title: Dense magnetized plasma associated with a fast radio burst.
abstract: Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy.
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada.|Canadian Institute for Advanced Research, CIFAR Program in Cosmology and Gravity, Toronto, Ontario M5G 1Z8, Canada.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Masui
authors.affiliation: McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Hsiu-Hsien
authors.initials: HH
authors.lastname: Lin
authors.affiliation: Astrophysics and Cosmology Research Unit, School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4001, South Africa.|National Institute for Theoretical Physics (NITheP), KZN node, Durban 4001, South Africa.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Sievers
authors.affiliation: Department of Physics, University of Wisconsin, Madison, Wisconsin 53706-1390, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Anderson
authors.affiliation: Academia Sinica Institute of Astronomy and Astrophysics, 11F Astro-Math Building, AS/NTU 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.
authors.forename: Tzu-Ching
authors.initials: TC
authors.lastname: Chang
authors.affiliation: National Astronomical Observatories, Chinese Academy of Science, 20A Datun Road, Beijing 100012, China.|Center of High Energy Physics, Peking University, Beijing 100871, China.
authors.forename: Xuelei
authors.initials: X
authors.lastname: Chen
authors.affiliation: Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics, and Computer Science, University of KwaZulu-Natal, Durban 4001, South Africa.
authors.forename: Apratim
authors.initials: A
authors.lastname: Ganguly
authors.affiliation: Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, Ontario M5S 3H4, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Jarvis
authors.affiliation: Academia Sinica Institute of Astronomy and Astrophysics, 11F Astro-Math Building, AS/NTU 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.|Department of Physics, National Sun Yat-Sen University No. 70, Lianhai Road, Gushan District, Kaohsiung City 804, Taiwan.
authors.forename: Cheng-Yu
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: National Astronomical Observatories, Chinese Academy of Science, 20A Datun Road, Beijing 100012, China.
authors.forename: Yi-Chao
authors.initials: YC
authors.lastname: Li
authors.affiliation: Academia Sinica Institute of Astronomy and Astrophysics, 11F Astro-Math Building, AS/NTU 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Liao
authors.affiliation: Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA.
authors.forename: Maura
authors.initials: M
authors.lastname: McLaughlin
authors.affiliation: Canadian Institute for Advanced Research, CIFAR Program in Cosmology and Gravity, Toronto, Ontario M5G 1Z8, Canada.|Canadian Institute for Theoretical Astrophysics, 60 St George Street, Toronto, Ontario M5S 3H8, Canada.|Perimeter Institute, 31 Caroline Street, Waterloo N2L 2Y5, Canada.
authors.forename: Ue-Li
authors.initials: UL
authors.lastname: Pen
authors.affiliation: McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Peterson
authors.affiliation: McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Roman
authors.affiliation: Department of Physics, University of Wisconsin, Madison, Wisconsin 53706-1390, USA.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Timbie
authors.affiliation: McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, USA.|Astrophysics and Cosmology Research Unit, School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4001, South Africa.
authors.forename: Tabitha
authors.initials: T
authors.lastname: Voytek
authors.affiliation: Indian Institute of Science Education and Research Mohali, Knowledge City, Sector 81, SAS Nagar, Manauli, PO 140306, India.
authors.forename: Jaswant K
authors.initials: JK
authors.lastname: Yadav