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Faraday conversion and magneto-ionic variations in fast radio bursts

Vedantham, H. K. and Ravi, V. (2019) Faraday conversion and magneto-ionic variations in fast radio bursts. Monthly Notices of the Royal Astronomical Society: Letters, 485 (1). L78-L82. ISSN 1745-3925. https://resolver.caltech.edu/CaltechAUTHORS:20190625-161754998

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Abstract

The extreme, time-variable Faraday rotation observed in the repeating fast radio burst (FRB) 121102 and its associated persistent synchrotron source demonstrates that some FRBs originate in dense, dynamic, and possibly relativistic magneto-ionic environments. Besides rotation of the linear polarization vector (Faraday rotation), such media can generally convert linear to circular polarization (Faraday conversion). We use non-detection of Faraday conversion, and the temporal variation in Faraday rotation and dispersion in bursts from FRB 121102 to constrain models where the progenitor inflates a relativistic nebula (persistent source) confined by a cold dense medium (e.g. supernova ejecta). We find that the persistent synchrotron source, if composed of an electron–proton plasma, must be an admixture of relativistic and non-relativistic (Lorentz factor γ < 5) electrons. Furthermore, we independently constrain the magnetic field in the cold confining medium, which provides the Faraday rotation, to be between 10 and 30 mG. This value is close to the equipartition magnetic field of the confined persistent source implying a self-consistent and overconstrained model that can explain the observations.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/mnrasl/slz038DOIArticle
https://arxiv.org/abs/1812.07889arXivDiscussion Paper
ORCID:
AuthorORCID
Vedantham, H. K.0000-0002-0872-181X
Ravi, V.0000-0002-7252-5485
Additional Information:© 2019 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 (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) Accepted 2019 March 7. Received 2019 March 7; in original form 2019 January 16. The authors thank (i) Andrei Gruzinov and Eli Waxman for discussions on the implications of Faraday conversion, (ii) Eli Waxman for commenting on the manuscript, (iii) Jason Hessels for discussions regarding observational aspects of FRB 121102, (iv) Dongzi Li for pointing out an error in our application of Faraday conversion in an earlier version of the manuscript, and (v) the organizers of the 2018 Schwartz/Reisman Institute for Theoretical Physics workshop on Fast Radio Bursts for their hospitality. Numerical computations used SCIPY, NUMPY, PYTHON2.7, and PYTHON3.0. MATPLOTLIB was used to render the figures.
Subject Keywords:polarization, radiative transfer, radio continuum: general
Issue or Number:1
Record Number:CaltechAUTHORS:20190625-161754998
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190625-161754998
Official Citation:H K Vedantham, V Ravi, Faraday conversion and magneto-ionic variations in fast radio bursts, Monthly Notices of the Royal Astronomical Society: Letters, Volume 485, Issue 1, May 2019, Pages L78–L82, https://doi.org/10.1093/mnrasl/slz038
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96709
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:26 Jun 2019 14:39
Last Modified:03 Oct 2019 21:24

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