Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio flashes probably arriving from far outside the Milky Way1,2. This phenomenon was discovered at radio frequencies near 1.4 gigahertz and so far has been observed in one case3 at as high as 8 gigahertz, but not at below 700 megahertz in spite of substantial searches at low frequencies4,5,6,7. Here we report detections of 13 FRBs at radio frequencies as low as 400 megahertz, on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) using the CHIME/FRB instrument8. They were detected during a telescope pre-commissioning phase, when the sensitivity and field of view were not yet at design specifications. Emission in multiple events is seen down to 400 megahertz, the lowest radio frequency to which the telescope is sensitive. The FRBs show various temporal scattering behaviours, with the majority detectably scattered, and some apparently unscattered to within measurement uncertainty even at our lowest frequencies. Of the 13 reported here, one event has the lowest dispersion measure yet reported, implying that it is among the closest yet known, and another has shown multiple repeat bursts, as described in a companion paper9. The overall scattering properties of our sample suggest that FRBs as a class are preferentially located in environments that scatter radio waves more strongly than in the diffuse interstellar medium in the Milky Way.
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The raw data used in this publication are available at https://chime-frb-open-data.github.io/.
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We are grateful for the help we received from the Dominion Radio Astrophysical Observatory, operated by the National Research Council Canada. The CHIME/FRB Project is funded by a grant from the Canada Foundation for Innovation 2015 Innovation Fund (Project 33213), as well as by the Provinces of British Columbia and Québec, and by the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto. Additional support was provided by the Canadian Institute for Advanced Research (CIFAR), McGill University and the McGill Space Institute via the Trottier Family Foundation, and the University of British Columbia. The Dunlap Institute is funded by an endowment established by the David Dunlap family and the University of Toronto. Research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research & Innovation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. P.C. is supported by an FRQNT Doctoral Research Award and a Mitacs Globalink Graduate Fellowship. M.D. acknowledges support from CIFAR, Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery and Accelerator Grants, and from FRQNT Centre de Recherche en Astrophysique du Québec (CRAQ). B.M.G. acknowledges the support of the NSERC through grant RGPIN-2015-05948, and the Canada Research Chairs program. A.S.H. is partly supported by the Dunlap Institute. V.M.K. holds the Lorne Trottier Chair in Astrophysics & Cosmology and a Canada Research Chair and receives support from an NSERC Discovery Grant and Herzberg Award, from an R. Howard Webster Foundation Fellowship from CIFAR, and CRAQ. C.M. is supported by a NSERC Undergraduate Research Award. J.M.-P. is supported by the MIT Kavli Fellowship in Astrophysics and a FRQNT postdoctoral research scholarship. M.M. is supported by a NSERC Canada Graduate Scholarship. Z.P. is supported by a Schulich Graduate Fellowship. S.M.R. is a CIFAR Senior Fellow and is supported by the NSF Physics Frontiers Center award 1430284. P.S. is supported by a DRAO Covington Fellowship from the National Research Council Canada. FRB research at UBC is supported by an NSERC Discovery Grant and by CIFAR.
The authors declare no competing interests.
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The CHIME/FRB Collaboration. Observations of fast radio bursts at frequencies down to 400 megahertz. Nature 566, 230–234 (2019). https://doi.org/10.1038/s41586-018-0867-7
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