Science

Milky Way Magnetar Makes Fast Radio Burst – Sky & Telescope

An artist’s concept of a magnetar, a highly magnetized neutron star
NASA’s Goddard Space Flight Center / S. Wiessinger

Two observatories have independently detected a burst of radio waves coming from a magnetar within the Milky Way.

The flash of radio waves looks just like the fast radio bursts (FRBs) discovered in increasing numbers over the past few years — but always in other galaxies. These flashes unleash a vast amount of power in the blink of an eye, producing as much energy in milliseconds as the Sun produces in a day. But what causes them remains unknown. The new detection, not yet published but posted on The Astronomer’s Telegram, promises to shed light on a powerful mechanism.

A Milky Way Magnetar

Magnetars are the dead cores of stars that collapsed when the star itself went supernova. In this sense, they form the same way neutron stars do. But in magnetars, the core retains a powerful magnetic field, typically with a strength of a thousand trillion Gauss. (For comparison, Earth’s magnetic field is less than a Gauss on our planet’s surface.)  These exotic objects successfully explain weird phenomena, such as sources that flash and sputter gamma rays and X-rays.

Now, new observations suggest that magnetars may be responsible for at least some of the til-now mysterious FRBs, which currently number over 100.

A magnetar in our own galaxy, known as SGR 1935+2154, was already in fine form, dishing out multiple X-ray flashes as seen with the NICER instrument aboard the International Space Station, the Neil Gehrels Swift Observatory, and others. The magnetar had been discovered in 2014 and monitored since then.

But on April 28th, something happened, and the magnetar emitted a powerful radio burst. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the STARE2 radio array both observed the distinctive flash of radio waves. Nearly simultaneously, the magnetar burped out a short X-ray flash spotted with the Chinese Insight X-ray telescope.

Magnetar fast radio burstRadio spectrum of the double-peaked fast radio burst coming from a magnetar within our own galaxy.
P. Scholz et al. / Astronomer’s Telegram

The Chinese FAST radio dish later spotted another, much quieter burst on April 30th. The multiple independent detections are important, because they help astronomers pinpoint a more exact location of the burst.

“The luminosity implied by the STARE analysis is really astounding,” says Geoffrey Bower (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan). “It does suggest that bursts from magnetars could be detected at enormous distances.”

Do Magnetars Solve the Fast Radio Burst Problem?

“This new discovery, if it holds up, is a proof that magnetars can produce the relevant kind of luminosities,” Bower explains.

The discovery could also help astronomers understand what’s responsible for powering the radio-wave bursts. Snapping and reconnecting magnetic field lines around the Sun produce powerful solar storms; around a magnetar, such disruptive reorganization of the magnetic field could cause the radio bursts we see.

Nevertheless, Bower hastens to add that this doesn’t mean that all FRBs are magnetars. “There may very well be other mechanisms or sources at work producing FRBs. We see a lot of different phenomenologies . . . it’s not necessary that it be explained with one model.”

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