Observed Steep and Shallow Spectra, Narrow and Broadband Spectra, Multi-frequency Simultaneous Spectra, and Statistical Fringe Spectra in Fast Radio Bursts: Various Faces of Intrinsic Quasi-periodic Spectra?

In this paper, through analysis, modelings, and simulations, we show that if the spectra of fast radio bursts (FRBs) are intrinsically quasi-periodic spectra, likely produced by coherent curvature radiation from quasi-periodic structured bunches, then the observed steep and shallow spectra, narrow and broadband spectra, multi-frequency simultaneous spectra, as well as possible statistical fringe spectra in FRBs, could all be various manifestations of these intrinsically quasi-periodic spectra. If so, the period properties of the structured bunches, as inferred from the observed multi-frequency simultaneous spectra and potential statistical fringe spectra, may provide valuable insights into the mechanisms behind the formation of such structured bunches.