Astronomers reveal new – and puzzling – features of mysterious fast radio bursts

Technical rendering of the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in China. Credit: Jingchuan Yu

Fast radio bursts (FRBs) are millisecond-long cosmic blasts that each produce energy equivalent to the annual output of the Sun. More than 15 years after electromagnetic radio wave pulses were first detected in deep space, their bewildering nature continues to surprise scientists — and newly published research deepens the mystery surrounding them.

In the September 21 issue of the magazine temper natureunexpected new observations of a series of fast cosmic radio bursts by an international team of scientists — including UNLV astrophysicist Bing Zhang — challenging the prevailing understanding of the physical nature and central driver of FRBs.

Cosmic FRB observations were made in late spring 2021 using the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in China. The team led by Heng Xu, Kejia Lee and Subo Dong of Peking University and Weiwei Zhu of the National Astronomical Observatories in China, along with Zhang, detected 1,863 blasts in 82 hours over 54 days from an active fast radio burst source called FRB 20201124a.

“This is the largest sample of FRB data with polarization information from a single source,” Lee told me.

Recent observations of the fast radio burst from our Milky Way suggest that it originated from a magnetar, a dense, city-sized neutron star with an incredibly strong magnetic field. On the other hand, the origin of distant cosmic fast radio bursts is still unknown. Recent observations leave scientists wondering what they think they know about them.

“These observations brought us back to the drawing board,” said Zhang, who is also the founding director of UNLV’s Nevada Center for Astrophysics. “FRBs are clearly more mysterious than we imagined. More multi-wavelength observational campaigns are needed to reveal the nature of these things.”

What makes the recent observations surprising to scientists are the irregular and short variations of the so-called “Faraday spin scale,” the magnetic field strength and particle density in the vicinity of the FRB source. Variations went up and down during the first 36 days of monitoring and stopped abruptly for the last 18 days before the source was extinguished.

“I liken it to a movie shooting of the FRB source environment, and our film revealed a complex and dynamically evolving magneto-environment that had never been imagined before,” Zhang said. “Such an environment is not directly predictable for an isolated magnetar. There may be something else near the FRB engine, possibly a binary companion,” Zhang added.

To observe the FRB host galaxy, the team also used the 10-meter Keck telescopes located on Mauna Kea in Hawaii. Zhang says he thinks young magnetars live in the active star-forming regions of the star-forming galaxy, but the optical image of the host galaxy unexpectedly shows that the host galaxy is a barred, metallic spiral galaxy like our Milky Way. . The FRB site is located in an area where there is no significant star-forming activity.

“This location is inconsistent with a young centromagnetic drive formed during an intense explosion such as a long gamma-ray burst or ultra-bright supernova, which are widely expected predecessors to energetic FRBs,” Dong said.

The study, “Source of a Fast Radio Burst at a Complex Magnetized Site in a Tight Galaxy,” appeared Sept. 21 in the journal. temper nature It features 74 co-authors from 30 institutions. In addition to UNLV, Peking University, and the National Astronomical Observatories of China, collaborating institutions also include the Purple Mountain Observatory, the University of Yunnan, the University of California at Berkeley, the California Institute of Technology, Princeton University, the University of Hawaii, and other institutions from China, the United States, Australia, Germany and Israel.

Astronomers discover clues that reveal the secret of fast radio bursts

more information:
H. Xu et al., A fast radio burst source at a complex magnetized site in a narrow galaxy, temper nature (2022). DOI: 10.1038 / s41586-022-05071-8

Provided by University of Nevada, Las Vegas

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