Astronomers find clues to source of fast radio bursts

　　An aerial view of FAST. [Photo/Xinhua]

BEIJING -- An international group of astronomers has conducted a 17-month-long study of a repeating fast radio burst (FRB) from a distant galaxy, revealing that it reversed its magnetic field twice, providing clues as to its origins.

The magnetic reversal may indicate that the FRB source orbits in a binary star system, and the companion star may be a black hole or a massive star, the scientists said in a paper published in the journal Science on Friday.

The brightest radio bursts known in the universe, FRBs are very short transients, only several milliseconds in duration. However, their precise origins are unclear and the subject of ongoing research.

Scientists from the National Astronomical Observatories under the Chinese Academy of Sciences, in collaboration with their overseas counterparts, targeted a repeating FRB, coded FRB 20190520B, which was discovered by the FAST telescope, or the "China Sky Eye."

The team monitored the FRB with telescopes located in Australia and the United States for 17 months, detecting hundreds of bursts from it. They found that the FRB's Faraday rotation measure -- an indicator of its magnetic field strength -- was highly variable and twice reversed direction.

Team member Feng Yi, from the research institute Zhejiang Lab, said, "This shows that there is an extreme reversal of the magnetic field around it, which means that FRB 20190520B may be in a binary star system, and the companion star of the binary system may be a black hole or a massive star."

Understanding such changes in the magnetized environment around FRBs is an important step forward and is expected to help further clarify their origins, said Feng.