An international team of researchers has revealed new evidence about the nature of mysterious fast radio bursts (FRBs), objects in space that generate brief, intense flashes of radio waves from distant galaxies.
Astronomers from Cornell University, West Virginia University, Caltech, Western Sydney University and Australia’s national science agency CSIRO contributed to the study, which for the first time shows the existence of a reversible magnetic field around an FRB.
Published today in Science are observations of a repeating fast radio burst known as 20190520B over a 17-month period using the Green Bank Telescope in West Virginia and the Parkes radio telescope at CSIRO in Australia .
The study found that FRB 20190520B is surrounded by a dense plasma that is not only highly magnetized but also highly turbulent, during which the direction of the magnetic field changes twice—a phenomenon that has never been observed before.
“The dramatic changes in magnetic field strength and radio wave scattering observed over several months indicate the complex and dynamic environment of this extraordinary source of repeating fast radio bursts,” said co-author Dr Shami Chatterjee. ’03, Research Professor of Astronomy in the College of Arts and Sciences. “These new observations are another step forward in understanding the extraordinary engine and diversity of fast radio bursts.”
FRBs were first discovered by astronomers using the Parkes telescope in 2007, and have since become one of the most active areas of research in modern astrophysics. However, despite enormous efforts, scientists are still unsure of their exact origin.
“We know that FRBs originate from sources in distant galaxies,” said lead co-author Dai Shi of Western Sydney University. “This makes fast radio bursts a unique tool for exploring a range of astrophysics, such as ‘missing’ matter between galaxies, the expansion of the universe, and astrophysics in dense and highly magnetized environments.”
“We’ve been studying this particular FRB source for years, and it continues to amaze us,” said co-author Stella Ocker, a Cornell doctoral student in astronomy. “In addition to these extreme magnetic field reversals, FRB 20190520B also shows a lot of scattering from its local environment. The scattering tracks fluctuations in the density of the gas around the source of the FRB, and our team at Cornell found the scattering from this FRB to be very unusual.” “
Ocker was the lead author of a paper published earlier this year in MNRAS reporting that their team found that the scattering of FRB 20190520B varies dramatically on timescales of minutes. Never before has such a rapid change in scattering been observed from a FRB.
“This new discovery of a magnetic field reversal further enriches our understanding of the extremely complex, dynamic gas systems surrounding the source of the FRB,” Ocker said. “Ultimately, we hope that continuing to monitor the magnetic field and scattering properties of this FRB will allow us to Determine its physical origin.”
During the course of the study, the research team detected more than 100 bursts from FRB 20190520B, and successfully detected polarized emission in 13 bursts. Remarkably, these bursts of polarization revealed two changes in the direction of the magnetic field around the source of FRB 20190520B within a short period of time.
“One possibility we raise is that the FRB source is a binary star system with a star that has a strong stellar wind and a strong magnetic field. As the FRB source orbits the star, it is blown in and out with the wind, which could explain our observations,” said co-author Miroslav Filipovic of Western Sydney University.
The researchers are now planning further observations of the FRB with instruments including the Green Bank Telescope, China’s FAST Telescope and Australia’s Parkes Telescope to better understand the nature of the object.
This story also appears on the College of Arts and Sciences website.
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