Fast radio bursts (FRBs) are millisecond-long cosmic explosions, each of which produces energy equivalent to the annual power of the Sun. More than 15 years after electromagnetic radio wave pulses were first detected in deep space, their intricate nature continues to amaze scientists, and recently published studies only exacerbate the mystery surrounding them.
In the issue of the magazine on September 21 Natureunexpected new observations of a series of cosmic fast radio bursts by an international team of scientists, including UNLV astrophysicist Bing Zhang, challenge the prevailing understanding of the physical nature and central engine of the FRB.
FRB space observations were made in late spring 2021 with the 500m Aperture Massive Spherical Radio Telescope (FAST) in China. A team led by Heng Xu, Kejia Li, Subo Dong of Peking University and Weiwei Zhu of China’s National Astronomical Observatory, along with Zhang, detected 1,863 flares in 82 hours over 54 days from an active source of fast radio bursts called FRBs. 20201124A.
“This is the largest sample of FRB data with polarization information from a single source,” Li said.
Recent observations of a fast radio burst from our Milky Way galaxy suggest it originated from a magnetar, which is a city-sized dense neutron star with an incredibly powerful magnetic field. On the other hand, the origin of very distant cosmological fast radio bursts remains unknown. And the latest sightings are causing scientists to question what they think they knew about them.
“These observations have taken us back to the drawing board,” said Zhang, who is also the founding director of the UNLV Astrophysical Center in Nevada. “It is clear that FRBs are more mysterious than we imagined. To further reveal the nature of these objects, additional multiwave observational campaigns are needed.”
What makes the latest observations surprising to scientists is the irregular, short-term changes in the so-called “Faraday rotation measure,” which is the magnetic field strength and particle density near the FRB source. The variations waxed and waned during the first 36 days of observations and abruptly stopped during the last 18 days before the source went out.
“I equate it to filming a film about the environment of an FRB source, and our film showed a complex, dynamic, magnetized environment that was unimaginable before,” Zhang said. “Such an environment is not directly expected for an isolated magnetar. Something else might be in the vicinity of the FRB engine, possibly a binary companion,” Zhang added.
To observe the parent galaxy FRB, the team also used the 10-meter Keck telescopes located in Mauna Kea in Hawaii. Zhang says that young magnetars are thought to be in active star-forming regions of a star-forming galaxy, but optical imaging of the host galaxy shows that – unexpectedly – the host galaxy is a metal-rich, barred spiral galaxy like our own Milky Way. . The location of the FRB is in a region where there is no significant star formation activity.
“This location is incompatible with a young magnetar central thruster formed during an extreme explosion such as a long gamma-ray burst or hyperluminous supernova, which are widely believed to be the progenitors of active FRB thrusters,” Dong said.
The study “Source of fast radio bursts in a complex magnetized place in a barred galaxy” appeared on September 21 in the journal Nature and includes 74 co-authors from 30 institutions. In addition to UNLV, Peking University, and the National Astronomical Observatory of China, collaborating institutions also include the Purple Mountain Observatory, Yunnan University, Caltech Berkeley, California Institute of Technology, Princeton University, the University of Hawaii, and other institutions from China, the United States, Australia, Germany, and Israel .
Astronomers find clues to fast radio bursts
H. Xu et al., Source of Fast Radio Bursts in a Complex Magnetized Location in a Barred Galaxy, Nature (2022). DOI: 10.1038/s41586-022-05071-8
Courtesy of the University of Nevada, Las Vegas.
Quote: Astronomers Unveil New and Mysterious Features of Mysterious Fast Radio Bursts (September 22, 2022) retrieved September 22, 2022 from https://phys.org/news/2022-09-astronomers-unveil-newand-puzzlingfeatures-mysterious.html .
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