The unique wide-field view of a Canadian observatory allowed a large team to pinpoint a possible source of a mysterious “fast radio burst” (FRB) in our Milky Way.
The Canadian-led team used the Canadian Hydrogen Intensity Mapping Experiment (CHIME) to detect an intense radio burst that may be associated with a magnetar, or a star that has a very strong magnetic field. Magnetars are also neutron stars, which are the core remnants of very massive stars that exploded as supernovas.
CHIME, which is based at the Dominion Radio Astrophysical Observatory near Penticton, B.C., has four antennas that receive radio waves from space. The team says the X-ray burst CHIME detected, along with the FRB, gives weight to the idea that a magnetar outburst was responsible.
“Most radio telescopes in the world can only observe a small area of the sky, about the size of the full moon, at any given time,” study co-author Pragya Chawla, a senior PhD student in physics at McGill University in Montreal, told SpaceQ.
“However,” Chawla added, “CHIME observes an area that is about five hundred times larger. This allows us to monitor all magnetars located in the northern sky every day, which greatly boosts our chances of detecting a burst as rare as this one.”
The team, which comprised about 50 people, spotted the FRB on April 28. It was the first such detection of an intense radio burst in our galaxy, Chawla said. The observations also allowed researchers to see an associated X-ray burst for the first time, due to the explosion’s relative proximity to our planet. “All other known FRBs are inferred to be located outside the Milky Way,” Chawla added.
FRBs were first found roughly 10 years ago, and their origin stories have been elusive. Astronomers first thought FRBs were isolated events, but through ongoing observations they discovered FRBs do reoccur in the same areas of the sky from time to time.
But where the FRBs come from has been a mystery. Several theories have been proposed, with the magnetar being one of those ideas due to its ability to send out huge bursts of energy. In some cases, FRBs produce events that are more intense than what Earth’s sun can generate in millions or even billions of years.
While the new event gives more credence that FRBs come from magnetars, the link isn’t quite established yet. “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 Paul Scholz, a co-author and NSERC fellow at University of Toronto’s Dunlap Institute of Astronomy and Astrophysics, in a statement from McGill.
One of the main observing challenges faced was that the FRB was not directly overhead CHIME’s detectors, meaning that the thicker layers of Earth’s atmosphere closer to the horizon interfered somewhat with understanding how bright the burst was.
“Members of our team then modelled the sensitivity of CHIME at the source location, and we found that the burst was over a thousand times brighter than any magnetar burst seen before,” Chawla said.
CHIME continues the search for FRBs, and what the researchers are hoping for is to see a similar event outside of the Milky Way that would pinpoint its location at a magnetar. What they would have to see is an extragalactic FRB at the same time as an X-ray burst. “This would confirm that magnetars give birth to the extragalactic FRBs that we have been seeing with CHIME,” Chawla said.
A study based on the research was published in Nature, led by Bridget Andersen, a graduate student at McGill.