http://arxiv.org/abs/2305.08649
The extremely high brightness temperatures of fast radio bursts (FRBs) imply that the radiation process must be coherent, but the radiation mechanism is still unknown. The observed properties of narrow spectra and polarization distributions could be used to constrain the radiation mechanism of FRBs. In this work, we discuss the implications of the spectra and polarizations of FRBs from the perspective of intrinsic radiation mechanisms. We first analyze the observed relative spectral bandwidth of radio bursts from an FRB repeater. Furthermore, we generally discuss the properties of the spectra and polarization of the radiation mechanisms involving the relativistic particle’s perpendicular acceleration, which depends on the relation between the particle’s deflection angle $\psi$ and the radiation beaming angle $1/\gamma$. We find that: (1) If the narrow spectra of FRBs are attributed to the intrinsic radiation mechanism of a single particle, the condition of $\gamma\psi\ll1$ would be necessary, in which scenario, the observed number fraction between linearly and circularly polarized bursts of some FRB repeaters might be due to the propagation effects; (2) Coherent process by multiple particles with some special distributions can lead to a narrow spectrum even for the scenario with $\gamma\psi\gg1$; (3) If the observed number fraction between linearly and circularly polarized bursts is attributed to the radiation mechanism with $\gamma\psi\gg1$, the cumulative distributions of the linear and circular polarization degrees would mainly depend on the particle’s beaming distribution.
Y. Yang
Tue, 16 May 23
71/83
Comments: 14 pages, 12 figures, 1 table. Submitted to MNRAS. Comments welcome!!