Emission Mechanisms of Fast Radio Bursts

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.

The fast radio burst FRB 20201124A in a star-forming region: Constraints to the progenitor and multiwavelength counterparts

“…Hundreds of these events have now been discovered (CHIME/FRB Collaboration 2021a), and yet their progenitor systems remain unknown. A leading candidate source is a highly magnetized neutron star (NS), known as a magnetar (Popov & Postnov 2010;Katz 2016;Metzger et al 2017;Beloborodov 2017;Kumar et al 2017;Wadiasingh & Timokhin 2019;Lyubarsky 2021;Yang & Zhang 2021), as supported by the recent detection of FRB-like radio bursts from a soft gamma-ray repeater in our galaxy (Scholz & CHIME/FRB Collaboration 2020;Bochenek et al 2020;Li et al 2021;Mereghetti et al 2020). However, the heterogeneous environment of FRBs and their empirical distinction that spans two classes (repeaters and non-repeaters) leave the door open to multiple progenitor channels (Zhang 2020).…”

Probing the Universe with Fast Radio Bursts

“…The progenitors for FRBs remain a mystery, with a wide range of theories having been advanced to account for their properties, including those involving supernovae in which the FRB is a feature of a young, expanding supernova remnant [27,28] and super-luminous supernovae [29]; the merger/collision of two compact objects such as binary neutron stars (NS-NS) [30][31][32][33], binary white dwarfs (WD-WD) [34] and white dwarf-black hole mergers (WD-BH), the latter via the reconnection of magnetic material [35]; energetic activities from isolated compact objects such as giant pulses from extragalactic pulsars [36]; giant flares from magnetars [37,38]; collision/interaction of neutron stars with AGN [39] and NS "combing" [40]; collapse of supramassive neutron stars [41]; superconducting cosmic strings [42]; possible connection with gamma-ray bursts (GRBs) [43]; and alien beams driving light sails [44]. Platts et al [45], Zhang [46], Xiao et al [47] and Lyubarsky [48] summarise FRB progenitor theories and emission mechanisms.…”

Coherent inverse Compton scattering by bunches in fast radio bursts

“…Some of these mechanisms have been reinvented to interpret FRB coherent emission (e.g. Lu & Kumar 2018;Zhang 2020;Xiao et al 2021;Lyubarsky 2021, for surveys of various mechanisms discussed in the literature).…”

“…Within the FRB context, a widely discussed possibility is coherent curvature radiation by bunches (Katz 2014;Kumar et al 2017;Yang & Zhang 2018;Lu & Kumar 2018;Wang et al 2019;Kumar & Bošnjak 2020;Lu et al 2020;Yang et al 2020;Wang & Lai 2020;Cooper & Wijers 2021). Another related mechanism is the so-called "synchrotron maser" mechanism in 90 o magnetized relativistic shocks, which in fact invoke cyclotron-radiating bunches of charged particles in momentum space (Lyubarsky 2014;Beloborodov 2017Metzger et al 2019;Plotnikov & Sironi 2019;Margalit et al 2020). These mechanisms can interpret some FRB emission properties but also suffer from criticisms in theoretical and/or observational aspects (e.g.…”