Gamma-ray burst from magnetar lights up star-forming galaxy

Astronomers have witnessed a rare giant flare from a magnetar about 12 million light-years away.

Such events release huge amounts of energy in the form of gamma rays and are therefore known as gamma-ray bursts (GRBs). These GRBs usually last less than a second and originate from neutron stars – the dense remains of a dead giant star’s core.

Starburst galaxy messier 82
Starburst galaxy Messier 82 imaged by Hubble. Credit: NASA, ESA and the Hubble Heritage Team | Acknowledgment: J. Gallagher, M. Mountain and P. Puxley.

Magnetars are a type of highly magnetised neutron star. GRBs from these stars are extremely rare. They’ve only been seen 3 times from magnetars in our galaxy or the nearby Large Magellanic Cloud in about 50 years.

The new burst, named GRB 231115A, occurred in the galaxy Messier 82 (M82), according to research published in Nature.

M82 is known as a starburst galaxy because it is undergoing rapid star formation. Magnetars are typically seen in such star-forming regions.

Pinpointing which GRBs emanate from magnetars isn’t easy.

“A few short GRBs have been proposed, with different amounts of confidence, as candidate giant magnetar fares in nearby galaxies,” the authors note.

Observations of GRB 231115A including the length of the burst, X-ray and optical data taken after the burst and the lack of other signals such as gravitational waves “unambiguously qualify this burst as a giant flare from a magnetar in M82,” according to the researchers.

The findings point to starburst galaxies as promising targets for studying giant flares, helping astronomers understand the mechanisms behind mysterious GRBs in the universe.

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