Ever since rapid radio bursts (FRBs) were first discovered over a decade ago, scientists have wondered what could generate these intense flashes of radio waves from outside our galaxy. In a gradual process of elimination, the field of possible explanations has narrowed as more information is gathered about FRBs – their duration, the frequencies of radio waves detected, etc.
Now, a team led by researchers at McGill University and members of the Canadian CHIME Fast Radio Burst collaboration has established that FRBs include radio waves at lower frequencies than ever before detected, a discovery that redraws the boundaries for theoretical astrophysicists trying to pinpoint the source of FRBs.
“We have detected rapid radio bursts up to 110 MHz where previously these bursts were only known up to 300 MHz,” explained Ziggy Pleunis, postdoctoral researcher in the McGill Department of Physics and senior research author recently. published in the Letters from the Astrophysical Journal. “This tells us that the region around the source of the bursts must be transparent to low frequency emission, whereas some theories suggest that any low frequency emission would be absorbed immediately and could never be detected.”
The study focused on an FRB source first detected in 2018 by the CHIME radio telescope in British Columbia. Known as FRB 20180916B, the source has gained special attention due to its relative proximity to Earth and the fact that it emits FRBs at regular intervals.
The research team combined the capabilities of CHIME with those of another radio telescope, LOFAR, or Low Frequency Array, in the Netherlands. The joint effort not only detected the remarkably low FRB frequencies, but also revealed a constant delay of about three days between the highest frequencies picked up by CHIME and the lower frequencies reaching LOFAR.
“This systematic delay excludes explanations of periodic activity which do not allow frequency dependence and thus brings us a few steps closer to understanding the origin of these mysterious bursts,” adds co-author Daniele Michilli, also postdoctoral researcher in the Department of Physics at McGill.
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