Fast radio blast: Studies reveal 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 sources of these phenomena in deep space.

Fast radio bursts, or FRBs, are bright and powerful emissions of radio waves ranging from a fraction of a millisecond to a few milliseconds, each producing energy equivalent to the annual output of the sun.

Recent research has suggested that some FRBs come from magnetars, which are neutron stars with extremely powerful magnetic fields. According to a 2020 study, a fast radio blast found in the Milky Way was associated with a magnetar.

But scientists have not yet pinpointed the origins of cosmological FRBs, which are billions of light years away. It’s a dilemma that has led an international team of scientists to see what they could learn from observations of nearly 1,900 flashes from an active fast radio burst source outside our own galaxy called FRB 20201124A, according to a study published Sept. 21 in the journal Nature. .

The emissions associated with FRB 20201124A occurred for 82 hours over 54 days in the spring of 2021, making it one of the most active fast radio bursts known. It was visible through the largest radio telescope in the world: the China-based five-hundred-meter aperture spherical radio telescope, or FAST.

During the first 36 days, the study team was surprised to see irregular and short-lived variations in Faraday’s rotation measurement, which measures magnetic field strength and particle density around FRB 20201124A. A larger rotation measurement means that the magnetic field near the source of the radio blast is stronger, denser, or both, and a smaller measurement means the opposite, study co-author and astrophysicist Bing Zhang said via email. .

“This does not reflect the beginning of the FRB (lifespan),” said Zhang, the 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 it has been inactive most of the time. From time to time it wakes up (this time for 54 days) and emits many bursts.

Measurements increased and decreased during that time period, and then stopped in the last 18 days before the FRB subsided, “suggesting that the strength and / or density of the magnetic field along the line of sight near the source of FRBs vary over time, “Zhang added.” It suggests that the FRB source environment is dynamically evolving, with magnetic fields or densities changing rapidly or both. ”

“I would compare it to making a film about the surroundings of an FRB source, and our film revealed a complex, dynamically evolving magnetized environment that had never been imagined before,” Zhang said in a press release.

A physical model that a different team of researchers made based on the observations of FRB 20201124A proposes that the FRB comes from a binary system about 8,480 light years away containing a magnetar and a star Be, a hotter and larger star and that rotates faster than the sun, according to a separate study published Sept. 21 in the journal Nature Communications.

The researchers found that the complex magnetized environment of the radio blast lies within an astronomical unit (the distance between the Earth and the sun) from its source.

They also found that the explosion originated from a metal-rich, barred spiral galaxy similar in size to the Milky Way, using the 10-meter Keck telescopes in Mauna Kea, Hawaii. The source of the radio blast is located between the spiral arms of the galaxy where no significant star formation is occurring, making it less likely that the origin is exclusively a magnetar, according to study co-author in Nature Subo Dong, professor. associated with the Kavli Institute for Astronomy and Astrophysics at Peking University.

“Such an environment is not directly intended for an isolated magnetar,” Zhang said in a news release. “Something else could be in the vicinity of the FRB engine, perhaps a binary companion.”

The modeling study should encourage further research into fast-burst radio signals from B-star / X-ray binaries, the authors said.

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

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