Puzzling new features captured in cosmic FRB signals

Sep. 22 () –

Unexpected observations of a series of fast radio bursts (FRBs) challenge prevailing understanding of physical nature and the central engine of these strange cosmic signals.

FRBs are millisecond-long cosmic explosions that produce energy equivalent to the sun’s annual output. More than 15 years after pulses of electromagnetic radio waves were first discovered in deep space, their puzzling nature continues to amaze scientists, and newly published research it only deepens the mystery that surrounds them.

The observations subject to a new investigation were made in late spring 2021 using the huge 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 fast radio burst source. activate FRB call. 20201124A.

“This is the largest sample of FRB data with polarization information from a single source,” said Lee. it’s a statement.

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

“These observations took us back to the drawing board,” said Zhang, who also serves as the founding director of the Nevada Center for Astrophysics at UNLV (University of Nevada, Las Vegas). “It is clear that FRBs are more mysterious than we imagined. More multi-wavelength observing campaigns are needed to further reveal the nature of these objects.”

What makes the latest observations surprise scientists are the irregular and brief variations in the so-called “Faraday spin measure,” which is the strength of the magnetic field and the density of particles in the vicinity of the FRB source. Variations rose and fell during the first 36 days of observation and suddenly stopped during the last 18 days before the source was extinguished.

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

To observe the FRB’s host galaxy, the team also made use of the 10m Keck Telescopes located on Mauna Kea in Hawaii. Zhang says that young magnetars are thought to reside in 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 Via. milky The location of FRB is in a region where there is no significant star formation activity.

“This location is inconsistent with a young magnetar core engine formed during an extreme outburst, such as a long gamma-ray burst or a superluminous supernova, widely speculated progenitors of active FRB engines,” Dong said.

The study has been published in Nature and includes 74 co-authors from 30 institutions.