New Repeating Fast Radio Bursts Discovered

The catalog of repeating fast radio bursts — brief bursts of radio waves traveling through space from unknown sources — has been doubled by the international Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME-FRB) Collaboration. The multi-institution team, which includes Carnegie Mellon University’s Mohit Bhardwaj, published their findings in The Astrophysical Journal.

“Fast radio bursts are one of astronomy’s greatest mysteries,” said Bhardwaj, who is a McWilliams Postdoctoral Fellow in the Department of Physics and part of Carnegie Mellon’s McWilliams Center for Cosmology. “Despite lasting only a few thousandths of a second, these extremely powerful radio blasts can travel vast cosmological distances and emit more energy than the sun does in a thousand years.”

Fast radio bursts (FRBs) come from origins far outside of the Milky Way. While it is thought that they are produced in the aftermath of a star’s death, their exact source is a mystery. Thousands of FRB sources have been observed, but most appear to burst only once. Until now, a mere 25 had been observed to burst multiple times.

The CHIME-FRB Collaboration developed a new clustering algorithm that uses various characteristics of FRBs to sift through data and identify which bursts were produced by the same source. Using this algorithm, the collaboration’s researchers discovered 25 new repeating sources, and 16 candidate sources — bringing the total of known repeating FRBs to 50.

Of the newly identified repeating FRB sources, most were relatively inactive with long intervals of time between bursts, and they were nearer to Earth. It’s possible that this means that FRB sources that are thought to be non-repeating may repeat, they just need to be observed for longer time periods. Understanding this could be key to identifying if repeating and non-repeating FRBs come from the same or different types of sources.

“While their origins are still a mystery, if we can identify the source of FRBs, we can gain new insights into the extreme astrophysical environments that give rise to these signals and the physical mechanisms responsible for their emission,” said Bhardwaj. “The bursts themselves hold great promise for cosmological studies. For each FRB, we can estimate the amount of ionized baryons its signal travels through on the way to Earth. No other known astrophysical probe can do that.”

The group’s discovery was made using the CHIME radio telescope. Radio telescopes observe radio waves, making them the only type of telescope that can observe FRBs. However, cosmological models show that FRBs could exist at other wavelengths.

Bhardwaj’s completed the work reported in the current paper as a doctoral student at McGill University in Montreal. As a postdoctoral researcher at Carnegie Mellon, he continues to be a member of the CHIME/FRB Collaboration and is part of the group identifying potential host galaxies for FRBs, which is a crucial step toward uncovering the origins of the phenomena.

The CHIME project is co-led by the University of British Columbia, McGill University, University of Toronto and the Dominion Radio Astrophysical Society with collaborating institutions across North America.