Home Radio waves Astronomers reveal new – and puzzling – characteristics of mysterious fast radio bursts

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

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Fast radio bursts (FRBs) are one-millisecond cosmic explosions that each produce the energy equivalent of the sun’s annual output. More than 15 years after the discovery of pulses of electromagnetic radio waves in deep space, their puzzling nature continues to surprise scientists – and newly published research only deepens the mystery surrounding them.

In the September 21 issue of the journal Nature, unexpected new observations of a series of cosmic radio bursts by an international team of scientists – including UNLV astrophysicist Bing Zhang – challenge the current understanding of the physical nature and central driver of FRBs.

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

“This is the largest sample of FRB data with bias information from a single source,” Lee said.

Recent observations of a fast radio burst from our galaxy, the Milky Way, suggest that it originated from a magnetar, which is a dense, city-sized neutron star with an incredibly strong magnetic field. The origin of very distant cosmological fast radio bursts, on the other hand, remains unknown. And the latest sightings have scientists wondering what they thought they knew about them.

“These observations took us back to the drawing board,” said Zhang, who is also the founding director of UNLV’s Nevada Center for Astrophysics. “It is clear that FRBs are more mysterious than we imagined. Further multi-wavelength observation campaigns are needed to further reveal the nature of these objects.

What makes the latest observations surprising to scientists are the irregular and short-lived variations in the so-called ‘Faraday rotation measure’, which is the strength of the magnetic field and the density of particles near the source. FRB. The variations rose and fell during the first 36 days of observation and stopped abruptly during the last 18 days before the source was extinguished.

“I liken it to shooting a movie about the surroundings of an FRB source, and our movie revealed a complex, dynamically changing magnetized environment that had never been imagined before,” Zhang said. “Such an environment is not directly expected for an isolated magnetar. Something else could be near the FRB engine, possibly a binary companion,” Zhang added.

To observe the FRB’s host galaxy, the team also used the 10m Keck Telescopes located at Mauna Kea in Hawaii. Zhang says young magnetars are thought to reside in the active star-forming regions of a star-forming galaxy, but the optical image of the host galaxy shows that – unexpectedly – the host galaxy is a metal-rich barred spiral galaxy like our Milky Way. The FRB location is in a region where there is no significant star formation activity.

“This location is inconsistent with a young central magnetar motor formed during an extreme explosion such as a long burst of gamma rays or a superluminous supernova, widely speculated progenitors of active FRB motors,” Dong said.

Posting details

The study, “A fast radio burst source at a complex magnetized site in a barred galaxy», published on September 21 in the newspaper Nature and includes 74 co-authors from 30 institutions. Besides UNLV, Peking University and the National Astronomical Observatories of China, collaborating institutions also include Purple Mountain Observatory, Yunnan University, UC Berkeley, Caltech, Princeton University, University of Hawaii and other institutions in China, the United States, Australia, Germany and Israel.