2019ApJ...872L..19M -
Astrophys. J., 872, L19-L19 (2019/February-3)
The spectral properties of the bright fast radio burst population.
MACQUART J.-P., SHANNON R.M., BANNISTER K.W., JAMES C.W., EKERS R.D. and BUNTON J.D.
Abstract (from CDS):
We examine the spectra of 23 fast radio bursts (FRBs) detected in a fly's-eye survey with the Australian SKA Pathfinder, including those of three bursts not previously reported. The mean spectral index of α=-1.5–0.3+0.2 (Fν ∝ να) is close to that of the Galactic pulsar population. The sample is dominated by bursts exhibiting a large degree of spectral modulation: 17 exhibit fine-scale spectral modulation with an rms exceeding 50% of the mean, with decorrelation bandwidths (half-maximum) ranging from ≃1 to 49 MHz. Most decorrelation bandwidths are an order of magnitude lower than the >=30 MHz expected of Galactic interstellar scintillation at the Galactic latitude of the survey, | b| =50○±5○^. However, these bandwidths are consistent with the ∼ν4 scaling expected of diffractive scintillation when compared against the spectral structure observed in bright UTMOST FRBs detected at 843 MHz. A test of the amplitude distribution of the spectral fluctuations reveals only 12 bursts consistent at better than a 5% confidence level with the prediction of 100%-modulated diffractive scintillation. Five of six FRBs with a signal-to-noise ratio exceeding 20 are only consistent with this prediction at less than 1% confidence. Nonetheless, there is weak evidence (92%-94% confidence) of an anti-correlation between the amplitude of the spectral modulation and dispersion measure (DM), which suggests that it originates as a propagation effect. This effect is corroborated by the smoothness of the higher-DM Parkes FRBs, and could arise due to quenching of diffractive scintillation (e.g., in the interstellar medium of the host galaxy) by angular broadening in the intergalactic medium.
Abstract Copyright:
© 2019. The American Astronomical Society. All rights reserved.
Journal keyword(s):
radiation mechanisms: non-thermal - surveys
Simbad objects:
30
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