Fast radio bursts, or FRBs, are powerful, bright emissions of radio waves ranging from a fraction of a millisecond to a few thousandths of a second, each producing energy equivalent to the annual output of the Sun.
Emissions associated with FRB 20201124A occurred for 82 hours over 54 days in the spring of 2021, making it one of the most energetic fast radio bursts. It was visible through the world’s largest radio telescope – the five hundred-meter aperture spherical radio telescope, or FAST.
During the first 36 days, the study team was surprised to see irregular, short duration differences in the Faraday rotation scale, which measures magnetic field strength and particle density in the vicinity of FRB 20201124A. A larger spin scale means the magnetic field near the source of the radio burst is stronger, more intense, or both, and a smaller scale means the opposite, study co-author and astrophysicist Bing Zhang said via email.
“This does not reflect the onset (of life) of the FRB,” said Zhang, founding director of the Center for Astrophysics at the University of Nevada, Las Vegas. “The FRB source has been there for a long time but has been asleep most of the time. It wakes up sometimes (this time for 54 days) and emits a lot of explosions.”
The scales rose up and down during that time period, then stopped for the last 18 days before the FRB subsided — “indicating that the magnetic field strength and/or intensity along the line-of-sight in the vicinity of the FRB source varies with time.” “It indicates that the FRB source environment is evolving dynamically, with rapid change in magnetic fields, density, or both.”
“I’m like filming a FRB source environment, and our film revealed a complex, dynamically evolving magneto-environment that had never been imagined before,” Zhang said in a press release.
The researchers found that the complex magneto-environment of the radio explosion lies within an astronomical unit (the distance between the Earth and the Sun) from its source.
They also discovered that the explosion originated from a narrow, metal-rich spiral galaxy similar in size to the Milky Way, using the 10-meter Keck telescopes in Mauna Kea, Hawaii. The source of the radio burst is located between the spiral arms of the galaxy where no significant star formation occurs, making it unlikely that the origin was solely a magnetar, according to nature study co-author Sobu Dong, associate professor at the Kavli Institute for Astronomy and Astrophysics. at Peking University.
“Such an environment is not directly predictable for an isolated magnetar,” Zhang said in a press release. “There might be something else near the FRB engine, maybe it’s a binary companion.”
The authors said the modeling study should encourage further research on fast radio burst signals from Be star/X-ray binaries.
“These notes brought us back to the drawing board,” Zhang said. “FRBs are clearly more mysterious than we imagined. More multi-wavelength observational campaigns are needed to reveal the nature of these things.”
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