Macquart, J.-P. and Shannon, R. M. and Bannister, K. W. and James, C. W. and Ekers, R. D. and Bunton, J. D. (2019) The Spectral Properties of the Bright Fast Radio Burst Population. The Astrophysical Journal, 872 (2). L19. ISSN 2041-8213
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Abstract
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 $\alpha =-{1.5}_{-0.3}^{+0.2}$ (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^\circ \pm 5^\circ $. 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.
Item Type: | Article |
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Subjects: | Euro Archives > Physics and Astronomy |
Depositing User: | Managing Editor |
Date Deposited: | 08 Jun 2023 06:29 |
Last Modified: | 22 Nov 2023 04:55 |
URI: | http://publish7promo.com/id/eprint/2665 |