Unveiling the secrets of fast radio bursts, a cosmic mystery, has led to a fascinating discovery. These bursts, lasting mere milliseconds, are incredibly powerful, outshining entire galaxies in radio emissions. For years, astronomers have wondered about the source of such intense and rapid signals.
Now, a groundbreaking study has revealed a key piece of the puzzle. Some of these repeating fast radio bursts are not solitary events; they occur in the presence of a stellar companion.
The focus of this research is a repeating source, FRB 220529A, located approximately 2.5 billion light-years away. Over an extensive observation period of nearly 20 months, astronomers witnessed a rare change in the radio signal, indicating a dynamic and active environment. This environment resembles a binary stellar system, where two stars orbit each other.
Imagine a star, not alone in the vastness of space, but with a partner, stirring up the surroundings. This is precisely what the observations suggest. The repeating source, FRB 220529A, appears to be in the company of a nearby star, influencing the environment and potentially triggering these bursts.
The study, led by an international team using the Five-hundred-meter Aperture Spherical Telescope (FAST) in Guizhou, China, also known as the "China Sky Eye," provides a unique perspective. With its massive 1,640-foot dish, FAST, along with support from Australia's Parkes radio telescope, captured a rare glimpse into this cosmic phenomenon.
Fast radio bursts are known for their linear polarization, with radio waves aligned in a single direction. As these waves travel through charged gas and magnetic fields, their polarization can rotate, an effect measured as rotation measure (RM). In late 2023, the team observed a dramatic swing in RM for FRB 220529A, followed by a rapid decline. This "RM flare" is like a fingerprint, revealing the material through which the radio waves passed before reaching Earth.
Dr. Ye Li, the study's first author from the Purple Mountain Observatory and the University of Science and Technology of China, explained, "We detected an abrupt RM increase, over a hundred times its previous level, near the end of 2023. It then quickly returned to its initial state within two weeks."
The team suggests that this rapid change indicates the presence of a dense cloud of magnetized plasma, briefly crossing the line of sight between Earth and the burst source. This plasma is linked to a coronal mass ejection (CME) from a nearby companion star, a massive eruption of charged particles that stars, including our Sun, can release into space.
Professor Bing Zhang, founding director of the Hong Kong Institute for Astronomy and Astrophysics at the University of Hong Kong HKU, elaborated, "A natural explanation is that a nearby companion star ejected this plasma."
Professor Yuanpei YANG of Yunnan University added, "Our model aligns well with the observations, and the required plasma clump is consistent with CMEs launched by stars in the Milky Way."
Repeating fast radio bursts are rare but invaluable to researchers, as they allow telescopes to observe the same source over extended periods. Patterns may emerge after months of monitoring, especially when the bursts interact with changing material surrounding the source.
FRB 220529A was part of a dedicated FAST program, tracking repeating sources since 2020. Initially, it appeared unremarkable, but patience paid off.
"FRB 220529A was monitored for months and seemed ordinary at first," said Professor Zhang. "But after a long-term observation of 17 months, something extraordinary occurred."
This new finding supports the idea that magnetars, a type of neutron star with an incredibly strong magnetic field, could be behind at least some fast radio bursts. When a magnetar is part of a binary system with another star, the partner star can inject plasma into the area, altering the burst signal.
"This discovery provides definitive evidence for the origin of some repeating FRBs," added Professor Zhang. "The evidence strongly points to a binary system containing a magnetar and a star similar to our Sun."
The team attributes their success to the dedication and perseverance of multiple facilities, allowing for extended observation periods.
Professor Xuefeng Wu of Purple Mountain Observatory emphasized, "This discovery was made possible by the unwavering commitment of the research team and the use of the world's best telescopes."
The full study was published in the prestigious journal Science, offering a deeper understanding of these mysterious cosmic events.
