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17th of July 2020
Fast Radio Burst profiles
by Qiu et al.
The pulse morphology of fast radio bursts (FRBs) provides key information in both understanding progenitor physics and the plasma medium through which the burst propagates. Qiu et al. present a study of the profiles of 33 bright FRBs detected by ASKAP. They identify seven FRBs with measureable intrinsic pulse widths, including two FRBs that have been seen to repeat. They also identify five FRBs with evidence of millisecond timescale pulse broadening caused by scattering in inhomogeneous plasma. We find no evidence for a relationship between pulse broadening and extragalactic dispersion measure. The scattering could be either caused by extreme turbulence in the host galaxy or chance propagation through foreground galaxies.

The figure above shows two subband pulse profiles of FRB 180110, detected with a high signal-to-noise ratio and with a significant scattering tail. The best-fitting model and the residual for each subband are plotted. The exponential broadening scales with frequency using an exponential power law with an index of −3.8 for this burst. This frequency dependence is consistent with the spectral index measured from pulsars scattered by the interstellar medium in our Galaxy. However, FRB 180110 was detected at a high Galactic latitude (~50 degrees) and the Galactic contribution cannot produce scattering of the observed magnitude. This suggests that the scattering is likely to be caused by propagation through plasma outside the Milky Way, either in the host galaxy or in an intervening galaxy or galaxy halo. The paper will be published in Monthly Notices of the Royal Astronomical Society.

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