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Astronomers Detect Highly Variable Magnetic Field around Source of Repeating Fast Radio Burst

The highly variable magnetic field around the source of FRB 20190520B. Image credit: Di Li / ScienceApe / CAS.Galaxy

“Our findings bring us closer to solving the enigma of FRBs and help us to uncover new insights into some of the most extreme environments in the Universe,” said Dr. Shi Dai, an astronomer at Western Sydney University, the National Astronomical Observatories at the Chinese Academy of Sciences and CSIRO.

“We know that FRBs originate from sources in distant galaxies. This makes FRBs unique tools to probe a range of astrophysics, such as missing matter in between galaxies, the expansion of the Universe, and astrophysics in dense and highly magnetised environments.”

Dr. Dai and colleagues observed the repeating FRB 20190520B over a 17-month period using CSIRO’s Parkes radio telescope and the Green Bank Telescope.

They found that the source of FRB 20190520B is surrounded by dense plasma that is not only highly magnetised but also highly turbulent, with the direction of the magnetic field changing twice during this period — a phenomenon never observed before.

“FRB 20190520B is one of a rare class of FRBs found to repeat,” Dr. Dai said.

“First discovered by the FAST telescope, FRB 20190520B is not only active but more importantly can be detected over a wide radio frequency window, which enables us to use the most advanced radio instruments, such as Parkes and its ultra-wideband receiver, to carry out detailed studies.”

Over the course of the study, the astronomers detected more than 100 bursts from FRB 20190520B, and successfully detected polarised emission in 13 bursts.

Significantly, these polarised bursts revealed the direction of a magnetic field around the source of FRB 20190520B changed twice during this short period of time.

“A total of 113 bursts from FRB 20190520B were detected by the Parkes radio telescope, exceeding the sum of the number of fast radio bursts previously discovered at Parkes, accentuating the value of FRB 20190520B,” Dr. Dai said.

“Our interpretation of the finding is connected to changes in the parallel component of the integrated magnetic field along the line-of-sight, including reversals,” said Western Sydney University’s Professor Miroslav Filipovic.

“The change of the direction of the magnetic field put some strong constraints on the origin of this FRB.”

“It requires that the source of FRB is moving relative to a large-scale magnetic field.”

“One of the possibilities that we proposed is that the FRB source is a binary system with a star, which has strong stellar wind with a strong magnetic field.”

“As the FRB source orbits the star, it moves in and out from the wind, which can explain our observations.”

The astronomers now plan to conduct further observations of the FRB utilising the Parkes radio telescope and other instruments to better understand the object’s nature.

“The binary-system model for FRBs can be tested with future observations since we expect the observational features to repeat periodically if the source really is in a binary system,” Dr. Dai said.

“Our work delivered one of the clearest pictures of the source of fast radio bursts, which will have profound implications on our understanding of FRBs and their origin.”

Category: Technology

Source: Sci News

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