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Over a thousand cosmic explosions traced to mysterious repeating fast radio burst

Using China’s Five-hundred-meter Aperture Spherical radio Telescope, or FAST, researchers detected 1,652 bursts over the course of 47 days, between August 29 and October 29, 2019. This is the largest set of fast radio burst events so far.

A study detailing these findings published on Wednesday in the journal Nature.

Fast radio bursts, or FRBs, are millisecond-long emissions of radio waves in space, and astronomers have been able to trace some radio bursts back to their home galaxies. Scientists have yet to determine the actual cause of the flashes. But the short bursts can produce a year’s worth of our sun’s total energy output.

Individual radio bursts emit once and don’t repeat. But repeating fast radio bursts are known to send out short, energetic radio waves multiple times. FRB 121102 has been known as a repeating fast radio burst since 2016.

During testing of the FAST telescope as it was being commissioned, researchers noticed FRB 121102 was frequently flaring and sending out radio signals, with a varying cadence. A total of 122 bursts were recorded during the peak hour, making it the highest rate ever for any fast radio burst. The 1,652 individual bursts occurred over a total of 59.5 hours spread across 47 days.

“This was the first time that one FRB source was studied in such great detail,” said study coauthor Bing Zhang, an astrophysicist and distinguished professor at the University of Nevada, Las Vegas, in a statement. “The large burst set helped our team hone in like never before on the characteristic energy and energy distribution of FRBs, which sheds new light on the engine that powers these mysterious phenomena.”

The energy of the signals “severely constrains the possibility that FRB 121102 comes from an isolated compact object,” said study coauthor Wang Pei, an assistant professor from the National Astronomical Observatories of the Chinese Academy of Sciences, in a statement.

This illustration shows a "river" of bursts from a galaxy as recorded by the FAST telescope. The burst count and energies are shown in histograms, mimicking the painting "A Vast Land" by Wang Ximeng of the Song Dynasty.

While some people favor the idea that aliens could be the source of these bursts, scientists are leaning toward black holes or hyper-magnetized neutron stars called magnetars.

Magnetars are dense stars, about the size of a city like Chicago or Atlanta, with the strongest magnetic fields found in the universe. Scientists think the bursts could originate from the magnetic field of magnetars.

FRB 121102 was the first repeating fast radio burst to be traced back to its source, linked back to a small dwarf galaxy more than 3 billion light-years away in 2017. Researchers also detected a pattern within the burst in 2020. During this cyclical pattern, radio bursts are emitted during a 90-day window, followed by a silent period of 67 days. This pattern repeats every 157 days.

Previous observations showed that usually when they repeat, it’s sporadic or in a cluster.

With this new impressive set of activity from FRB 121102, researchers can better understand the energy associated with these flashes. This could help scientists learn more about the potential source of fast radio bursts.

Fast radio bursts were only discovered in 2007, followed by the discovery that some of them can repeat in 2016. Now, researchers know they can have patterns as well.

This illustration shows FAST catching a real pulse from FRB 121102.
The Commensal Radio Astronomy FAST Survey has helped find six new fast radio bursts, including a repeating one like FRB 121102.

“As the world’s largest antenna, FAST’s sensitivity proves to be conducive to revealing intricacies of cosmic transients, including FRBs,” said lead study author Li Di, a professor at the National Astronomical Observatories of the Chinese Academy of Sciences, in a statement.

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