On the Origin of Fast Radio Bursts (FRBs)

We derive stringent constraints on the persistent source associated with FRB 121102: size 0.3 < R-17.5 = (R/10(17.5) cm) < 3, age < 10(2.5) year, energy E approximate to 10(49) (epsilon(e)/0.2 GeV)(3) erg, characteristic electron energy 0.1 <= epsilon(e)/1 GeV <= 0.5; the radiating plasma is confined by a cold plasma of mass M-c < 10(-1.5)R(17.5)(4) M-circle dot; these properties are inconsistent with typical magnetar wind nebulae model predictions. The fact that epsilon(e) similar to m(p)c(2) suggests that the hot plasma was created by the ejection of a mildly relativistic, M approximate to E/c(2) approximate to 10(-5) M-circle dot shell, which propagated into an extended ambient medium or collided with a pre-ejected shell. Independent of the persistent source model, we suggest a physical mechanism for the generation of fast radio bursts (FRBs): the ejection from an underlying compact object, R-s = 10(6)R(s,6) cm, of highly relativistic shells with energy E-s = 10(41) E-41 erg and Lorentz factor gamma(s) = 10(3)E(41)(1/8) R-s,6(-3/8), into a surrounding e - p plasma with density n similar to 10(-1) cm(-3) (consistent with that inferred for the persistent source). For E-s similar to observed FRB energies, plasma conditions appropriate for strong synchrotron maser emission at v(coh) approximate to 0.5E(41)(1/4) R-s,6(-3/4) GHz are formed. A significant fraction of the deposited energy is converted to an FRB with duration R-s/c, accompanied by similar to 10 MeV gamma-rays carrying less energy than the FRB. The inferred energy and mass associated with the source suggest some type of a weak stellar explosion, where a neutron star is formed with relatively low mass and energy ejection. However, the current upper limit on R does not allow one to rule out M-c similar to 1M(circle dot), or the ejection of a larger mass well before the ejection of the confining shell.