Record-Breaking Ten-Minute X-Ray Flash Points to Magnetar Birth After Neutron Star Collision

A ten-minute X-ray flash recorded on July 4, 2025, and designated EP250704a/GRB 250704B, is the longest prompt X-ray emission ever seen from a neutron-star merger. Detected by the SVOM, Insight-HXMT and Einstein Probe satellites, the burst’s gamma-ray component lasted only about half a second, while the X-ray glow persisted for nearly ten minutes. Rapid follow-up with the European Southern Observatory’s VLT and the VLA allowed scientists to measure a redshift of z=0.6610, confirming the source lies more than six billion years distant, and to rule out a supernova origin.

Led by Eleonora Troja’s team, the researchers argue the data indicate the creation of a magnetar - a fast-spinning neutron star with an extreme magnetic field - as the merger remnant. This finding opens the possibility of using long-lasting X-ray flashes to identify magnetar-forming mergers and to better gauge how often such events occur, especially when paired with future gravitational-wave detections.