The cause of mysterious quick radio bursts could be unexpected.

Among the most peculiar signals we detect from space are fast radio bursts. They can outshine entire galaxies in radio light during their brief duration of a few thousandths of a second. One major question persisted for years: what kind of entity could produce something so loud and quick, sometimes repeatedly?

A significant piece of the puzzle has now been added by a lengthy series of telescopic observations. The main concept is straightforward. There are other origins of these recurring rapid radio bursts in space.

A signal pointing to two stars

The current study focuses on FRB 220529A, a repeating source that is situated roughly 2.5 billion light-years away. Astronomers kept a close enough eye on it for almost 20 months to notice a unique shift in the radio signal. Only if the burst source is located in an untidy, busy neighbourhood could the type of change that was observed occur.

That area resembles a binary stellar system, in which two stars revolve around one another. The recurring source appears to share its space with a close partner star that has the ability to disturb its surroundings, as opposed to an isolated star firing bursts into empty space.

An international team used Guizhou's Five-hundred-meter Aperture Spherical Telescope (FAST) to conduct the observations. FAST, also known as the "China Sky Eye," is enormous, measuring over 1,640 feet in diameter. To bolster the outcome, the scientists also made use of Australia's Parkes radio telescope.

Strange behaviour in a radio wave

Linear polarisation, a characteristic of fast radio bursts, is the nearly perfect alignment of radio waves in a single direction. The angle of that polarisation can rotate as those waves pass through hot, charged gas that is laced with magnetic fields.

The rotation measure, or RM, is a tool used by scientists to quantify that impact. The team witnessed RM swing wildly for FRB 220529A in late 2023 before settling back down. This brief, acute incident is referred to by the team as a "RM flare." It functions as a fingerprint of the substance the radio waves travelled through before arriving on Earth.

The initial author of the study is Dr. Ye Li of Purple Mountain Observatory and the University of Science and Technology of China. "We found an abrupt RM increase by more than a factor of a hundred near the end of 2023," Dr. Li stated. "Over the course of two weeks, the RM rapidly declined and returned to its previous level."

Why the data fits a companion star

Such a rapid shift implies that a dense cloud of magnetised plasma momentarily crossed Earth's line of sight with the burst source. The group connects that plasma to a neighbouring companion star's coronal mass ejection, or CME. CMEs are massive charged particle outbursts that stars, like our Sun, can launch into space.

Professor Bing Zhang, the founding head of the Hong Kong Institute for Astronomy and Astrophysics at the University of Hong Kong HKU, stated that "one natural explanation is that a nearby companion star ejected this plasma." The team's model effectively interprets the observations, according to Yunnan University professor Yuanpei Yang.

"CMEs launched by the Sun and other Milky Way stars are consistent with the necessary plasma clump."

Patience is rewarded by repeated radio explosions.

Although they are uncommon, repeating rapid radio bursts are extremely valuable to researchers because they allow telescopes to observe the same source over time. Only after months of observation might patterns emerge, particularly if the bursts interact with shifting material surrounding the source.

Since 2020, FRB 220529A has been a part of a special FAST program that monitors recurring sources. It didn't stick out for a time. According to Professor Zhang, "FRB 220529A was monitored for months and initially appeared unremarkable." "Then, something really exciting happened after a 17-month long-term observation."

Connecting rapid radio bursts to magnetars

The latest finding supports a theory that many astronomers already take seriously: at least some fast radio bursts could be caused by magnetars. The ultra-dense remnant left over when a huge star explodes is called a magnetar, a form of neutron star with a magnetic field powerful enough to alter the surrounding universe.

Another star may release plasma into the vicinity of a magnetar, altering the appearance of the burst signal as it departs. According to Professor Zhang, "this finding provides a definitive clue to the origin of at least some repeating FRBs." "The evidence strongly supports a binary system consisting of a star similar to our Sun and a magnetar, which is a neutron star with an extremely strong magnetic field."

The team attributes the outcome to extensive, meticulous observation time and perseverance across several institutions. Professor Xuefeng Wu of Purple Mountain Observatory claims that the discovery was made possible by persistent observations performed using the best telescopes in the world as well as the unceasing efforts of a committed research team.