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A Toy Model for the Time–Frequency Structure of Fast Radio Bursts: Implications for the CHIME/FRB Burst Dichotomy

Metzger, Brian D. and Sridhar, Navin and Margalit, Ben and Beniamini, Paz and Sironi, Lorenzo (2022) A Toy Model for the Time–Frequency Structure of Fast Radio Bursts: Implications for the CHIME/FRB Burst Dichotomy. Astrophysical Journal, 925 (2). Art. No. 135. ISSN 0004-637X. doi:10.3847/1538-4357/ac3b4a.

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We introduce a toy model for the time–frequency structure of fast radio bursts, in which the observed emission is produced as a narrowly peaked intrinsic spectral energy distribution sweeps down in frequency across the instrumental bandpass as a power law in time. Though originally motivated by emission models that invoke a relativistic shock, the model could in principle apply to a wider range of emission scenarios. We quantify the burst’s detectability using the frequency bandwidth over which most of its signal-to-noise ratio is accumulated. We demonstrate that, by varying just a single parameter of the toy model—the power-law index β of the frequency drift rate—one can transform a long (and hence preferentially time-resolved) burst with a narrow time-integrated spectrum into a shorter burst with a broad power-law time-integrated spectrum. We suggest that source-to-source diversity in the value of β could generate the dichotomy between burst duration and frequency-bandwidth recently found by CHIME/FRB. In shock models, the value of β is related to the radial density profile of the external medium, which, in light of the preferentially longer duration of bursts from repeating sources, may point to diversity in the external environments surrounding repeating versus one-off FRB sources.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Metzger, Brian D.0000-0002-4670-7509
Sridhar, Navin0000-0002-5519-9550
Margalit, Ben0000-0001-8405-2649
Beniamini, Paz0000-0001-7833-1043
Sironi, Lorenzo0000-0002-1227-2754
Alternate Title:A Toy Model for the Time-Frequency Structure of Fast Radio Bursts: Implications for the CHIME Burst Dichotomy
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 25; revised 2021 November 16; accepted 2021 November 17; published 2022 February 1. We thank Shami Chatterjee and Ziggy Pleunis for helpful conversations. B.D.M. acknowledges support from the National Science Foundation (grant No. GG016244). The research of P.B. was funded by the Gordon and Betty Moore Foundation through Grant GBMF5076. B.M. is supported by NASA through the NASA Hubble Fellowship grant #HST-HF2-51412.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. L.S. acknowledges support from the Cottrell Scholars Award and NASA 80NSSC18K1104.
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF5076
NASA Hubble FellowshipHST-HF2-51412.001-A
NASA Einstein FellowshipUNSPECIFIED
Subject Keywords:Radio transient sources
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Radio transient sources (2008)
Record Number:CaltechAUTHORS:20220203-318323000
Persistent URL:
Official Citation:Brian D. Metzger et al 2022 ApJ 925 135
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113258
Deposited By: George Porter
Deposited On:03 Feb 2022 21:42
Last Modified:03 Feb 2022 21:42

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