Astronomers link 10-minute X-ray burst to neutron star merger 6 billion light-years away

September 30, 2026 at 02:42 PM2 min

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Astronomers have obtained the first convincing evidence that fast X-ray bursts can arise from neutron star collisions. The Einstein Probe telescope detected a nearly 10-minute X-ray burst, EP250704a/GRB 250704B, at redshift z=0.6610. Follow-up observations with ESO's Very Large Telescope revealed absorption lines of iron and magnesium, ruling out a supernova.

Key Facts

The X-ray burst EP250704a/GRB 250704B lasted nearly 10 minutes and was detected by the Einstein Probe telescope.
Spectroscopic observations with ESO's Very Large Telescope measured the burst's redshift at z=0.6610, corresponding to a distance of over 6 billion light-years.
Absorption lines of iron and magnesium were detected in the burst's spectrum, and no supernova was found at the location.
The event is interpreted as the merger of two neutron stars, possibly leaving behind a magnetar that powered the prolonged X-ray emission.

Detection and Follow-up

The Einstein Probe, a European-Chinese X-ray telescope, detected the burst EP250704a/GRB 250704B. Within minutes, astronomers began observations with ESO's Very Large Telescope in Chile and other observatories. The X-shooter spectrograph on the VLT dispersed the burst's light and revealed absorption lines of iron and magnesium. The measured redshift of z=0.6610 places the source at a distance of more than six billion light-years.

Interpretation as Neutron Star Merger

A search for a supernova at the burst location found none, ruling out that alternative explanation. The nearly 10-minute duration and the measured distance point instead to a merger of two neutron stars. Neutron stars are ultra-dense remnants of massive stars, and their collisions release enormous energy and gravitational waves. Researchers suggest the merger may have produced a magnetar, a rapidly spinning neutron star with an extremely strong magnetic field. Such a magnetar could power the unusually prolonged X-ray emission observed in EP250704a.

Implications for Future Observations

Previously, short gamma-ray bursts lasting less than two seconds were considered the main electromagnetic signature of neutron star mergers. EP250704a shows that such events can produce significantly longer X-ray emission. Future gravitational-wave astronomy could help link neutron star mergers to X-ray signals and precisely localize these events.