An illustration depicting a FRB (not the one detailed in the new study).

Fast radio bursts: Study reveals details of origin

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More than 15 years after the discovery of fast radio bursts, new research has unraveled and deepened the mystery of the origin of these deep space phenomena.

A fast radio burst (FRB) is a bright, powerful emission of radio waves ranging from a fraction of a millisecond to a few milliseconds, each producing an energy equivalent to the Sun’s annual output.

Recent research has shown that some FRBs originate from magnetars, which are neutron stars with extremely strong magnetic fields. Fast radio bursts found in the Milky Way are associated with magnetars, according to a 2020 study.

But scientists have yet to pinpoint the origin of cosmic FRBs, which are billions of light-years away. That’s a conundrum that led an international team of scientists to see what it could get from an active fast radio burst source outside our galaxy called FRB 20201124A, a source of nearly 1,900, according to a study published Sept. 21 in the journal Nature. What was learned from the observations of the sub-burst.

The emission associated with FRB 20201124A occurred 82 hours in 54 days in spring 2021, making it one of the most active fast radio bursts known. It is visible through the world’s largest radio telescope, China’s Five-hundred-meter Aperture Spherical Radio Telescope (FAST).

During the first 36 days, the team was surprised to find irregular, short-duration changes in the Faraday spin measurement, which measures the magnetic field strength and particle density around FRB 20201124A. Astrophysicist Bing Zhang, co-author of the study, said by email that larger rotation measurements mean stronger, denser, or both magnetic fields near the source of the radio burst, while smaller measurements do the opposite. .

“This does not reflect the beginning of the FRB (lifetime),” said Zhang, founding director of the Center for Astrophysics at the University of Nevada, Las Vegas. “The FRB source has been around for a long time, but is dormant most of the time. It wakes up occasionally (54 days this time) and sends out a lot of bursts.”

These measures fluctuate up and down during that time and then stop for the last 18 days before the FRB decays — “indicating that the magnetic field strength and/or density along the line-of-sight near the FRB source varies over time,” Zhang added. “This suggests that the environment of the FRB source is dynamically evolving, with rapidly changing magnetic fields or densities or both.”

“I equate it with taking a film of the environment around the FRB source, and our film reveals a complex, dynamically evolving, magnetized environment that was never imagined before,” Zhang said in a news release.

A physical model made by another research team based on observations of FRB 20201124A suggests that the FRB comes from a binary star system about 8,480 light-years away, containing a magnetar and a Be star, the ratio of which is based on a Sept. 21 release. Another study in the journal Nature Communications, Sun.

The researchers found that the radio burst’s complex magnetized environment is about an astronomical unit (the distance between the Earth and the sun) from its source.

Using the 10-meter Keck telescope on Mauna Kea, Hawaii, they also found that the outburst originated in a barred spiral galaxy that is metal-rich and similar in size to the Milky Way. According to Su Bodong, co-author of the Nature study and associate professor at the Kavli Institute for Astronomy and Astrophysics, the source of the radio burst is located between the spiral arms of the Milky Way, where no apparent star formation has occurred, so it is unlikely to be just a magnetar . at Peking University.

“For an isolated magnetar, this environment is not directly expected,” Zhang said in a news release. “There might be something else near the FRB engine, possibly a binary companion.”

The authors say that modeling studies should encourage further searches for FRB signals from Be stars/X-ray binaries.

“These observations bring us back to the drawing board,” Zhang said. “It is clear that FRBs are more mysterious than we thought. More multi-wavelength observational campaigns are needed to further reveal the nature of these objects.”

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