Astronomers have linked a nearly ten-minute X-ray flash to the collision of two neutron stars — likely witnessing the birth of a magnetar.

The event, EP250704a/GRB 250704B, was spotted on July 4, 2025. Its gamma-ray burst lasted half a second, but the Einstein Probe satellite recorded bright X-rays for nearly ten minutes — the longest such flash ever seen from a neutron-star merger.

Eleonora Troja’s team followed up with the Very Large Telescope and the Very Large Array, pinning the explosion to a redshift of 0.6610. The findings, published in Science Bulletin, suggest the merger left behind a rapidly spinning, intensely magnetic neutron star.

“When I saw the X-ray data from this new event, I realized something was up,” Troja said. Graduate student Niccolo Passaleva called it “a front-row seat to the most extreme forces of the universe”.

A separate study led by Hong Kong researchers found similar hidden X-ray phases after other mergers. The discoveries could help explain mysterious cosmic flashes seen for decades.