A Unified Explanation for Fast Radio Bursts

A discovery that linked a fast radio burst to a magnetar in the Milky Way showed that certain fast radio bursts come from magnetars. A new study explores whether all fast radio bursts could have magnetar origins.

Varied Bursts

Fast radio bursts — extremely bright radio blips lasting anywhere from a fraction of a millisecond to a few seconds — have provided researchers with one of the best recent astronomical mysteries. What causes these brilliant radio flashes, and why are they so varied? Most fast radio bursts seem to happen just once, while others repeat frequently or infrequently on irregular or regular timescales.

In July 2020, astronomers reported the discovery of a fast radio burst likely associated with a magnetar in the Milky Way. This discovery suggested that at least some fast radio bursts come from magnetars, the rapidly spinning, intensely magnetized remnants of certain massive stars. However, it’s still not known whether all fast radio bursts share this origin, or if their varied behaviors can be traced to equally varied origins.

Mystery Solved by Magnetars?

In a recent research article, Bing Zhang (University of Hong Kong; University of Nevada) and Rui-Chong Hu (University of Nevada) set out to explore the possibility that all fast radio bursts have magnetar origins.

Zhang and Hu examined the different pathways through which magnetars form, as well as what properties they tend to have in each of these scenarios. This analysis suggested that the vast majority of magnetars in our universe are singletons, having formed from isolated stars, disrupted binary systems, or stellar mergers. This aligns with observations of magnetars in the Milky Way, none of which appear to have companions.

The remaining few percent of magnetars reside in binary systems. These coupled-up magnetars largely have companions more than twice as massive as the Sun, though some are paired with helium stars or compact objects.

Multiple Possible Arrangements

Zhang and Hu found that both isolated and paired-up magnetars tend to form with their spin and magnetic axes in close alignment — a setup that likely enables the production of rapid-fire fast radio bursts. For isolated magnetars, these axes may become misaligned over time, sapping their ability to produce repeated bursts. In binary systems, magnetars that accrete mass from the stellar winds of a companion likely retain their alignment, creating a long-lasting engine of repeating fast radio bursts. The presence of winds from a stellar companion may also explain several curious traits of some fast radio bursts, such as rapid changes in polarization angle.

In this framework, actively repeating fast radio bursts arise from aligned magnetars in binary systems, while one-off or infrequently repeating bursts come from isolated magnetars or misaligned magnetars in binary systems. Isolated magnetars could also be responsible for some actively repeating bursts, though this ability is likely short lived.

Though this work demonstrates that magnetars could be the source of all fast radio bursts, it doesn’t rule out the possibility that fast radio bursts have diverse origins instead. Further work is needed to explore other pathways and make even more headway on the mystery of fast radio bursts.

Citation

“Magnetars in Binaries as the Engine of Actively Repeating Fast Radio Bursts,” Bing Zhang and Rui-Chong Hu 2025 ApJL 994 L20. doi:10.3847/2041-8213/ae1023