar explosion", where a neutron star is formed with relatively low mass and energy ejection (and hence possibly not associated with a typical supernova remnant).…”

“…Our approach differs from that of earlier analyses, which attempt to interpret the emission in terms of an assumed model of the source (e.g. Kashiyama & Murase 2017;Metzger et al 2017;Beloborodov 2017;Dai et al 2017;Katz 2017a;Piro & Burke-Spolaor 2017;Katz 2017b;Zhang 2017), typically of emission from a "magnetar wind nebula" confined by a supernova ejecta. We derive constraints on the parameters of the plasma producing the persistent emission, which are independent of assumptions implied by adopting a specific 1 Dept.…”

“…This challenge has been realized by Beloborodov (2017), who suggests that the required electron density is produced by the ejection of mass accompanying a giant magnetar flare. Efficient mixing of this mass into the persistent magnetar wind, accompanied by efficient heating of the electrons to near equipartition, may produce the required plasma parameters.…”

“…In this model, the flare drives a collisionless shock into the pair-plasma, and coherent synchrotron emission is produced at the gyration frequency of the electrons due to an anisotropic particle distribution at the shock front (it is worth noting in this context that synchrotron maser radio emission due to anisotropic relativistic electron distribution has been suggested to operate in astrophysical plasmas by Sazonov (1973), and reintroduced more recently in the context of FRBs by Ghisellini (2017)). A significant challenge faced by this model is related to the fact that the flare energy, ∼ 10 48 erg, is ∼ 10 9 times larger than the FRB energy (Lyubarsky (2014); Metzger et al (2017); A variant of this model, where the ratio between the flare energy and the FRB energy is smaller, ∼ 10 5 , has been proposed by Beloborodov (2017)). It is thus challenging to explain within this model the FRB energy without a complete detailed understanding of the physics, including the physics of collisionless shocks, which is not yet in hand.…”

“…Our analysis goes beyond that of Beloborodov (2017), who derived the electron number density and the total energy, E, assuming specific values for the source size, R = 10 17 cm, age, t persist = 30 yr, and magnetic field to electron energy density, ǫ B /ǫ e ≈ 1. We show that the values of R, t persist and ǫ B /ǫ e are constrained by the observed dispersion measure and by the lack of its variation, and derive the allowed range of parameters of both the radiating and the confining plasmas(under the assumption that the FRB source resides within the persistent source, the dispersion measure of the FRBs constrains the properties of the plasma producing the persistent emission).…”