X-ray fireworks linked to rapid radio bursts

For more than a decade, astronomers have puzzled over observations of millisecond-long radio signals called fast radio bursts. In recent years, research has suggested that these bursts may come from magnetars, a type of neutron star with a magnetic field about a thousand trillion times stronger than Earth’s. However, the mechanism by which magnetars produce fast radio bursts remains unclear. Now, Andrei Beloborodov of Columbia University has theoretically investigated the interaction between the strong electromagnetic waves from a radio burst and the magnetized particles around a magnetar. [1]† He found that the radio waves scatter off the particles more strongly than previously thought, which could inform models seeking to narrow down the origin and location of fast radio bursts.

In the region of space immediately surrounding a magnetar, a fast radio burst can be modeled as an electromagnetic wave immersed in a magnetic field. When the strength of the magnetic field is much greater than the amplitude of the radio wave – as is the case near the surface of a magnetar – the wave is predicted to be minimally scattered by the plasma. But this condition no longer applies once the radio burst propagates some distance from the magnetar. Instead, the amplitude of the wave becomes much larger than the magnetic field.

In that regime, Beloborodov discovered that the electromagnetic wave undergoes strong scattering. This scattering can hinder the escape of the radio burst because it causes the wave to lose energy drastically. Wave scattering also generates large amounts of electron-positron pairs which are then accelerated by the electromagnetic waves. This process causes the pairs to emit X-ray “fireworks.” Astronomers could potentially observe these fireworks to narrow down models of fast radio bursts.

—Sophia Chen

Sophia Chen is a freelance science writer based in Columbus, Ohio.

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