Astronomers using the CHIME (Canadian Hydrogen Intensity Mapping Experiment) and FAST (Five-hundred-meter Aperture Spherical radio Telescope) telescopes have detected an extremely intense radio burst emanating from SGR 1935+2154, a magnetar located 4,400 parsecs (14,351 light-years) away in the constellation of Vulpecula.
An artist’s impression of the SGR 1935+2154 magnetar in outburst, showing complex magnetic field structure and beamed emission. Image credit: McGill University Graphic Design Team.
Fast radio bursts (FRBs) are mysterious and rarely detected bursts of radio waves from space.
The first FRB was discovered in 2007, although it was actually observed some six years earlier, in archival data from a pulsar survey of the Magellanic Clouds.
FRBs have durations of milliseconds and exhibit the characteristic dispersion sweep of radio pulsars.
These events emit as much energy in one millisecond as the Sun emits in 10,000 years, but the physical phenomenon that causes them is unknown.
One theory hypothesized FRBs to be extragalactic magnetars — highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays.
“So far, all of the FRBs that telescopes like CHIME have picked up were in other galaxies, which makes them quite hard to study in great detail,” said co-author Ziggy Pleunis, a Ph.D. student in the Department of Physics at McGill University.
“Moreover, the magnetar theory was not supported by observations of magnetars in our own Galaxy as they were found to be far less intense than the energy released by extragalactic FRBs until now.”
Using the CHIME radio telescope, Pleunis and colleagues detected the bright millisecond-duration radio burst, dubbed FRB 200428, from the SGR 1935+2154 magnetar.
The intensity of the event was three orders of magnitude higher than the burst energy of any radio-emitting magnetar detected thus far, lending weight to the theory that magnetars are at the origin of at least some FRBs.
“We calculated that such an intense burst coming from another galaxy would be indistinguishable from some FRBs, so this really gives weight to the theory suggesting that magnetars could be behind at least some FRBs,” said co-author Pragya Chawla, a Ph.D. student in the Department of Physics at McGill University.
“Given the large gaps in energetics and activity between the brightest and most active FRB sources and what is observed for magnetars, perhaps younger, more energetic and active magnetars are needed to explain all FRB observations,” said co-author Dr. Paul Scholz, a researcher in the Dunlap Institute of Astronomy and Astrophysics at the University of Toronto.
In a separate study, University of Nevada astronomer Bing Zhang and colleagues used the FAST radio telescope to conduct multiband observations of SGR J1935+2154.
“We now know that the most magnetized objects in the Universe, the so-called magnetars, can produce at least some or possibly all FRBs in the Universe,” Dr. Zhang said.
The findings were published in two papers in the November 5, 2020 issue of the journal Nature.
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B. Andersen et al. 2020. A bright millisecond-duration radio burst from a Galactic magnetar. Nature 587, 54-58; doi: 10.1038/s41586-020-2863-y
L. Lin et al. 2020. No pulsed radio emission during a bursting phase of a Galactic magnetar. Nature 587, 63-65; doi: 10.1038/s41586-020-2839-y
