Kavli Affiliate: Renxin Xu
| First 5 Authors: Wei-Yang Wang, Yuan-Pei Yang, Hong-Bo Li, Jifeng Liu, Renxin Xu
| Summary:
Fast radio bursts (FRBs) can present a variety of polarization properties,
and some of them have narrow spectra. We study spectral properties from
perspectives of intrinsic radiation mechanisms and absorption during the waves
propagating in the magnetosphere. The intrinsic radiation mechanisms are
considered by invoking quasi-periodic bunch distribution and perturbations on
charged bunches moving on curved trajectories. The narrow-band emission likely
reflects some quasi-periodic structure on the bulk of bunches, which may be due
to quasi-periodically sparking in a “gap” or quasi-monochromatic Langmuir
waves. A sharp spike would appear at the spectrum if the perturbations can
induce a monochromatic oscillation of bunches, however, it is hard to create a
narrow spectrum because the Lorentz factor has large fluctuations so that the
spike disappears. Both the bunching mechanism and perturbations scenarios share
the same polarization properties with a uniformly distributed bulk of bunches.
We investigate absorption effects including Landau damping and curvature
self-absorption in the magnetosphere, which are significant at low frequencies.
Subluminous O-mode photons can not escape from the magnetosphere due to the
Landau damping, leading to a height-dependent lower frequency cut-off. Spectra
can be narrow when the frequency cut-off is close to the characteristic
frequency of curvature radiation, while such conditions can only be met
sometimes. The spectral index is 5/3 at low-frequency bands due to the
curvature self-absorption but not as steep as the observations. The intrinsic
radiation mechanisms are more likely to generate the observed narrow spectra of
FRBs rather than the absorption effects.
| Search Query: ArXiv Query: search_query=au:”Renxin Xu”&id_list=&start=0&max_results=3