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Radiation forces constrain the FRB mechanism

Kumar, Pawan and Lu, Wenbin (2020) Radiation forces constrain the FRB mechanism. Monthly Notices of the Royal Astronomical Society, 494 (1). pp. 1217-1228. ISSN 0035-8711. doi:10.1093/mnras/staa801.

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We provide constraints on fast radio burst (FRB) models by careful considerations of radiation forces associated with these powerful transients. We find that the induced Compton scatterings of the coherent radiation by electrons/positrons accelerate particles to very large Lorentz factors (LFs) in and around the source of this radiation. This severely restricts those models for FRBs that invoke relativistic shocks and maser-type instabilities at distances less than about 10¹³ cm of the neutron star. Radiation travelling upstream, in these models, forces particles to move away from the shock with an LF larger than the LF of the shock front. This suspends the photon generation process after it has been operating for less than ∼0.1 ms (observer frame duration). We show that masers operating in shocks at distances larger than 10¹³ cm cannot simultaneously account for the burst duration of 1 ms or more and the observed ∼GHz frequencies of FRBs without requiring an excessive energy budget (>10⁴⁶ erg); the energy is not calculated by imposing any efficiency consideration, or other details, for the maser mechanism, but is entirely the result of ensuring that particle acceleration by induced Compton forces upstream of the shock front does not choke off the maser process. For the source to operate more or less continuously for a few ms, it should be embedded in a strong magnetic field – cyclotron frequency ≫ wave frequency – so that radiation forces do not disperse the plasma and shut off the engine.

Item Type:Article
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URLURL TypeDescription Paper
Lu, Wenbin0000-0002-1568-7461
Additional Information:© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 March 19. Received 2020 March 9; in original form 2019 December 9. Published: 24 March 2020. We thank the referee, Roger Blandford, for helpful comments and suggestions. WL acknowledges useful discussions with Lorenzo Sironi and Brian Metzger on the physics of synchrotron instability and with Ben Margalit on wind nebulae near magnetars, and we thank Bing Zhang for comments and suggestions. WL was supported by the David and Ellen Lee Fellowship at Caltech.
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Subject Keywords:masers – radiation mechanisms: non-thermal – methods: analytical – stars: magnetars
Issue or Number:1
Record Number:CaltechAUTHORS:20200611-073037234
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Official Citation:Pawan Kumar, Wenbin Lu, Radiation forces constrain the FRB mechanism, Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 1, May 2020, Pages 1217–1228,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103836
Deposited By: Tony Diaz
Deposited On:11 Jun 2020 15:50
Last Modified:16 Nov 2021 18:25

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